BAIRD, Mark Stephen (Bangor University, Dainiol RoadBangor, Gwynedd LL57 2UW, GB)
DE BRAGANÇA, Radek Messias (Bangor University, Deiniol RoadBangor, Gwynedd LL57 2UW, GB)
BAIRD, Mark Stephen (Bangor University, Dainiol RoadBangor, Gwynedd LL57 2UW, GB)
| CLAIMS 1. A method for the fractionation of cashew nut shell liquid, comprising solvent- solvent extraction using a polar solvent component and a non-polar, non-acidic, non-basic solvent component; wherein the polar solvent component is a mixture comprising: i) a first solvent comprising a fhiorinated solvent; and ii) a second solvent comprising a solvent satisfying the following parameters: a) Hildebrand parameter greater than 10 (kcal dnf3)0,5 and b) dipolarity/polarizability (π), hydrogen bond acidity (a), and hydrogen bond basicity (β) having the following relationship: α/(α + β + π) > 0.5; β/(α + β + π) < 0.8; and π /(α + β + π) > 0.3. 2. A method according to claim 1, wherein the cashew nut shell liquid comprises natural cashew nut shell liquid. 3. A method according to claim 2, wherein the natural cashew nut shell liquid is fractionated to provide anacardic acid and cardol. 4. A method according to claim 1, wherein the cashew nut shell liquid comprises technical cashew nut shell liquid. 5. A method according to claim 4, wherein the technical cashew nut shell liquid is fractionated to provide cardanol and cardol. 6. A method according to any preceding claim, wherein the first solvent comprises one or more of the following in any combination: fluoroalcohols, fluoroamines and nitrofluorinated solvents. 7. A method according to claim 6, wherein the first solvent comprises one or more of the following in any combination: trifluoroethanol, fluorophenols, fluroxene, enflurane, isoflurane, methoxyflurane and hexafluoro-2-propanol. 8. A method according to claim 7, wherein the first solvent comprises trifluoroethanol. 9. A method according to any preceding claim, wherein the second solvent comprsies one or more of the following in any combination: dimethylformamide, acetonitrile, diethylene glycol, nitromethane, dimethylsulfoxide, cyanopropane, nitroethane, N-methylpyrrolidinone and benzonitrile. 10. A method according to claim 9, wherein the second solvent comprises acetonitrile and/or nitromethane. 11. A method according to any preceding claim, wherein the non-polar, non-acidic, non-basic solvent component comprises an aliphatic solvent. 12. A method according to claim 11, wherein the aliphatic solvent comprises an alkane and/or isoalkane. 13. A method according to claim 12, wherein the aliphatic solvent comprises one or more of the following in any combination: pentane, hexane, heptane and octane. 14. A method according to claim 11 or claim 12, wherein the aliphatic solvent comprises petrol. 15. A method according to any preceding claim, wherein the solvent-solvent extraction comprises counter-current extraction. 16. A method of production of anacardic acid and/or cardol from natural cashew nut shell liquid, comprising fractionating the natural cashew nut shell liquid by solvent-solvent extraction using a polar solvent component and a non-polar, non-acidic, non-basic solvent component; wherein the polar solvent component is a mixture comprising: i) a first solvent comprising a fluorinated solvent; and ii) a second solvent comprising a solvent satisfying the following parameters: a) Hildebrand parameter greater than 10 (kcal dm ) ' and b) dipolarity/polarizability (π), hydrogen bond acidity (a), and hydrogen bond basicity (β) having the following relationship: α/(α + β + π) > 0.5; β/(α + β + π) < 0.8; and π /(α + β + π) > 0.3. 17. A method of production of cardanol and/or cardol from technical cashew nut shell liquid, comprising fractionating the technical cashew nut shell liquid by solvent-solvent extraction using a polar solvent component and a non-polar, non-acidic, non-basic solvent component; wherein the polar solvent component is a mixture comprising: i) a first solvent comprising a fluorinated solvent; and ii) a second solvent comprising a solvent satisfying the following parameters: a) Hildebrand parameter greater than 10 (kcal dm ) ' and b) dipolarity/polarizability (π), hydrogen bond acidity (a), and hydrogen bond basicity (β) having the following relationship: α/(α + β + π) > 0.5; β/(α + β + π) < 0.8; and π /(α + β + π) > 0.3. 18. A solvent mixture for use in the fractionation of cashew nut shell liquid by solvent- solvent extraction, wherein the solvent mixture comprises: i) a first solvent comprising a fluorinated solvent; and ii) a second solvent comprising a solvent satisfying the following parameters: a) Hildebrand parameter greater than 10 (kcal dm ) ' ; and b) dipolarity/polarizability (π), hydrogen bond acidity (a), and hydrogen bond basicity (β) having the following relationship: α/(α + β + π) > 0.5; β/(α + β + π) < 0.8; and π /(α + β + π) > 0.3. 19. A solvent mixture according to claim 18, wherein the first solvent comprises one or more of the following in any combination: fluoroalcohols, fluoroammes and nitrofluorinated solvents. 20. A solvent mixture according to claim 19, wherein the first solvent comprises one or more of the following in any combination: trifluoroethanol, fluorophenols, fluroxene, enflurane, isoflurane, methoxyflurane and hexafluoro-2-propanol. 21. A solvent mixture according to claim 20, wherein the first solvent comprises trifluoroethanol. 22. A solvent mixture according to any one of claims 18 to 21, wherein the second solvent comprsies one or more of the following in any combination: dimethylformamide, acetonitrile, diethylene glycol, nitromethane, dimethylsulfoxide, cyanopropane, nitroethane, N-methylpyrrolidinone and benzonitrile. 23. A solvent mixture according to claim 22, wherein the second solvent comprises acetonitrile and/or nitromethane. 24. A solvent mixture according to any one of claims 18 to 23, wherein the cashew nut shell liquid comprises natural cashew nut shell liquid. 25. A solvent mixture according to claim 24, wherein the natural cashew nut shell liquid is fractionated to provide anacardic acid and cardol. 26. A solvent mixture according to any one of claims 18 to 23, wherein the cashew nut shell liquid comprises technical cashew nut shell liquid. 27. A solvent mixture according to claim 26, wherein the technical cashew nut shell liquid is fractionated to provide cardanol and cardol. 28. The use of a solvent mixture according to any one of claims 18 to 27 in the fractionation of cashew nut shell liquid by solvent-solvent extraction. 29. The use of a solvent mixture in the fractionation of cashew nut shell liquid by solvent- solvent extraction, wherein the solvent mixture comprises: i) a first solvent comprising a fluorinated solvent; iii) a second solvent comprising a solvent satisfying the following parameters: a) Hildebrand parameter greater than 10 (kcal dm ) ' ; and b) dipolarity/polarizability (π), hydrogen bond acidity (a), and hydrogen bond basicity (β) having the following relationship: α/(α + β + π) > 0.5; β/(α + β + π) < 0.8; and π /(α + β + π) > 0.3. 30. The use according to claim 28 or claim 29, wherein the solvent mixture is used with a non-polar solvent in the solvent-solvent extraction. 31. The use according to claim 30, wherein the non-polar solvent comprises a non- polar, non-acidic, non-basic solvent. 32. The use according to claim 31, wherein the non-polar, non-acidic, non-basic solvent component comprises an aliphatic solvent. 33. The use according to claim 32, wherein the aliphatic solvent comprises an alkane and/or isoalkane. 34. The use according to claim 33, wherein the aliphatic solvent comprises one or more of the following in any combination: pentane, hexane, heptane and octane. 35. The use according to claim 32 or claim 33, wherein the aliphatic solvent comprises petrol. 36. A method of producing of low viscosity cashew nut shell liquid from cashew nut shell liquid, comprising solvent-solvent extraction to flocculate impurities in the cashew nut shell liquid, and removal of the flocculated impurities. 37. A method according to claim 36, wherein the cashew nut shell liquid comprises technical cashew nut shell liquid. 38. A method according to claim 36 or claim 37, wherein the solvent-solvent extraction is carried out using a mixture of nitromethane or acetonitrile with petrol. |
The present application relates to the fractionation of cashew nut shell liquid (CNSL).
3- Alkenyl salicylic acids (1) (also called gingkolic acids or anacardic acids), while 3-alkenylresorcinols (2) (also called resorcinolic lipids or bilobols or cardols) are non- isoprenoic phenols.
