The present invention relates to the technical field of methods for isolation of fractions of chemicals from plants. More specifically the invention provides a three step method for converting suberin and/or cutin containing plant parts, such as birch outer bark, into a suberin monomer containing mixture by alkali hydrolysis without use of organic solvents and isolating a fraction enriched in c/s-9,10-epoxy-18-hydroxyoctadecanoic acid together with a residual fraction containing more lipophilic hydroxyfatty acids, betulin, fupeol, and betulinic acid as major components. Also disclosed are products obtainable by said method and uses of said products and said method.

Background

The present invention relates to a method for converting plant parts into chemicals and in particular to the conversion of biopolyesters such as suberin by hydrolysis with alkali in water to give the corresponding hydroxyfatty acid monomers and isolation of a fraction enriched in c/s-9,10-epoxy-18-hydroxyoctadecanoic acid together with a residual fraction of more lipophilic hydroxyfatty acids and betulin, iupeol, and betulinic acid as major components. The suberin composition is usually complex and differs between plant species and this complexity probably explains why the use of hardwood bark as a commercial source of "green" chemicals has not been well explored. One exception to complexity is the suberin in the outer bark of birch species (deciduous trees of the genus Betula), where c/s-9,10- epoxy-18-hydroxyoctadecanoic acid is the principal monomer amounting, for example, to about 100 g/kg dry outer bark in Betula verrucosa and Betula papyrifera. Birch bark is a large volume but low value by-product in the forest industry today mainly used as fuel. c/s-9,10-Epoxy-18-hydroxyoctadecanoic acid has, for example, been used for the preparation of epoxy group containing polyesters (Olsson et al. 2007) without the use of organic solvents and converted to 9,10,18-trihydroxyoctadecanoic acid for synthesis of ambrettolide which induces musk fragrance in perfumes (E. Seone 1982). The previous described methods for hydrolysis and isolation of birch bark components all are based upon multistep procedures involving the use of organic solvents for extraction, isolation and purification in combination with evaporation (condensation) of solvents to obtain fractionated suberin monomers (Krautsky et al US 6,768,016 B2, Ekman et al. US 4,732,708). Accordingly there is a need to provide a method for isolation of c/s-9,10- epoxy-18-hydroxyoctadecanoic acid enriched fractions from suberin and/or cutin containing plant parts, such as birch outer bark, which is simpler than the previously known methods involving several steps, and eliminates the use of organic solvents. Now it has unexpectedly been found that fractions containing c/s-9,10-epoxy-18- hydroxyoctadecanoic acid as main component can be isolated from suberin and/or cutin containing plant parts, such as outer bark, from e.g. birch, by using aqueous extractions with a suitable choice of alkali charge, temperature and hydrolysis time in an uncomplicated manner. The simple three step extraction procedure combines alkaline hydrolysis of suberin, dissolution of the corresponding c/s-9,10-epoxy-18-hydroxyoctadecanoic acid sait and precipitation of the acid by acidification. This requires a careful adjustment of the hydrolysis conditions since at higher alkali charges, higher temperatures and longer hydrolysis times the sensitive epoxy group in c/s-9,10-epoxy-18-hydroxyoctadecanoic acid is converted to the corresponding dioi thus decreasing the yield of c/s-9,10-epoxy-18-hydroxyoctadecanoic acid.

Summary of the invention

The present invention solves the above problem by providing according to a first aspect a method for separating (isolating) from suberin and/or cutin containing plant parts, a solid and/or oil fraction enriched in c/s-9,10-epoxy-18-hydroxyoctadecanoic acid and at the same time leaving a residual solid fraction, comprising the following steps: a) subjecting suberin and/or cutin containing plant parts, preferably shredded, ground, chipped, muled, crushed or by any combinations thereof converted into smaller pieces, to alkaline hydrolysis, preferably by using an alkali hydroxide and/or an alkali carbonate in an aqueous solution, most preferred also involving impregnation, b) separating the aqueous solution from the residual solid phase which comprises mainly triterpenoids, such as betulin, and lipophilic suberin monomers, and c) acidifying the aqueous solution giving as a result an aqueous phase and a solid and/or oil fraction enriched in c/s-9,10-epoxy-18-hydroxyoctadecanoic acid, optionally followed by another separation step for separating said solid and/or oil fraction from the water phase, preferably by centrifugation or by filtration and finally drying.

The present invention also provides according to a second aspect a fraction enriched in c;s-9,10-epoxy-18-hydroxyoctadecanoic acid obtainable by a method according to the first aspect. The present invention also provides according to a third aspect use of the fraction enriched in c/s-9,10-epoxy-18-hydroxyoctadecanoic acid according to the second aspect in the manufacture (synthesis) of epoxy functionaNzed polyesters or co-pofyesters.

