The first object of the invention is xanthone derivatives containing cinnamoyl, 2-ethylhexylidene or the corresponding benzylidene or cinnamylidene residues. The second object of the invention is a UV protective composition concentrate. The third object of the invention is a method for preparing a UV protective composition concentrate. The next object of the invention is the use of a UV protective composition concentrate for the production of cosmetic UV protective products. Yet another object of the invention is a cosmetic UV protective product.

The international PCT patent application W02009024087A1 discloses a method of surface modification by obtaining polymers directly on a substrate. The modification is carried out by radical polymerization of compounds (units) containing a xanthone derivative. "UV filters" are substances that are designed solely or primarily to protect the skin against certain types of ultraviolet radiation which may be absorbed, reflected or diffused by them. Currently, 26 organic filters are approved for use in the European Union. Despite high safety requirements, it has been shown that some of them, such as oxybenzone, octinoxate, 3-(4- methylbenzylidene)camphor penetrate into the deeper layers of the skin, from where they enter the bloodstream [1-4]. Additionally, the literature describes that they may contribute to endocrine disorders, adversely affect the viability of nerve cells, and induce some allergic reactions [5-8] A significant problem is also the low photostability of some of them [9,10] In recent years, due to the unsatisfactory safety profile, two UV filters were withdrawn from use, i.e. p-aminobenzoic acid and 3-benzylidene camphor [11,12] Taking into account the fact that the use of photoprotective preparations is of great preventive importance when it comes to the development of skin cancers, it seems necessary to develop new effective and safe UV filters. An interesting group of compounds that can find such application and meet the desired safety profile are, among others, xanthone derivatives. Some of them are already used in cosmetics as skin conditioning substances, e.g. mangiferin, 2-(l-methylethyl)thioxanthone. It would be a technical problem to provide compounds that could be used as UV filters in cosmetic products, characterized by high photostability, permanent sun protection in the UVB and/or UVA range, and should be safe to use, without causing both local and systemic undesirable reactions. The first object of the invention is a xanthone derivative described by the formula (I) where:

- Ri is a substituent selected from the group comprising: a hydrogen atom or an alkoxy group,

- R ₂ is a substituent selected from the group comprising: methylcinnamoyl, cyano-2,4- dienopentaphenyl, cyanoethenylphenyl or cyanoethenylalkyl substituent, wherein the phenyl ring is substituted with R ₃ substituent selected from the group comprising: hydrogen atom, alkoxy substituent or halide atom.

In a preferred embodiment of the invention, the phenyl substituent on methylcinnamoyl, cyano- 2,4-dienopentaphenyl or cyanoethenylphenyl substituent is substituted with R ₃ substituent selected from the group comprising: hydrogen atom, methoxy group or halide atom selected from the group comprising: fluorine, chlorine, bromine or iodine, wherein the methoxy substituent or the halide atom is substituted at the 2, 3 or 4 position.

In a further preferred embodiment of the invention, the xanthone derivative is substituted with R ₂ substituent selected from the group comprising: methylcinnamoyl, cyano-2,4- dienepentaphenyl, cyanoethenylphenyl or cyanoethenylalkyl substituent at the 2- or 4-position.

In yet another preferred embodiment of the invention, the xanthone derivative is substituted with Ri substituent selected from the group comprising: hydrogen atom or methoxy substituent, wherein the methoxy substituent is substituted at the 6-position.

In another embodiment of the invention, the cyanoethenylalkyl substituent comprises a branched chain alkyl. The second object of the invention is a UV protective composition concentrate containing a xanthone derivative described by the formula (I) where: - Ri is a substituent selected from the group comprising: a hydrogen atom or an alkoxy group,

- R ₂ is a substituent selected from the group comprising: methylcinnamoyl, cyano-2,4- dienopentaphenyl, cyanoethenylphenyl or cyanoethenylalkyl substituent, wherein the phenyl ring is substituted with R ₃ substituent selected from the group comprising: hydrogen atom, alkoxy substituent or halide atom, wherein the xanthone derivative content to triacetin content ratio in the concentrate is from 3:1 to 1:3 parts by weight.

In a further preferred embodiment of the invention, the concentrate contains triacetin in a weight ratio of 1:1 relative to the xanthone derivative according to formula (I).

The third object of the invention is a method for the preparation of a UV protective composition concentrate containing a xanthone derivative described by the formula (I) characterized in that 1 to 3 parts of the derivative of the compound described by the formula (I) are added to 1 to 3 parts by weight of triacetin, mixed and then milled for 12 hours.

In another preferred embodiment of the invention, the milling is carried out in cycles of 20 minutes of milling and 10 minutes of pause period. In another preferred embodiment of the invention, the milling is carried out in a planetary ball mill, wherein the rotation speed of the disc is 400 rpm. Another object of the invention is the use of a UV protective composition concentrate containing a xanthone derivative described by the formula (I) for the production of cosmetic UV protective products. Another object of the invention is a cosmetic UV protective product, characterized in that it contains a macrogol cream base and a UV protective composition concentrate containing the xanthone derivative represented by formula (I).