R 0 -alkenyl chain
These families of compounds present distinctive biological activities (both mediate DNA scission (Furstner A, Seidel G, J. Org. Chem., 1997, 62, 2332-2336) and a range of enzyme activities).
Anacardic acids inhibit prostaglandin synthase (Kubo, I., Chem. Letters, 1987, 1101-1104), glycerol-3 -phosphate dehydrogenase (the inhibition of this enzyme is related with prevention of triglyceride accumulation in cells) (Rejman,J., Kozubek,A., Cell Mol. Biol. Lett., 1997, 2, 4, 411-419), glucosidase and invertase (Toyomizu M., Sugiyama S., Jin RL, Nakatsu T., Phytotherapy Research, 1993, 7, 3, 252-254), tyrosinase (Kubo, I. ACS Symposium Series, 1998, 658, 311-326) hyaluronidase, and interfere with lipoxygenase oxidation (Roth, M.,Gutsche B.,Herderich, M., Humpf, H.U., Shreier, P., J. Agric. Food Chem., 1998, 46, 2951-2956), and have bactericide and sporicide activity.
Anacardic acids show bactericide activity against Bacillus subtilis, Escheria coli, Streptococcus mutans (the bacteria responsible for tooth decay), Propionibacterium acnes (the bacteria responsible for acne) (Kubo I, Muroi, H., Hijema M., J. Agric. Food. Chem., 1993, 41, 1016-1021), Helicobacter pilori (Kubo, J, Lee R.J., Kubo, I., J. Agric. Food Chem., 1999, 47, 533-537), Mycobacterium smegmatitis (Adawadkar, P.D., El Sohly M.A., Fitoterapia, 1981,52, 129-135.), molluscicide activity (Laurens A., Fourneau C, Hocquemiller, R., Cave A., Bories C, Loiseau PM, Phytotherapy Research, 1997, 11, 2, 145-146.) antiaflatoxigenic activity (Molyneux, R.J., Mahoney N., Campbell B.C., ACS Symposium series, 2000, 745:43-53) and sporicide activity against Colletotrichum capsici (Prithiviraj,B.,Manickam M., Singh, U.P., Ray A.B., Can.J.Bot, 1997, 75, 207-211) and against Aphanomyces cochlioides. Against the latter, anacardic acid (15:2) shows an activity similar to fluazinam, a commercial fungicide.(Begum, P., Hashidoko,Y., Islam M.T., Ogawa,Y., Tahara,S., Z. Naturforsch, 2002, 57, 874-882.).
Anacardic acids have been considered as the main cause of the resistance to aphids, spiders and small pests of pest resistant geraniums (Schultz D.J., Medford J.I.,Cox-Foster D., Grazzini R.A., Craig R., Mumma R.O., Advances in Botanical Research Incorporating Adavances in Plant Pathology, 2000, 31 : 175-192).
Anacardic acids also exhibit an uncoupling effect on oxidative phosphorylation of rat liver mitochondria' (Toyomizu, M, Okamoto, K., Teru I., Chen Z., Nakatsu T., Life Sciences, 2000, 66, 3,229-234), inhibit β-lactamase, (Hird NW, Milner PH, Bioorganic and Medicinal Chemistry Letters, 1994, 4, 12, 1423-1428) and the tissue factor (TF) Vila complex (Dandam W., Girard,T.J., Kasten T..P., LaChance, R.M., Miller- Wideman, M.A. Durley R., J.Nat.Prod., 1998, 61, 1352-1355).
Cardols have been detected recently in plants as active ingredients with cytotoxic activity (Lee J.S., Cho, Y.S., Eu J.P., Jinwoong ., Oh, W.K., Lee H.S., Ahn, J.S., J. Nat. Prod, 1998, 61, 867-871) anti-tuberculosis (Sun, W.Y.S., Zong Q, Gu RL, Pan BC Natural Product Letters, 1998, 11, 193-200) and cardiological (Roufogalis BD, Li Q, Tran VH, Kable EPW, Duke CC, Drug dev. Res. , 1999, 46, 3-4, 235-249) related properties.
Anacardic acid has reported activity as a potentiator of penicillin, (US5776919); in the prevention or treatment of coccidiosis (US5725894); and as an anti-obesity and fat reducing agent (US5240962).
Cardols have been shown to lower intra-occular pressure (US4083868) and as anti- obesity and fat reducing agents (US 5240962). Cardol (15:0) is 100 times more active than diethylcarbamazine, a drug commonly used against worms. (Suresh, M., Ray, R.K., Curr. Set, 1990, 59, 477-479). Cardols (with a 13 carbon chain) have been isolated as the active ingredient in a medicinal Chinese plant which demonstrated 80% efficiency in tuberculosis treatment. The syrup of this plant is commercial in the USA (Sun W.Y., Natural Product Letters, 1998, 11,193-200. Gonzalez, MJ.T.G., DeOliveira, C.J.C., Fernandez, J.O., Kijoa, A., Herz W., Phytochemistry, 1996, 43, 1333- 1336).
Due to the interest in these biological activities and because the availability of both anacardic acids and cardols has been poor, several syntheses of anacardic acids, cardols and analogues have been published in recent years (Alonso, E., Ramon D.J., Yus Miguel, J. Org.Chem., 1997, 62, 417-421; Tran Van H., Roufogalis B., Duke C.C., Aust.J. Chem.,
1997, 50, 747-750.; Baylis, C.J., Odle S.W.D., Tyman, J.P.H., J. Chem. Soc. Perkins 1, 1981,132-141 ; Dol, G.C., Kamer P.C.J., Van Leeuvwen, P.W.N.M., Eur. J. Org. Chem.,
1998, 359-364; Nguyen, Thi-Huu, Castanet, A-S, Mortier, ^.Organic Letters, 2006, 8, 4, 765-768; Furstner A, Seidel G, J Org. Chem., 1997, 62, 2332-2336; WO2005/122670),
Unfortunately, these methods of synthesis either have very low yields, use costly reagents, or imply a large number of synthetic steps.
Thus, a need exists for an industrially useful process for extraction of these compounds.
Both anacardic acids and cardols have been found in a number of botanical families, anacardic acids have been found in Anacardiaceae, Ginkgoaceae, and Myristiceae (Jones TH, Brunner SR, Edwards AA, et al., J. Chem., Ecology 2005, 31, 2, 407-417), while cardols have been found in Gramineae, Primulaceae, Iridaceae, Compositae, Leguminoseae, Anacardiaceae, Ginkgoaceae, and others (Kozubek, A., Tyman, JPH, Chem.Rev., 1999, 1, 1-29). However the major botanical source of this chemicals is the cashew tree (Anacardium occidentale Linn).
The cashew is a tree originally from the Amazon. Historically, the cashew tree was commonly cultivated by the Indians from the rain forest; the Portuguese took the tree to India, Eastern Africa, and others countries. The cashew tree produces very peculiar apples (a swollen peduncle that gives a sweet flavourful j uice). At the end of this peduncle, the cashew nut grows externally in its own grey coloured kidney shaped hard shell, which is 2.5-4 cm long. This shell (about 0.3 cm thick) has a soft leathery outer skin and a thin hard inner skin. Between these skins is a honeycomb structure containing a liquid called the cashew nut shell liquid. The nuts consist of the kernel (20-25%), the shell liquid (20-25%), and the testa (2%), the rest being the shell. The kernel is presently the more valuable product from the cashew factories: the cashew nut shell liquid is a by-product looked on mainly as a waste. With cashew nuts, it is not possible to use straightforward nut-cracking techniques to recover the kernel and extract the shell liquid, therefore more specialised processes have been introduced. The most popular is the so-called 'hot-bath method'. The principle is to soften the outer shell, by immersion in water at 22-25°C, treatment with steam to open the pores, followed by heating in a bath of hot (180 °C) CNSL itself for 1.5-4 min. (Rajapakse, R.A., J Natl. Sci. Counc. Sri Lanka, 1977, 5, 117-124; Chem. Abstract 89: 195695). Another technique is the 'sun dry/steam/expeller method' which involves sun drying, softening of the whole nuts (by high pressure steam, 2-3 bar) and hammering/cutting the shell with a manual guillotine. The oil is then obtained with an expeller. A range of other techniques are known. Table 1 shows typical compositions of natural CNSL, steam- extracted CNSL and technical CNSL (Shobha S.V., Ravindranath B., J Agric. Food Chem., 1991, 39, 2214-2217; Tyman, J.P.H., Tychopoulos, V., Chan, P., J. Chromatogr., 1984, 303, 137-150; Kubo, I., Komatsu, S., Ochi M., J. Agric. Food Chem., 1986, 34, 970- 973; Shobha, S.V., Krishnaswamy, P.R., Ravindranath, B., J. Agric. Food Chem., 1991, 39, 2295-2297; Skopp,G., Schwenker,G., Plant Med, 1984, 50, 529-533). Natural CNSL is the liquid as it exists in the plant and technical CNSL is the liquid obtained in factories that use the hot-bath oil process of extraction.