The present invention also provides according to a fourth aspect use of the fraction enriched in c/s-9, 10-epoxy-18-hydroxyoctadecanoic acid according to the second aspect in a perfume composition or manufacture thereof.

The present invention also provides according to a fifth aspect a residual solid fraction comprising lipophilic hydroxyfatty acids, betulin, lupeol, betulinic acid, or combinations thereof obtainable by a method according to the first aspect. The present invention also provides according to a sixth aspect use of a residual solid fraction comprising lipophilic hydroxyfatty acids, betulin, lupeol, betulinic acid, or combinations thereof according to the fifth aspect in a pharmaceutical or cosmetic composition or for manufacture thereof or for manufacture of a component thereof.

The present invention also provides according to a seventh aspect use of the method according to the first aspect in a process parallel to a chemical pulping process which uses birch wood as one of the raw materials.

The purpose of the present invention is, particularly, to support the refined use of byproducts from forest industries such as birch outer bark and oak cork and also potato peels {from food industries) and similar suberin and/or cutin containing plant parts to obtain renewable chemicals.

Detailed description of the invention

It is intended throughout the present description that the expression "suberin and/or cutin containing plant parts" embraces parts of any plant species containing an amount of suberin and/or cutin. Preferably this plant part is a hardwood bark which may be birch outer bark (which is suitable) or oak cork or potato peels.

It is intended throughout the present description that the expression "alkali hydroxide" embraces sodium hydroxide (NaOH), potassium hydroxide (KOH), lithium hydroxide (LiOH), rubidium hydroxide (RbOH) and cesium hydroxide (CsOH). Suitable metal hydroxides for suberin and/or cutin hydrolysis include sodium hydroxide (NaOH) ₁ potassium hydroxide (KOH) and lithium hydroxide (LiOH). It is intended throughout the present description that the expression "alkali carbonate" embraces sodium carbonate (Na ₂ CO ₃ ), potassium carbonate (K ₂ CO ₃ ), lithium carbonate (Li ₂ COa), rubidium carbonate (Rb ₂ COs) and cesium carbonate (CS ₂ CO3). The metal hydroxide used in the examples of this patent is sodium hydroxide since it is compatible with the chemical recovery systems used in most chemical pulp mills producing e.g. birch pulp.

According to a preferred embodiment of the first aspect of the present invention there is provided a method wherein the acidifying in step c) provides a pH above 3, preferably a pH above 5, most preferred a pH above 6.

According to a preferred embodiment of the first aspect of the present invention there is provided a method wherein the acidifying in step c) comprises keeping said separated aqueous solution at a temperature below 100 ⁰ C. According to a preferred embodiment of the first aspect of the present invention there is provided a method wherein the temperature in step c) is from -20 to 8O ⁰ C.

According to a preferred embodiment of the first aspect of the present invention there is provided a method wherein the separation in step b) is carried out by filtration or by centrifugation. According to a preferred embodiment of the first aspect of the present invention there is provided a method wherein the suberin and/or cutin containing plant parts are from a hardwood bark, preferably birch outer bark.

According to a preferred embodiment of the first aspect of the present invention there is provided a method wherein step a) is performed from about 10 minutes to about 3 hours, preferably from about 30 minutes to about 90 minutes.

According to a preferred embodiment of the first aspect of the present invention there is provided a method wherein the alkali hydroxide of step a) is sodium hydroxide.

According to a preferred embodiment of the first aspect of the present invention there is provided a method wherein the temperature of step a) is from about 50 to about 15O ⁰ C, preferably from about 80 to about 120 ⁰ C.

According to a preferred embodiment of the first aspect of the present invention there is provided a method according to claim 1 wherein the separation of step b) is preceded by cooling.

According to a preferred embodiment of the first aspect of the present invention there is provided a method wherein lupeol, betulinic acid and/or betulin and other lipophilic extractives are removed from the suberin and/or cutin containing plant parts prior to the hydrolysis. According to a preferred embodiment of the first aspect of the present invention there is provided a method wherein the hydrolysis in step a) is carried out using from 0.1 to 5 M NaOH (aq), preferably from 0.25 to 2.2 M NaOH <aq), most preferred from 0.5 to 1.0 M NaOH (aq) for obtaining the solid and/or oil fraction enriched in c/s-9,10-epoxy-18- hydroxyoctadecanoic acid.