In yet another preferred embodiment of the invention, the cosmetic UV protective product contains the xanthone derivative (I) in an amount of 5% to 12.5% by weight. In a further preferred embodiment of the invention, the macrogol base contains an oxyethylene glycol of molecular weight of 400 (PEG 400) and an oxyethylene glycol of molecular weight of 1500 (PEG 1500).

In yet another preferred embodiment of the invention, the weight ratio of oxyethylene glycol of molecular weight of 400 (PEG 400) and an oxyethylene glycol of molecular weight of 1500 (PEG 1500) is 1:1.

Embodiments of the invention are shown in Figures, where: Fig. 1 shows the synthesis of xanthone derivatives with a methylcinnamolyl substituent; Fig. 2 shows the synthesis of derivatives with cyano-2,4-dienopentaphenyl, cyanoethenylphenyl or cyanoethenylalkyl substituents; Fig. 3a and 3b show UV absorption curves of chloroform solutions of compounds 1- 5 and octocrylene and octinoxate (EHMC); Fig. 4 shows UV absorption curves of chloroform solutions of compounds 6-9 and avobenzone; Fig. 5 shows UV absorption curves of chloroform solutions of compound 10 and octocrylene.

The invention has a number of advantages. A number of compounds from the group of xanthone derivatives with a different biological activity profile have been obtained, including potential UV radiation absorbers. The described xanthone derivatives are UV radiation filters with a wide absorption range (maximum absorption and high absorption intensity). They are characterized by high and durable sun protection in the range of UVB and/or UVA, and are also safe to use, without causing both local and systemic adverse reactions.

The manufactured cosmetic products, in addition to the compounds according to the invention, may also contain other cosmetically acceptable substances used to prepare appropriate forms of formulations applied to the skin (e.g. creams, gels, lotions, aerosols, etc.)

I. Description of the synthesis of intermediates

1. 2- or 4-methylxanthone, 6-chloro-2- or 4-methylxanthone

200 mL of solution of sodium ethoxide (0.4 mol of sodium) was prepared in a 500 mL round bottom flask to which was added 0.2 mol of 2-chlorobenzoic or 2,4-dichlorobenzoic acid and 0.2 mol of 2- or 4-methylphenol, respectively. After the ethanol had been distilled off, the mixture was heated in a mixture of paraffin oil in the presence of metallic copper (0.02 g) and copper (I) oxide (0.05 g) for 1.5 hours at a temperature of 200-210 °C. After completion of the reaction, the precipitate was filtered out from the oil and then washed with toluene. After drying the precipitate, it was dissolved in hot water and, after heating it with activated carbon, it was filtered out from the suspension. Upon acidification, a crude condensation product precipitated and, after drying, was cyclized with concentrated sulfuric acid. The reaction was carried out for 2 hours in a boiling water bath. After completion of the reaction, the cyclization product was isolated by pouring the reaction mixture into a beaker containing ice, which, after filtration, was treated with 10% NaOH to remove any unreacted starting material. After drying, the crude product was crystallized from ethanol to obtain the corresponding xanthone derivatives with a yield of 55- 67%. The physicochemical properties of the obtained derivatives are consistent with the literature data [13-15], including the data for compounds previously obtained at the Department of Bioorganic Chemistry of the Jagiellonian University Medical College.

2. 6-methoxy-2- or 4-methylxanthone Sodium methoxide solution (S00 mL of methanol, 20 g of sodium) was prepared in a 500 mL round bottom flask to which was added 20 g of 6-chloro-2- or 4-methylxanthone. The reaction mixture was heated in a water bath under reflux for about 25 hours. It was then concentrated to dryness and, after dilution with water, acidified with 20% H2SO4. After filtration and washing with water, the reaction product was dried and recrystallized from toluene. The physicochemical properties of the respective xanthone derivatives are consistent with the literature data [13,16,17], the yield remained about 70%.