Table 1
a) refers to methylcardol and cardol, b) Most of these compounds are reported to be non-volatile, and are assumed to be polymeric. As seen in Table 1 and in the formulae shown below, the main constituents of CNSL are anacardic acid (formula 1), cardanol (formula 2) and cardol (formula 3).
Anacardic acid is a salicylic acid, while cardanol and cardol are substituted phenols. The heat treatment carried out during the processing of cashew nuts to obtain the kernels results in the decarboxylation of the anacardic acid:
m (2)
Anacardic acid Cardanol
In the case of the steam-extracted CNSL, analysis of the solvent extracted shell before and after the industrial process has shown that less 20 % of the original anacardic acid is decarboxylated. The compositions of natural and technical CNSL are known to vary with time and with the country of origin of the plant.
Figure 5 shows a typical proton NMR spectrum for technical CNSL. Referring to Fig. 5, Signals labelled "1" correspond to the aromatic protons of cardanols, and the signal "5" to both cardols and methylcardols, which are minor compounds in the oil. The signals corresponding to the protons of the terminal vinyl groups are "2" and "4". Signal "3" represents the hydrogens of the internal alkenes. Signal "7" corresponds to the benzylic protons of cardanols, and the small shoulder labelled as "8" to the benzylic protons of cardols and methylcardols. The shifts corresponding to the saturated CH groups of the chain for both families of alkenylphenols overlap; signal "6" corresponds to the protons a to two double bonds, "9" to those a to one double bond, "10" to those a to the benzylic protons, "11" to the remaining hydrogen in the carbon chain, and "12" to the terminal methyl groups. The integrals corresponding to the aromatics protons allowed a molar ratio between cardanols and cardols to be calculated. These assignments were supported by HNMR spectra of the separated compounds.
A typical the HNMR of Indian cashew nuts obtained by Petrol soxlhet extraction is shown in Fig. 6. Signals labelled "1", "2" and "3" correspond to the aromatic protons of the anacardic acids, "4" to all cardols protons. The remaining signals are also in the technical CNSL HNMR and correspond to the terminal vinyl groups, the internal alkenes, the benzylic protons, protons a to two double bonds, a to one double bond, a to the benzylic protons, to the remaining hydrogen in the carbon chain, and to the terminal methyl groups.
Because of the different compositions of CNSL, separation techniques of the oil into its constituents reported in the literature refer either to technical CNSL or to the natural oil and are summarised below.
Technical CNSL i) Chemical treatment
For many years, the main use for technical CNSL was as a commercial source of friction dusts for brake-clutch linings. Since all the phenolic components contribute to the final product, no emphasis was placed on separating it into its main components. The main purification was a chemical treatment, being a flocculation with an acid to remove part of the polymeric and other materials (mainly coloured) present in the oil. Different applications (paints, resins and others) were developed for the main component of the oil, cardanol (with some cardol). ii) Distillation
As the flocculation technique was not good enough for specific applications (e.g., specialised resins and dyes), distillation techniques were developed to separate CNSL into its main components. In commerce the distilled fraction is generally called "cardanol" (confusingly, as it contains both cardanols and cardols). Because of their high boiling points and their tendency to co-distil, high temperatures and a high reflux ratio are needed to separate cardanol and cardol. This led to significant polymerisation and consequently to a low yield. Different approaches have been attempted to improve the yield of the distillation, including the use of steam distillation, inert gas with agitation, or an antioxidant, and the use of specialised equipment (a 10 stage rotary still) separated cardanols (99 % purity) in 58% yield (Durrani, A.., Davis, G.L., Sood, S.K., Tychopoulos, V., Tyman, J.P.H., J. Chem. Technol. Biotechnol, 1982, 32, 681-690). One of the approaches was to change the properties during the distillation step by modifying the CNSL by treating with an amine (US 4,392,944), and the resultant amine with formaldehyde in methanol (Tychopoulos, V., PhD thesis, 1989, Brunei University). In this case, the cardol forms a Mannich salt that can be separated from cardanol prior to the distillation. However, none of these methods led to a significant improvement in the yield and/or the possibility of obtaining pure compounds. Part of the cardol remains with the polymeric fraction of the oil as a residue with little commercial value. While the distillate contains both cardanols and cardols, the non-volatile fraction (so-called polymer) of the oil is removed by this process, so it is possible to argue that the main purpose of this distillation is to get rid of it. iii Liquid-liquid extraction with immiscible non-aqueous solvents
Liquid-liquid extractions of phenols from industrial effluents are currently performed on a large scale. In the case of CNSL, this technique uses the selective partitioning of the main constituents of technical and/or natural CNSL between a non-aqueous, non-polar solvent like petrol and an insoluble non-aqueous polar solvent (like ethylene glycol, propanediol, etc.). A fraction of the cardanols remains in the non-polar solvent while the remainder, with all the cardols, migrates to the polar solvent. In the case of natural CNSL, anacardic acid remains in the non-polar layer and cardol migrates to the polar one. One disadvantage of this method is that it doesn't allow the separation of the polymeric fraction from cardanols. It is known that these two constituents (polymer and cardanols) have different properties in various applications (Moreira, L.F.B., Lucas, E.F., Gonzalez, G., J Appl. Polym. Set, 1999, 73, 29-34).
Bruce reported (Bruce, I., PhD thesis, 1992, Brunei Universty) that when technical CNSL was distributed between two non-miscible solvents, petroleum and a diol, some cardanol migrated to the non-polar layer, while the remainder and all cardol remained in the polar phase. A possible explanation is that the two -OH groups of the diols interact preferentially (by hydrogen bonding and dipole interactions) with the two -OH groups of cardols. The main disadvantage of this procedure is that only small amounts of cardanols or anacardic acid are typically recovered in this process. Most of the compounds remain as a mixture with other constituents of the oil. It is not possible to recover the refined oil from the solvents proposed because, as reported previously, some oil constituents are thermo-labile. Separation of the refined oil from the solvents needs therefore to be performed by dilution with water and re-extraction, with consequential losses and negative environmental impact due to contamination of the residual water. iv) Solvent extraction using water-methanol-ammonia-hexane systems
A recent study, (Paramashivappa, R., Kumar, P., P., Vithayathil, P.J., Srinivasa, R.A., JAgricFood Chem., 2001, 49, 2548-2551) reported a separation of CNSL (with 63.% anacardic acids, 11 % cardanols, 22 % cardols) in a two-step procedure. Paramashivappa, R., Kumar, P.P., Vithayathil, P.J., Srinivasa, R.A., JAgricFood Chem., 2001, 49, 2548- 2551 Anacardic acids separation was performed on the basis of the non-solubility of its calcium salt (using methanol as solvent). Separation of cardanols from cardols was then performed using the partition between a non-polar and a polar layer. However as the solvent system chosen (petrol - methanol with ammonia (25%)) has very low capacity to remove cardanols (lower than petrol-butanediol), it was modified with ethyl acetate. Ethyl acetate is a non-selective modifier (some cardols migrate to the non-polar layer); selective modifiers must be immiscible in the non-polar phase. To eliminate these cardols from the petrol layer, the literature procedure washed this layer with dilute sodium hydroxide. This led to losses in the aqueous layer. To recover the cardols from the polar layer a new approach was to extract it from the methanol-ammonia layer with ethyl acetate. It was claimed that it was possible to obtain cardols (100 % purity by HPLC), in high yield. This later concept was therefore tested by dissolving cardols in methanolic ammonia and adding in a separating funnel ethyl acetate in amounts indicated in the paper. This gave an homogeneous solution which separated only on adding 4 times more ethyl acetate. Recovery of cardols from the ethyl acetate was only 45 %. The same group published a modified version of this procedure, (Kumar PP, Paramashivappa R, Vithayathil PJ, et al., J Agric. And Food Chem., 2002, 50 (16): 4705-4708) using just petrol-ammonia-methanol to separate technical CNSL and claimed to obtain cardanols (100 % pure by HPLC) and cardols (100 % pure by HPLC) with 100 % recovery. With both CNSL Bras, and CNSL VMSRF these results were irreproducible, as it was only possible to obtain pure cardanols in low yields, and a mixture of cardanols-cardol, as in the petrol-diol and petrol-amine experiments reported in the experiments (Kumar, P,P, Paramashivappa, R., Vithayathil, P.J., Subba R. P.V., Srinivasa, R.A., J.Agric.Food Chem., 2002, 50, 4705-4708). v) Supercritical extraction with carbon dioxide and propanol
Cardanols and cardols have been extracted from CNSL by supercritical extraction with carbon dioxide using propanol as co-solvent. Due to the high pressure involved this process is not inexpensive, although in some circumstances the elevated cost may be justified on the grounds of the high potential value of cardols (JP 0500979). vi) Fractional crystallization
Separation of CNSL (containing anacardic acids 69.5%, cardols 21.2% and cardanols 4.6 %) was reported to be achieved by fractional crystallization in pentane. The crystals collected at temperature of -65 °C gave anacardic acids (purity 99.7%), while the fraction that crystallized at -180 °C gave cardols, (purity 90.5 %) (JP 10182549; Chem. Abst. 129:108903 and JP 10259150; Chem, Abst, 129:260226).