According to a preferred embodiment of the first aspect of the present invention there is provided a method wherein the hydrolysis in step a) is carried out using a sodium hydroxide charge from 0.4 to 20 g per 10 g birch outer bark, preferably from 1 to 8.8 g per 10 g birch outer bark, most preferred from 2 to 4 g per 10 g birch outer bark for obtaining the solid and/or oil fraction enriched in c/s-9,10-epoxy-18-hydroxyoctadecanoic acid.

According to a preferred embodiment of the first aspect of the present invention there is provided a method wherein the alkali carbonate of step a) is sodium carbonate.

According to a preferred embodiment of the first aspect of the present invention there is provided a method wherein said treatment with sodium carbonate is performed at a temperature from about 60 to 18O ⁰ C, preferably from about 90 to 160°C.

According to a preferred embodiment of the first aspect of the present invention there is provided a method wherein the hydrolysis in step a) is carried out using from 0.1 to 5 M Na ₂ CO ₃ (aq), preferably from 0.25 to 2.2 M Na ₂ CO ₃ (aq), most preferred from 0.5 to 1.0 M Na ₂ CO ₃ (aq) for obtaining the solid and/or oil fraction enriched in c/s-9,10-epoxy-18- hydroxyoctadecanoic acid.

According to a preferred embodiment of the first aspect of the present invention there is provided a method wherein the obtained c/s-9,10-epoxy-18-hydroxyoctadecanoic acid has a purity above 30% in the solid and/or oil fraction, preferably a purity above 50%, most preferred above 70%. The examples in the present application are based on the use of birch outer bark but other suberin and/or cutin containing barks and plant parts can be used in an analogous approach.

Preferred features of each aspect of the invention are as for each of the other aspects mutatis mutandis. The prior art documents mentioned herein are incorporated to the fullest extent permitted by law. The invention is further described in the following examples which do not limit the scope of the invention in any way. Embodiments of the present invention are described in more detail with the aid of examples of embodiments, the only purpose of which is to illustrate the invention and are in no way intended to limit its extent. The yields below are estimated by ¹ H NMR. Examples

Example 1 (0.8 M NaOH 100 ml, 100 ⁰ C, 1h) 10 g of dry milled (60 mesh) birch outer bark was charged to a glass flask containing a solution of 3.3 g sodium hydroxide in 100 ml water. To impregnate the bark powder with the alkaline solution the flask was evacuated under stirring for 10 minutes (water pump). The reaction mixture was refluxed for 1 hour, allowed to cool to room temperature and the residual solid removed by centrifugation. The resulting aqueous solution was acidified to a pH above 6 and kept in a refrigerator overnight, the solids were isolated by centrifugation and freeze dried to give c/s-9,10-epoxy-18-hydroxyoctadecanoic acid of 72% purity.

Example 2 (0.8 M NaOH 100 ml, 100 ⁰ C, 3h) 10 g of dry milled (60 mesh) birch outer bark was charged to a glass flask containing a solution of 3.3 g sodium hydroxide in 100 ml water. To impregnate the bark powder with the alkaline solution the flask was evacuated under stirring for 10 minutes (water pump). The reaction mixture was refluxed for 3 hours, allowed to cool to room temperature and the residual solid removed by centrifugation. The resulting aqueous solution was acidified to a pH above 6 and kept in a refrigerator overnight, the solids were isolated by centrifugation and freeze dried to give c/s-9,10-epoxy-18-hydroxyoctadecanoic acid of 51% purity.

Example 3 (0.8 M NaOH 100 ml, 130 ⁰ C, 1 h) 10 g of dry milled (60 mesh) birch outer bark was charged to a reactor containing a solution of 3.3 g sodium hydroxide in 100 ml water. To impregnate the bark powder with the alkaline solution the reactor was evacuated under stirring for 10 minutes (water pump). The reaction mixture was kept at 130 ⁰ C for 1 hour, ailowed to cool to room temperature and the residual solid removed by centrifugation. The resulting aqueous solution was acidified to a pH above 6 and kept in a refrigerator overnight, the solids were isolated by centrifugation and freeze dried to give c/s-9,10-epoxy-18-hydroxyoctadecanoic acid of 39% purity.

Example 4 (1.0 M NaOH 100 ml, 100 ⁰ C, 1h) 10 g of dry milled (60 mesh) birch outer bark was charged to a glass flask containing a solution of 4 g sodium hydroxide in 100 ml water. To impregnate the bark powder with the alkaline solution the flask was evacuated under stirring for 10 minutes (water pump). The reaction mixture was refiuxed for 1 hour, allowed to cool to room temperature and the residual solid removed by centrifugation. The resulting aqueous solution was acidified to a pH above 6 and kept in a refrigerator overnight, the solids were isolated by centrifugation and freeze dried to give c/s-9, 10-epoxy-18-hydroxyoctadecanoic acid of 53% purity.