Natural CNSL i) Extraction of anacardic acid by treatment of natural CNSL with a base
The separation of cardols from natural CNSL has been achieved by removal of the anacardic acid with a methanolic solution of lead hydroxide (Backer, HJ, Haack, NH, Rec. Trav. Chim, 1941, 60, 656-677) or calcium hydroxide (US 2431127). Separation of the salts by filtration and subsequent treatment of the solid with mineral acids regenerates anacardic acid in high purity. The main problem of this approach is that a huge amount of salt is generated. if) Isolation of cardols from natural CNSL by acid base treatment and crystallization
The separation of cardols from natural CNSL has been achieved by removal of the anacardic acid with a methanolic solution of lead hydroxide, of calcium hydroxide, and recently using resins followed by fractional crystallisation. In the latter case, after removing the anacardic acid with a resin, cardols were re-crystallised by cooling to a temperature between -25 °C and -195 °C (JP 10259150). An unverified report also suggests that cardols could be removed from natural CNSL by simply leaching the oil with a solution of sodium hydroxide (US 2,230, 995). iii Anacardic acids by petrol-diol liquid extraction
JP 8217720 uses liquid-liquid extraction with a petrol-diol solvent system to separate anacardic acid from natural CNSL. Reported anacardic acid recovery varies between 8- 14%. iv) Use of supercritical extraction
Recently a supercritical extraction process has been optimized, but high recovery yields (94%) still require high pressure (15-30 MPa), implying that this process is relatively expensive (Smith Jr. R.L., Malaluan R.M., Setianto W.B., Inomata PL, Arai K., Bioresource Technology, 2003, 88, 1 , 1-7).
Thus, the presently known techniques for the fractionation of CNSL have associated drawbacks. These techniques may be expensive (e.g. supercritical separation or fractional crystallisation), they may lead to production of unwanted waste (e.g. use of base calcium hydroxide) or they may provide a relatively inefficient means for separation of the CNSL constituents (e.g. distillation techniques). In the case of liquid-liquid extraction processes, the use of the techniques previously proposed in the art require a very high number of separation stages (perhaps greater than 20), whatever the reflux ratio. This could not be used on an industrial scale. It has been suggested that a maximum of seven re-extractions is economically feasible (Hanson, C. "Recent advance in liquid-liquid extraction", 1971, Pergamon Press).
The present invention has been made from a consideration of these drawbacks, and provides a technically and economically useful solvent-solvent extraction method for the separation of CNSL.
According to a first aspect of the present invention, there is provided a method for the fractionation of cashew nut shell liquid, comprising solvent-solvent extraction using a polar solvent component and a non-polar, non-acidic, non-basic solvent component; wherein the polar solvent component is a mixture comprising:
i) a first solvent comprising a fluorinated solvent; and
ii) a second solvent comprising a solvent satisfying the following parameters:
a) Hildebrand parameter greater than 10 (kcal dm ) ' and
b) dipolarity/polarizability (π), hydrogen bond acidity (a), and hydrogen bond basicity (β) having the following relationship:
α/(α + β + π) > 0.5;
β/(α + β + π) < 0.8; and
π /(α + β + π) > 0.3.
This aspect of the present invention provides a solvent-solvent extraction method by which anacardic acid and cardol can be separated and obtained from natural CNSL, and cardanol and cardol can be separated from technical CNSL. In contrast, the prior art solvent-solvent procedures either imply too great a number of extraction-re-extractions, or were not reproducible. It has now been found that solvent-solvent extraction using the mixture of solvents in accordance with this aspect of the present invention provides a feasible separation of CNSL, with relatively easy, relatively low-cost solvent recovery.
Thus, this aspect of the present invention may also be considered a method of production of anacardic acid and/or cardol from CNSL, or a method of production of cardanol and/or cardol from technical CNSL. The components may be obtained in excellent purity, and have a number of uses, including use as intermediates in synthetic processes for making complex structures based on anacardic acid or cardols skeletons.
In the making of the invention, the following important solvent properties were considered: the selectivity (measured as a ratio between the concentration of the two compounds to be separated in the extract-rich phase); and
the capacity (measured as a ratio of the solute concentration between the raffmate and the extract phase);
It has been found here that fluorinated solvents provide high selectivity to cardol, but very low capacity. The capacity of these fluorinated solvents can be increased by the addition of the second solvent in the mixture. Thus, the solvent mixture of the first and second solvents provides a polar solvent component for use in conjunction with a non- polar solvent component in the solvent-solvent extraction procedure. The non-polar solvent component typically comprises a non-polar, non-acidic, non basic solvent.
The second solvent is selected on the basis of its Hildebrand parameter (δκ) being greater than 10 (kcal dm -3 ) 0,5 . A comprehensive collection of Hildebrand parameters may be obtained from the literature (Kamlet M. J., Carr P. W., Taft R.W., Abraham M. H., Journal of American Chemical Society, 1981, 103, 6062-6066; Par J. H., Lee Y. K., Cha J. S., Kim S. K., Lee Y. R., Lee C.-S., Carr P. W., Microchemical Journal, 2005, 80, 183- 188; Barton A. F. M., Chemical Reviews, 1975, 75, 731). Alternatively, Hildebrand parameters may be calculated using the equation bn = (-E/V)° '5 where—E is the molal heat of vaporization to a gas at zero pressure and Vis the molal volume.
The dipolarity/polarizability (π) measures the ability of the solvent to stabilize a charge or a dipole by virtue of its dielectric effect. Values of (π) for solvents with a single dominant moment dipole have been shown to be proportional to dielectric constant and the refractive index.
Hydrogen bond acidity (a) describes the ability of the solvent to donate a proton to solute. Hydrogen bond basicity (β) provides a measure of the solvent's ability to accept a proton. These last two terms were historically derived from spectral shifts (for instance, basicity has been calculated with 19 F NMR shifts of 5-fluoroindole complexes with bases, or from the frequency of the electronic transition of dissolved 4-nitrophenol and 4- nitroanisole), but have been also derived by other methods, e.g., the acidity of the solvent has been related with LUMO-HOMO energies, or with the electrostatic potential at the donor hydrogen nuclear position. Procedures to calculate α, β and π, and the corresponding values for most common solvents are reported in the literature (Kamlet, MJ, Abboud, JL, Abraham, MH, Taft, RW, J Org. Chem., 1983, 48, 2877-2887; Snyder L. R., Carr P. W., Rutan S. C, Journal of Chromatography A, 1993, 656, 537-547; and Y. Marcus Chem. Soc. Rev. 22 (1993), p. 409).
A second aspect of the present invention provides a solvent mixture for use in the fractionation of cashew nut shell liquid by solvent-solvent extraction, wherein the solvent mixture comprises:
i) a first solvent comprising a fluorinated solvent; and
ii) a second solvent comprising a solvent satisfying the following parameters:
a) Hiidebrand parameter greater than 10 (kcal dm ) ' ; and
b) dipolarity/polarizability (π), hydrogen bond acidity (a), and hydrogen bond basicity (β) having the following relationship:
α/(α + β + π) > 0.5;
p/(a + p + 7T) < 0.8; and
π /(α + β + π) > 0.3.
A third aspect of the present invention provides the use of a solvent mixture in the fractionation of cashew nut shell liquid by solvent-solvent extraction, wherein the solvent mixture comprises:
i) a first solvent comprising a fluorinated solvent;
iii) a second solvent comprising a solvent satisfying the following parameters: a) Hiidebrand parameter greater than 10 (kcal dm -3 ) 0'5 ; and
b) dipolarity/polarizability (π), hydrogen bond acidity (a), and hydrogen bond basicity (β) having the following relationship:
α/(α + β + π) > 0.5;
β/(α + β + π) < 0.8; and
π /(α + β + π) > 0.3.
The solvent mixture of the first and second solvents provides a polar solvent component for use in conjunction with a non-polar solvent component in the solvent- solvent extraction procedure. The non-polar solvent component typically comprises a non- polar, non-acidic, non basic solvent. With regard to the first solvent, this comprises a fluorinated solvent. Non-limiting examples of the fluorinated solvent include fluoroalcohols, fluoroamines and nitrofluorinated solvents, including, e.g., trifluoroethanol, fluorophenols, fluroxene, enflurane, isoflurane, methoxyflurane or hexafluoro-2-propanol, or any combination thereof. However, it will be appreciated that other suitable fluorinated solvents may be employed. In preferred embodiments, the first solvent comprises trifluoroethanol (TFE). It has been found that TFE has high selectivity but low capacity, the capacity of the solvent mixture being improved by the second solvent.
With regard to the second solvent, this comprises a solvent with a Hildebrand parameter greater than 10 (kcal dm -3 ) 0'5 . This parameter is a measure of the energy needed to separate two molecules of solvent. Solvents with such a low parameter solubilize the other solvents present in the mixture and both anacardic acid and cardols. The values of the dipolarity/polarizability (π), hydrogen bond acidity (a) and hydrogen bond basicity (β) are limited by the following mathematical relations: α/(α+β+π) > 0.5; β/(α+β+π) < 0.8; and π/(α+β+π) > 0.3. These parameters can be described by the correspondent area in the tertiary diagram shown in the accompanying Fig. 1, and thus a range of suitable commercially available solvents can be identified that may be used to provide separation with high selectivity. By way of illustration only, Fig. 1 includes a number of non-limiting examples of suitable solvents.
Preferred solvents include acetonitrile and nitromethane.
The two-component polar solvent system selectively solubilises cardol. The non- polar solvent preferentially solubilises anacardic acid and cardanol. Thus, in the fractionation of cardol, the non-polar solvent is not a necessary component of the mixture as the cardol will partition in the two-solvent system, itself immiscible with the remaining anacardic acid/cardanol milieu. However, it may be preferred in an industrial installation to use a non-polar solvent to reduce the viscosity of the non-polar stream and increase the rate of phase separations.
The cashew nut shell liquid (CNSL) may comprise natural CNSL or technical CNSL, or any other corresponding oil extracted from the cashew shell by a range of methods (such as steam extraction, activated steam extraction, and other methods known in the art). The mixture of the first and second solvents may of course contain additional components useful in separation procedures, examples of which will be apparent to the skilled person, such as an anti-foam agents, rheological modifiers, etc.
Usefully, aspects of the present invention provide methods for obtaining a range of anacardic acids or cardol derivatives by selectively cleaving natural anacardic acids or cardols mixture at the C-8 double bond.
With regard to the solvent-solvent extraction procedure, any suitable method may be employed, as will be understood by the skilled person. The methods include co-current, counter-current, and one-step extractions. Counter-current extraction methods are preferred. The ratio of feed/solvent may vary, e.g. between around 0, 1 to around 50, and the temperature of extraction may vary, e.g. between around -25°C to around 70°C.
In the solvent-solvent extraction, the non-polar solvent component, typically a non- polar, non-acidic, non-basic solvent, is used in conjunction with the polar solvent mixture according to the invention. The non-polar solvent is not critical to the invention, however, and in certain aspects and embodiments the polar solvent mixture may be used in the absence of a non-polar solvent. For instance, the mixture of the first and second polar solvents may be used to selectively extract cardol from CNSL in the absence of a non- polar solvent. However, the non-polar solvent may be useful in industrial processes to reduce the viscosity of the CNSL mixture in the extraction column. The non-polar solvent may comprise any suitable solvent or mixture of solvents, including, e.g., aliphatic solvents, pentane, hexane, heptane, octane or other alkanes, isoalkanes, or a mixture of a range of chemical entities, such as petroleum ether.
It has been found that impurities which may be present may flocculate when the solvent- solvent extraction is carried out. The impurities may be removed by filtration.
Thus, one embodiment of the present invention provides a method of producing low viscosity CNSL from CNSL by solvent-solvent extraction to flocculate any impurities which may be present in the CNSL, and removing the flocculated impurities. Typically, the CNSL is technical CNSL.
Technical CNSL composition varies as a function of the time and temperature used in processing; long reaction times and high temperature typically give rise to unwanted products, which have been described as polymeric fractions (Bruce, IE, Long, PBP, Tyman, JPH, J Liq. Chrom., 1990, 13, 10, 2103-2111). In the previously published studies, samples from Mozambique and Brazil provided high concentration of such unwanted products, while samples from India provided no such fractions. The impurities may then be removed by filtration or any other liquid-solid method of separation (by centrifugation, use of hydrocyclone, etc.).
In this embodiment of the present invention, any impurities in the CNSL may be flocculated using the first solvent as hereinbefore described or the second solvent as hereinbefore described, or any mixture of the first and second solvents. Using this embodiment of the present invention, it is now possible to produce low viscosity CNSL which fulfills Indian Standard 840-1986 specifications for technical CNSL, without distillation, but by solvent-solvent extraction. Preferably, the sovent-solvent extraction is carried out using a mixture of nitromethane or acetonitrile with petrol. The solvents may be removed by, e.g., vacuum distillation.
Examples of typical processes for solvent-solvent extraction according to aspect of the present invention are shown in Fig. 2 (Scheme 1) and Fig. 3 (Scheme 2) below. Scheme 1 relates to the separation of cardol and cardanol from a technical CNSL with high concentration of degradation products, whereas Scheme 2 relates to the separation of anacardic acid and cardol from natural CNSL. It is of course to be understood that these schemes are provided by way of example only, and variations which will be apparent to the skilled person, including the use of further solvents, introducing the feed at other positions in the column, etc.
The standard approach to determine industrial feasibility of an extraction process is to determine as a function of equilibrium data and rate of feed/solvent the number of theoretical extraction column plates. This parameter is then used in empirical correlations provided by equipment manufacturers to estimate the real number of plates and therefore the dimensions of the extraction column. The technical feasibility may then be estimated, so, for instance, if the counter-current column is 50 m high it is not technically feasible.
The present invention provides a technically feasible system for use in fractionation of CNSL. Experimental data show that a solvent mixture according to an aspect of the present invention may be used in a counter-current system to separate cardanols from cardols (obtaining cardanols pure, and cardols 87 %). As an example, a unit providing 3.75 kg/h cardols operating at a ratio of solvents petrol:TFE:ACN (10:5:0.25) would need to be 1.72 m high, and 0.27 m in diameter. An increase of capacity to 20 kg/h would correspond to a column of 2.4 m height and 0.6 m in diameter. These separation units are obviously technically feasible. To separate technical CNSL in cardanol and cardol an extraction process using petrol-TFE system, using the procedure indicated previously would correspond to two columns, one of at least 18 m to obtain a cardol rich extract and one of 9 m to obtain cardols 100 % pure. There is no disclosure in the prior art of using a petrol-TFE system to separate CNSL constituents. The prior art (e.g. JP8217720 and others cited above) proposed using the petrol-ethylene glycol system or other systems with similar selectivity. In this case, two columns of 50 m would be required to obtain pure cardanol and cardol 90%. Because of such inefficiencies, such systems are not presently used.
In Scheme 1, technical CNSL is pumped through a mixture vessel where it is mixed with a mixture of first and second solvents as hereinbefore described. This affords flocculation of a "gummy" phase reported by some authors to be a polymeric fraction. The CNSL-solvent mixture is then pumped to the counter-current extraction column where it contacts with an aliphatic solvent introduced at the base of the column. The polar stream rich in cardol is separated at the base of the column while the non-polar stream rich in cardanol is removed at the top of the column.