Example 5 (1.O M NaOH 50 ml, 100 ⁰ C, 1h)

10 g of dry milled (60 mesh) birch outer bark was charged to a glass flask containing a solution of 2 g sodium hydroxide in 50 ml water. To impregnate the bark powder with the alkaline solution the flask was evacuated under stirring for 10 minutes (water pump). The reaction mixture was refiuxed for 1 hour, allowed to coo! to room temperature and the residual solid removed by centrifugation. The resulting aqueous solution was acidified to a pH above 6 and kept in a refrigerator overnight, the solids were isolated by centrifugation and freeze dried to give c/s-9, 10-epoxy-18-hydroxyoctadecanoic acid of 71 % purity.

Example 6 (0.4 M NaOH 100 ml, 100 ⁰ C, 1 h)

10 g of dry milled (60 mesh) birch outer bark was charged to a glass flask containing a solution of 1.63 g sodium hydroxide in 100 ml water. To impregnate the bark powder with the alkaline solution the flask was evacuated under stirring for 10 minutes (water pump). The reaction mixture was refiuxed for 1 hour, allowed to cool to room temperature and the residual solid removed by centrifugation. The resulting aqueous solution was acidified to a pH above 6 and kept in a refrigerator overnight, the solids were isolated by centrifugation and freeze dried to give c/s-9, 10-epoxy-18-hydroxyoctadecanoic acid of 21% purity.

Example 7 (1.5 M NaOH 100 ml, 100 ⁰ C, 1 h)

10 g of dry milled (60 mesh) birch outer bark was charged to a giass flask containing a solution of 6 g sodium hydroxide in 100 ml water. To impregnate the bark powder with the alkaline solution the flask was evacuated under stirring for 10 minutes (water pump). The reaction mixture was refiuxed for 1 hour, allowed to cool to room temperature and the residual solid removed by centrifugation. The resulting aqueous solution was acidified to a pH above 6 and kept in a refrigerator overnight, the solids were isolated by centrifugation and freeze dried to give c/s-9, 10-epoxy-18-hydroxyoctadecanoic acid of 47% purity. Example 7 {2.0 M NaOH 100 ml, 100 ⁰ C, 1h)

10 g of dry milled (60 mesh) birch outer bark was charged to a glass flask containing a solution of 8 g sodium hydroxide in 100 ml water. To impregnate the bark powder with the alkaline solution the flask was evacuated under stirring for 10 minutes (water pump). The reaction mixture was refluxed for 1 hour, allowed to cool to room temperature and the residual solid removed by centrifugation. The resulting aqueous solution was acidified to a pH above 6 and kept in a refrigerator overnight, the solids were isolated by centrifugation and freeze dried to give c/s-9, 10-epoxy-18-hydroxyoctadecanoic acid of 31% purity.

Example 8 (2.5 M NaOH 100 ml, 100 ⁰ C, 1 h)

10 g of dry milled (60 mesh) birch outer bark was charged to a glass flask containing a solution of 10 g sodium hydroxide in 100 ml water. To impregnate the bark powder with the alkaline solution the flask was evacuated under stirring for 10 minutes (water pump). The reaction mixture was refluxed for 1 hour, allowed to cool to room temperature and the residual solid removed by centrifugation. The resulting aqueous solution was acidified to a pH above 6 and kept in a refrigerator overnight, the solids were isolated by centrifugation and freeze dried to give c/s-9,10-epoxy-18-hydroxyoctadecanoic acid of 10% purity.

The above examples demonstrate that by carefully adjusting temperature, alkali charge and hydrolysis time it is possible to obtain fractions with the sodium salt of c/s-9,10- epoxy-18-hydroxyoctadecanoic acid as the main component.

Various embodiments of the present invention have been described above but a person skilled in the art realizes further minor alterations, which would fall into the scope of the present invention. The breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents. For example, any of the above- noted methods can be combined with other known methods. Other aspects, advantages and modifications within the scope of the invention will be apparent to those skilled in the art to which the invention pertains.

List of documents appearing in the description "Lipase-Catalyzed Synthesis of an Epoxy-Functionalized Polyester from the Suberin Monomer 9, IO-epoxy-18-hydroxyoctadecanoic acid", A. Oisson, M. ϋndstrόm, T. Iversen, Biomacromolecules 2007, 8, 757-760

"Synthesis of Ambrettolide from Phloionoic Acid", E. Seone, Journal of Chem. Soc. Perkin. Trans., 1982, 1837-1839

US 6,768,016 and

US 4,732,708