In Scheme 2 natural CNSL (mixed with the aliphatic solvent) is pumped to the extraction column.
Aspects of the present invention will now be illustrated in the following non- limiting examples.
Examples
Characterisation of CNSL
A number of different samples of CNSL were used in experimental methods.
Technical CNSL
a) from Brazil, labelled as CNSL Bras;
b) from Mozambique, Machava Factory, labelled as CNSL Moz;
c) from India, Ajay Metachem (this sample has been refluxed with sulphuric acid/hydrochloric acid by the manufacturer); d) from India, Villa Maya Scientific Research Foundation; and
e) one sample, from unidentified origin, supplied by Cardolite.
General characterisation of unpurified technical CNSL
CNSL Bras is a black viscous oil which showed (see 1 HNMR in Figure 4), * H (CDC1 3 ), 7.18-7.09 (m, 0.95 H), 6.81-6.63 (m, 2.85 H), 6.33-6.21 (bs, 0.024 H), 5.92-5.78 (ddt, 0.3 H), 5.52-5.35 (m, 2.7 H), 5.13-4.97 (m, 0.6 H), 2.87-2.75 (m, 2.6 H),2.68-2.56 (t, 1.9 H; J= 7.4 Hz), 2.56-2.40 (bs, 0.024 H), 2.17-1.93 (m, 3.8 H), 1.71-1.51 (bs, 2.6 H),1.50-1.20 (m, 14 H), 0.98-0.95 (m,2.5 H), < max 3400, 3010, 2925, 2856, 1487 cm "1 . HPLC analysis was carried out by taking an aliquot (25 mg) and adding 4-hexylresorcinol (5 mg) as internal standard. The mixture was dissolved in THF and filtered through a nylon Aldrich cartridge. The cartridge was eluted with further THF (3 x 3 ml), and the combined eluant was made up to 50 ml into a volumetric flask. TLC analysis of the extract of the cartridge with ether showed that no cardanol or cardol was retained. The solvent (acetonitrile- water-acetic acid (78:20:5) for 30 min followed by gradient elution with THF-water over an additional 30 min.) was pumped at 1 ml/min. The sample was introduced automatically, allowing 20 μΐ analyte to be injected into a guard column before passing through a Phenomenex Luna HPLC column, 4.6 x 150 mm, packed with 5 μ PhenylHexyl silica. The detector was set at 280 nm. Pure constituents of cardanols and cardols, and their hydrogenated congeners were obtained using the method described below. The relative response factor of cardanols to cardol was 1.09. For different CNSL samples the areas from the chromatograms are presented in Table 2:
Table 2
The cardol/methylcardol concentration in technical CNSL, obtained by NMR, correlates with the one obtained by HPLC, while the cardanol concentration obtained by NMR, is slightly higher. However, the fact that concentration of cardanols plus "others" obtained by HPLC correlates with that deduced by NMR suggests that "others" detected by HPLC have aromatic protons similar to those in cardanols. Samples without "others" (from AJAY, VMSRF) were significantly thinner than the others (CNSL Moz, and CNSL Bras and in a smaller measure CNSL Cardolite).
Natural CNSL
Natural CNSL was obtained by solvent extraction from shells of Indian and Tanzanian cashew nuts .
Extraction of natural CNSL i) Extraction by percolation
Cashew nuts from India (0.9 kg) were stored overnight in a freezer to make the shell brittle. The nuts were then bisected by light hammering with a knife along the junction of the halves of the shell. The internal kernel testa lining was then separated, and parts of the testa still in the shell were removed by knife/ and brushing. Cleaned shell (710 g) was powdered in a home coffee mill, and the ground shell was extracted by percolation over a column filled with the powdered shells, using successively dichloromethane (3 x 1 1), ethyl acetate (3 x 1 1), and methanol (3 1 1). The combined extracts were filtered on a celite/silicagel pad and evaporated to constant weight, under vacuum, at room temperature giving a reddish oil (174 g).
8 max at 308 nm,s raax 3400, 3010, 2925, 2856, 1487, 1262 cm "1
MS (DI), M 328, 346, 396 (minor peak), HNMR spectra.
ii) Extractions of ground shells with soxlhet, and by churning
Samples of cashew nut ground shell (3 x 10 g) obtained by the procedure described in the i) above, were extracted separately with 3 solvents (petrol, acetone, and methanol) using a soxhlet for 6 h or by churning the ground shells for 24 h, in the solvents indicated. Yields and ratio cardol/anacardic acid are provided Table 3 below.
Table 3
Reference experiments
A number of different experiments were carried out using known separation techniques, by way of reference.
Petrol-glycol partition and other petrol-diol partitions
Technical CNSL (1000 mg) was dissolved in petrol (10 ml) to which was added diethylene glycol (10 ml). After shaking, the petrol and the diol layers were allowed to separate. Removal of the solvent from the non-polar layer gave pure ( 1 HNMR identical to that above) cardanol (65 mg). The glycol layer was diluted with water (2 10 ml) and re- extracted with ethyl acetate (3 x 10 ml) to give, after drying over magnesium sulfate, a mixture of cardanol-cardol (812 mg) with 'HNMR similar to that of CNSL. The same procedure was repeated using other diols (1,3 -propanediol, 1,2-butanediol, 1,4-butanediol and 1,5-pentanediol) instead of glycol. The results of the petrol-diol extractions are presented in Table 4.
Table 4
a) the NM was similar to that of the initial CNSL
Continuous extraction petrol-diol system
By shaking and decanting, in a separating funnel, CNSL (10.00 g), petrol (100 ml) and 1,4- butanediol (100 ml), the top layer afforded cardanol (0.65 g), while the bottom polar layer was submitted to continuous extraction in a standard laboratory apparatus. The polar phase was thus introduced into the top reservoir, with petrol (100 ml) in the lower flask. The petrol was then evaporated, and condensed (at a rate of ca. 1 drop/sec.) to flow through the polar phase. The top of the condenser was closed with a rubber septum, topped with an argon filled balloon. The petroleum flask was changed each 4 h, and the solvent was removed in vacuo to allow isolation and characterisation of the extract. Pure cardanol (3.23 g) was obtained after 60 h. The polar layer was dissolved in water (2 x 100 ml), and re-extracted with ethyl acetate (3 x 100 ml) to give, after drying on magnesium sulfate, a mixture of cardanol-cardol (5.12 g) (ca.. 10/1 by NMR). The procedure was repeated with using 1,5-pentanediol instead of 1,4-butanediol. The top layer from the separating funnel afforded cardanol (0.79 g), while the continuous extraction after 60 h afforded more cardanol (3.21 g) and a mixture of cardanol-cardol (4.7 g) (ca. 10/1 by NMR).
Petrol-amino derivatives partition
Technical CNSL (1000 mg) was dissolved in petrol (10 ml) to which was added diethanolamine (10 ml). After shaking, the petrol and the amine layers were allowed to separate. Removal of the solvent from the non-polar layer gave pure ('HNMR identical to that above) cardanol (92 mg). The polar layer was diluted with water (2 x 10 ml) acidified with aqueous HC1 (10 %) until pH = 1 and re-extracted with ethyl acetate (3 x 10 ml) to give, after drying on magnesium sulfate, a mixture of cardanol-cardol (580 mg) with 1 HNMR similar to that of CNSL. The procedure was repeated using monoethanolamine, diethylenetriamine, diethylenetetramine, or t-butylamine. The yields obtained are shown in Table 5 :
Table 5
a) some traces of cardols b) HNMR very similar with that of CNSL
Additional technical CNSL extractions
i) Technical CNSL (1000 mg) in methanol (6.6 ml) was successively added water (0.32 ml), and ammonia (25 %, 6.6 ml). The mixture was stirred for 30 minutes and extracted with hexane/ethyl acetate (98:2) (3 x 6 ml). The combined organic layer was washed with NaOH solution (2.5 %, 6 ml), followed by HC1 solution (5 %, 3 ml). The organic layer was dried over magnesium sulphate and concentrated to give a pale brown oil characterized by HNMR spectrum. The methanolic ammonia solution was then extracted with ethyl acetate-hexane (80:20) (6 ml). The organic layer was washed with HC1 solution (5%, 3 ml) followed by distilled water (3 ml). The organic layer was dried over magnesium sulphate, and concentrated to give a pale brown oil characterized by HNMR spectrum. Results are shown in Table 6:
Table 6
a) after NaOH, HC1 treatment b) after HC1, distilled water treatment ii) Technical CNSL (1000 mg) was dissolved in methanol (32 ml) and ammonium hydroxide (25 %, 20 ml) and stirred for 15 minutes. The solution was extracted with petrol (4x 20 ml). The organic layer was concentrated to get cardanols (pure by HNMR, 62 mg). The methanolic ammonia solution was extracted with ethyl acetate. The resulting organic layer was concentrated under vacuum to get a mixture of cardanols-cardols very similar to the starting material ( 534 mg) by 1 HNMR. iii) Cardols (100 mg) were dissolved in methanol (3 ml) and ammonium hydroxide (2 ml). This solution was extracted with ethyl acetate (4x 2ml), to afford, after removal of the organic solvent, cardol, pure by HNMR, (45 mg).
Other reference examples include tests carried out in the development of the invention. Non-diol, non-amino solvent partition
Technical CNSL (1000 mg) was dissolved in petrol (10 ml) to which was added acetonitrile (10 ml). After shaking, the layers were allowed to separate. Both solvents were removed in vacuo. The non-polar layer afforded cardanol (with ! HNMR identical to that above) (193 mg), while the polar layer afforded a cardanol-cardol mixture (640 mg, ratio 10:1, by 1HNMR). A black resinous material (163 mg) flocculated in the separating funnel (recovered by washing the glassware with dichloromethane) with 1 HNMR identical to that of CNSL, but broader IR similar to that of CNSL though the relative intensity of the peaks at 988, 945, and 910 cm "1 was smaller. The MS-DI spectrum was similar to that of cardanol, but with a small additional peak at m/z 352. This procedure was repeated using trifluoroethanol. The results are indicated in Table 7.
Table 7
Cardanols with traces of cardols by NMR ' values were similar to CNSL c ' Pure by NMR
Back extraction
TFE back extraction
Technical CNSL (1000 mg) dissolved in heptane (1ml) was extracted with TFE (1 ml x 40). Removal of the heptane gave cardanol (752 mg), while the combined TFE layers gave, after removal of the solvent, a cardanol and cardol mixture rich in cardols (0.13 g). This mixture was redissolved in TFE and after re-extraction with heptane (1 ml x 20) gave cardol with TFE (0.034 g, ca. 83 % solvent by 1HNMR). Petrol-acetonitrile back extraction
Technical CNSL (10.00 g) was dissolved in a mixture of petrol-acetonitrile (1 :1), (200 ml). Separation of the two layers, and removal of the solvents under vacuum, gave cardanols (1.95 g) from the non-polar layer, a mixture of cardols-cardanols (5.90 g) (cardanols 91%) from the polar layer, and a sticky material (2.00 g) that flocculated in the flask. The acetonitrile layer was redissolved in ACN (100 ml) and re-extracted with petrol (100 ml). This operation was repeated four times. The weights, and purity assessed by HPLC assay are indicated in Table 8.
Table 8
n.a.: no available data
Continuous extraction
Continuous extraction with P-TFE
Technical CNSL (1.00 g) in petrol (10 ml) was introduced was into the top reservoir, while TFE (100 ml) was put in the lower flask. The TFE was then refluxed, and condensed (at a rate of approx. 1 drop/sec.) to flow through the petroleum phase. The top of the condenser was closed with a rubber septum, topped with a argon filled balloon. After 3 h, a two- phase product appeared in the TFE receptor. TLC showed that both phases contained cardanol and cardol and the experiment was stopped. Continuous extraction with petrol-acetonitrile system
Technical CNSL (20.00 g) dissolved in a mixture of petrol-ACN (1 :1), (200 ml), gave cardanols (5.53 g) after separation of the petrol layer, an enriched mixture of cardols (8.3 g) after separation of the acetonitrile layer and a sticky material (5.76 g) that flocculated in the flask. The acetonitrile layer was redissolved in ACN (100 ml), introduced into a continuous extraction device and re-extracted with petrol over a period of 36 h. Hourly samples of the petroleum layer, and the final ACN layer were analysed 1 HNMR and results are shown in Table 9. The viscosity of the oil obtained after evaporating the correspondent ACN layer was very high.
Table 9
a) The mass of all of these fraction is 14.30 g, remaining material accounted for the sticky flocculate (5.76 g), and losses (0.10 g). Losses were estimated on the basis of the mass balance.
Petrol-Acetonitrile solvent extraction of natural CNSL
Natural CNSL (10.00 g) was injected to a separating funnel containing petrol (10 ml) and ACN (10 ml). Immediately after shaking, two liquid phases separated. After evaporation of the solvents, the petroleum layer gave a brown oil (1.93 g, 19 %) (anacardic acid by NMR), while the ACN layer gave also a brown oil (8.02 g, 80 %) (mixture of anacardic acid/cardol, ratio by NMR: 2.1 (mol/mol )). An aliquot of the brown oil from the petroleum layer was then dissolved in diethylether (2 ml) treated with diazomethane (2 ml) to gave a mixture of methylated anacar die acid (1H CDC1 3 ), 7.37-7.35 (t, J = 8 Hz, 1H), 6.87-6.81 (dd, J =8.1 Hz, 1H), 6.75-6.68 (dd, J= 8.1, 1H), 5.92-5.78 (ddt), 5.42-5.35 (m, 2H), 5.13-4.97 (dd), 3.98 (s), 3.3.94 (s), 3.80 (s), 3. 3.12-2.87(t, J = 7.5 Hz, 2H), 2.90= 2.70 (bs, 2H), 2.01 (bs, 2H) 1.59-1.20 (bs, 27H)., 0.98 (t, J =7.5 Hz, 3H).
Test examples
The following test examples are provided by way of illustration only of aspects of the present invention.
TFE-co solvent, multiple extraction of the petroleum layer to afford pure cardanol a) TFE- acetonitrile (10: 1, v/v)
Technical CNSL (1.00 g) in petrol (10 ml) was extracted with TFE-acetonitrile (3 x (10 ml-1 ml)). The non-polar layer afforded cardanols (0.62 g) while the combined polar layers afforded, after removal of the solvent, a mixture of cardanols/cardols (1 :1, by NMR) (0.28 g). A resinous black solid (0.08 g) with a broad NMR spectrum similar to that of crude CNSL, was recovered after washing the separating funnel with THF. b TFE- nitromethane (10: 1, v/v)
The procedure used in a) was repeated using nitromethane instead of acetonitrile. The non-polar layer afforded cardanols (0.58 g), while the polar layer afforded a mixture of cardanol-cardol (1.1 : 1, by NMR, 0.22 g). A resinous black solid (0.10 g) was obtained upon washing glassware with THF. The cardanols were pale-yellow coloured.
Cardol recovery
Continuous extraction with P-TFE-ACN system
Technical CNSL (4.00 g) dissolved in petrol-TFE-ACN (10:10:0.5) (82 ml), gave after separation of the layers, cardanol (1.98 g) from the petroleum layer, a cardol-rich fraction (0.97 g) from the polar layer, and a sticky material together with some solvent (1.52 g) that flocculated on the flask. The fraction from the polar layer was re-dissolved in TFE-ACN (10:0.5) (42 ml), introduced into a continuous extraction device and re-extracted with petrol for 12 h. Hourly samples of the petroleum layer, and the final TFE-ACN layer, were analysed and the results are shown in Table 10. In the petrol-TFE-ACN continuous extraction of CNSL, the ratio of cardols/cardanols obtained in the final polar layer, accessed by HPLC was over 9/1.
Table 10
a) The ratio of cardol-cardanol and the concentration of extract in the TFE layer were constant for the following 2 h and then fell. The reasons for this are unclear.
Multistep back extraction with petrol-TFE-ACN system
Technical CNSL (1000 mg) was dissolved in petrol-TFE-ACN (10:10:0.5, 20.5 ml). Separation of the petrol layer, and evaporation of the solvent gave cardanols (570 mg), while the polar layer gave, after evaporation of the solvent, a mixture of cardols-cardanols (190 mg). A sticky material (300 mg with some solvent) that flocculated on the flask was recovered by washing the glassware with dichloromethane. The fraction from the polar layer was re-dissolved in TFE-ACN ((10:0.5), 10.5 ml) and re-extracted with petrol (10 ml). This operation was repeated four times and the petrol layers were recombined for analysis. The yields and purity are indicated Table 11 : Table 11
Reproducibility studies
Samples of different technical CNSLs (see Table 12 for details) (1.00 g) were each dissolved in a mixture of petrol-TFE- ACN (10:10:0.5, 20.5 ml). Separation of the petrol layer, and evaporation of the solvent gave cardanol with traces of cardols (amount indicated in Table 12), while the polar layer gave, after evaporation of the solvent, a mixture of cardols-cardanols (amount and ratio of cardanol/cardol indicated in Table 12). When a sticky material flocculated on the flask, it was recovered by washing with dichloromethane, and the weight was recorded.
Table 12
Equilibrium data
CNSL Bras (9100 mg) was partitioned in a two-phase system (petrol (100 ml), TFE (100 ml) and ACN (5 ml)). The petrol layer gave, after removing the solvent, an oil fraction (5621 mg), which was removed, as well as the flocculated solid (2010 mg) (with traces of solvent). The TFE-ACN layer was also evaporated to give an oil (1560 mg). An aliquot of the polar layer was removed for HPLC characterization, and the remainder was dissolved in TFE-ACN. This layer was re-extracted with same volume of petrol, and after removing the solvents, both fractions were weighed. HPLC analysis was performed using the same methodology for technical CNSL analysis previously described.
The results are presented in Table 13. Table 13
a)_The area of cardols is area of cardols+ methylcardols
Natural CNSL separation
Optimal ratio using petrol-TFE-ACN
Natural CNSL was injected into a separating funnel containing different amounts of petrol, ACN, and TFE, as indicated in Table 14. After separation of the phases, both layers were evaporated under vacuum, and analysed by NMR. Data obtained are shown Table 14:
Table 14
a) no available data.
Multistep extraction of natural CNSL using petrol-TFE-ACN
Natural CNSL (860 mg) was injected into a separating funnel containing petrol (10 ml), TFE (10 ml) and ACN (0.5 ml), and was separated into two layers ("extraction 1"). The polar layer, corresponding to the TFE-ACN solvents, was re-extracted with petrol (4 x 10 ml, "extractions 2", "3", "4" and "5"). Yields and NMR ratios are indicated in Table 15: Table 15
a) no data
b) 100% cardols by NMR and HPLC
Back extraction of the petroleum layer
The petroleum layer from the previous experiment (corresponding to line 1 from Table 12) (500 mg) was extracted with TFE- ACN (5%) (3 x 10 ml) to give, in the petrol layer, anacardic acid (256 mg) with no cardols.
Equilibrium data for the partition of natural CNSL with P-TFE-ACN (5%)
a) Natural CNSL (8750 mg), was partitioned in a two-phase system (petrol (100 ml), TFE (100 ml) and ACN (5 ml)), to afford a petroleum layer (7030 mg) and a TFE- ACN layer (1681 mg). An aliquot of the polar layer was removed for 1 HNMR, and HPLC (see Table 13). HPLC analysis was performed using the same methodology as for natural CNSL analysis hereinbefore described.
b) The remainder was dissolved in TFE (100 ml) and ACN (5 ml). This layer was re-extracted with petrol (100 ml). After removing the solvents, both fractions were weighed and aliquots collected for ! HNMR, and HPLC characterization.
c) The polar layer was then re-dissolved in TFE (100 ml) and ACN (5 ml), and the procedure described in b) was repeated more 3 times.
The results are presented in Table 16. Table 16
a) cardols + methylcardols
b) too diluted HPLC samples
c) sample too dilute and gave only one peak for anacardic acids by HPLC
New procedure to obtain Technical CNSL
Treatment of cardanols with CHjNO?
Cardanols (10 g) obtained from previous CNSL-acetonitrile-petrol (1 : 10:10) partition, were dissolved in petrol (20 ml) and washed with (30 x 5) ml nitromethane, and provided after the evaporation of solvents, clear brown-reddish cardanols (6900 mg) and a black flocculate (3010 mg). The treated cardanols gives U tube viscosity of 65.5 cps.
Treatment of CNSL with C¾N0 2
CNSL (1 g) was also submitted to the same procedure and provided (640 mg) of a mixture of cardanols-cardols and 320 mg of a black solid. Treated CNSL gave U tube viscosity of 73.1 cps. The NMR spectrum of the resinous black flocculate was broad, and its MS-EI and IR spectra were similar to those of crude CNSL.
2-hydroxy-6-(8-hvdroxy-octyl)-benzoic acid
To a solution of anacardic acids ( 3 g, 8.6 mmol), dissolved in methanol (50 ml) - dichloromethane (50 ml), in a three-neck flask provided with a condenser and an ice-bath cooling , was bubbled ozone (43 mmol, 2 equivalents). After purging the reaction mixture with nitrogen (during 5 minutes), the mixture was cooled in an ice bath, and acetic acid ( 5.3 g , 10 equivalents) and zinc ( 5.5 , 10 equivalents) were slowly added. The resulting mixture was stirred for 4 hrs. The suspension was then filtered and the inorganic residue washed with light petroleum. The combined washing and filtrate were then concentrated under reduced pressure, to provide a brown oil, which distillate (under vacuum at 120 °C), was dissolved in ethyl acetate (10 ml) and washed with sodium bicarbonate (saturated solution) (3 x 10 ml). Aqueous layer was then acidified to pH 1 with a solution of HC1 (5 %) and re-extracted with ethyl acetate to provide the title compound (1.02 g, yield = 46 % ) identified by IR: < max (film, cm "1 ), 3300, 2980, 2719, 1724, 1650-1670, 1610, 1460, 1240, 1140, 920, 830cm 1 , 'HNMR (CD0 3 ), *H (ppm), 9.8 (s, 1H,CH0), 7.35-7-28 (t,lH,H-Ar, J= 7.625 Hz), 6.85-6.82 (d,lH,H-Ar, J= 8.225 Hz), 2.98-2.92 (pseudo-t, 2H, J; = 7.325 Hz, J2=7.625 Hz), 2.44-2.41 (dt,2H, CH2CO, J^l.525, J 2 = 7325 Hz), 1.61 (br, 2H =CCH2),1.32 (br, 7.5 H, CH 2 ), 13 C (CDCl 3 ), * H (ppm), 204.14,175.54, 163.41, 147.43,135.15, 122.68, 115.78, 110.66, 43.76, 36.35, 31.80, 29.47, 29.04, 28.99, 21.97; m/z (Iv 264, C15H20O4 requires 264).
Acetic acid 3-acetoxy-5-(8-oxo-octyl)-phenyl ester
To a solution of cardols in acetic anhydride , was added pyridine. The mixture was stirred at room temperature during 2 hrs, until the reaction was shown to be complete by thin layer chromatography (petrol-ethyl acetate, 4:1). Water was then added and the mixture was extracted with ethyl acetate. The combined extracts were washed with 5% hydrochloric acid solution, brine, dried over magnesium sulphate and evaporated. To a solution of the preceding arene (3.77 g, 9.5 mmol), dissolved in dichloromethane (100 ml) in a two-neck flask, was bubbled ozone ( 43 ml, 2 equivalents). Temperature was maintained at (- 70 °C) with a liquid nitrogen- cooling bath.After purging the reaction mixture with nitrogen (during 5 minutes), acetic acid (10 ml) and zinc ( 5 g) were added, and the mixture was stirred for 4 hrs. The suspension was then washed in sequence with sodium bicarbonate (saturated solution) until no more bubbling appeared, and distilled water (5 ml).Both layers were separated and the aqueous layer was re-extracted with dichloromethane (3 x 10 ml).The combined organic layers were allowed to dry over magnesium sulphate, filtered and concentrated under vacuum to give g of a reddish oil, which was purified by chromatography to provide (2.8 g, 92 % yield). IR (film):2719, 1724, 1604, 1587, 1498, 1261 cm "1 , 1 HNMR (CDC1 3 ) δ: 9.7 (s, 1H, HCO), 7.2-6.7 (m,3H,H-Ar), 2.62-2.56 (t, 2H, C¾-Ar), 2.44-2.41 (t, 2H, C¾-CO), 2.15 (s, CH 3 CO),1.61 (br, 2 H, =CCH 2 ,),1.32 (br, 7.5 H, CH 2 ,), 13 C (CDC1 3 ) 202.92, 169.09 (2C), 150.84 (2C), 145.18 (2C), 118.89, 112.63, 77.55, 77.04, 76.53, 43.84, 35.57, 30.70, 29.09, 21.97, 21.11.m/z =( + 320,C 18 H 24 O 5 requires 320), 278, 236.
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