3. 2 or 4-bromomethylxanthone, 6-methoxy-2- or 4-bromomethylxanthone

0.08 mol of the appropriate methyl derivative of xanthone, 0.082 mol of /V-bromosuccinimide, 0.15 g of benzoyl peroxide and 200 mL of carbon tetrachloride were placed in a 500 mL round bottom flask. The reagent mixture was heated in a water bath under reflux for about 10 hours under irradiation. After completion of the reaction, the CCU-soluble reaction product was filtered out from the sparingly soluble succinimide, and after cooling the filtrate, a crystalline, light cream precipitate of appropriate 2- or 4-bromo derivatives of xanthone was separated and crystallized twice from a 4:1 toluene/heptane mixture, with a yield of 56-64%. The physicochemical properties for both 2- and 4-bromomethylxanthone as well as 6-methoxy-2- and 4- bromomethylxanthone were consistent with the literature data [13,18,19] 4. 2- or 4-cyanomethylxanthone and 6-methoxy-2-cyanomethylxanthone 0.02 mol of the appropriate bromo derivative of xanthone was placed in a 250 mL round-bottom flask and 150 mL of ethanol and 25 mL of a hot KCN solution in water (0.04 mol) were added. The mixture was heated to reflux for 6 hours. After completion of the reaction, the solvent was distilled off to obtain a dry residue, and then about 100 mL of water was added, and after heating the desired compound was filtered off, which after drying was crystallized from toluene/petroleum ether 5:1. The obtained acetonitriles were recrystallized from ethanol to obtain compounds with physicochemical parameters corresponding to the literature data [13,15] The reaction yield ranged from 50-56%. III. Synthesis of xanthone derivatives and physicochemical characterization of compounds according to the invention

The obtained derivatives are summarized in Table 1.

Table 1. Structures of compounds according to the invention.

1. Synthesis of ester derivatives of xanthone containing cinnamoyl residues (1 - 5), Fig. 1.

0.01 mol of the appropriate bromo derivative of xanthone was placed in a 50 mL conical flask, then 0.011 mol of the appropriate cinnamic acid derivative, 1 g of potassium carbonate and 20 mL of DMF were added. The reaction was carried out for 8 hours at room temperature while stirring continuously using a magnetic stirrer. After completion of the reaction, the mixture was poured into ice, and the resulting precipitate was filtered and washed with 5% sodium bicarbonate solution and distilled water. After drying, the precipitate was crystallized from toluene:heptane 2:1 with the addition of silica gel. The reaction yield ranged from 64-76%. (6-Methoxy-9-oxo-9H-xanthen-2-yl)methyl (E)-3-(4-methoxyphenyl)acrylate (1) was obtained as a white solid, MW = 416.43, mp 169-171 °C, ^X H NMR (300 MHz, Chloroform-d) d 8.38 - 8.33 (m, 1H, X-Hl), 8.24 (d, J = 8.9 Hz, 1H, X-H8), 111 - 7.72 (m, 1H, X-H3), 7.69 (d, J = 15.9 Hz, 1H, =CH-), 7.51 - 7.43 (m, 3H, X-H4, X-H6, Ph-H2), 6.96 (d, J = 2.4 Hz, 1H, X-H5), 6.93 (d, J = 2.4 Hz, 1H, X-H7), 6.91 - 6.83 (m, 2H, Ph-H3, Ph-H5), 6.40 - 6.32 (m, 1H, -CH=), 5.33 (s, 2H, -CH ), 3.93 (s, 3H, -OCH ₃ ), 3.82 (s, 3H, -OCH ₃ ), ESI-MS [M+H] ⁺ m/z calculated/determined 417.43/417.23, 99.14%.

(6-Methoxy-9-oxo-9H-xanthen-4-yl)methyl (E)-3-(4-chlorophenyl)acrylate (2) was obtained as a white solid, MW = 420.85, mp 202-203 °C, ^X H NMR (300 MHz, Chloroform-d) d 8.33 (dd, J = 8.0, 1.8 Hz, 1H, X-Hl), 8.25 (d, J = 8.8 Hz, 1H, Ph-H5), 7.81 (dd, J = 7.4, 1.8 Hz, 1H, X-H2), 7.72 (d, J = 16.0 Hz, 1H, =CH-), 7.46 (d, J = 8.5 Hz, 2H, Ph-H2, Ph-H6), 7.40 (d, J = 7.6 Hz, 1H, X-H8), 7.36 (d, J = 3.1 Hz, 1H, Ph-H3), 7.34 (s, 1H, X-H5), 6.98 (d, J = 2.4 Hz, 1H, X-H7), 6.96 - 6.91 (m, 1H, X-H3), 6.50 (d, J = 16.0 Hz, 1H, -CH=), 5.63 (s, 2H, -CH ), 3.94 (s, 3H, -OCH ₃ ), ESI-MS [M + H] ⁺ m/z calculated/determined 421.85/421.15, 100%.

(6-Methoxy-9-oxo-9H-xanthen-2-yl)methyl (E)-3-(2,4-dimethoxyphenyl)acrylate (3) was obtained as a white solid, MW = 446.46, mp 194-195, ^X H NMR (300 MHz, Chloroform-d) d 8.40 - 8.34 (m, 1H, X-Hl), 8.25 (d, J = 8.9 Hz, 1H, Ph-H5), 7,95 (d, J = 16.1 Hz, 1H, =CH-), 7.75 (dd, J = 8.6,

2.3 Hz, 1H, X-H3), 7.45 (t, J = 8.4 Hz, 2H, X-H4, X-H8), 6.95 (dd, J = 8.9, 2.4 Hz, 1H, X-H7), 6.89 (d, J = 2.4 Hz, 1H, X-H5), 6.56 - 6.45 (m, 2H, Ph-H3, -CH=), 6.44 (d, J = 2.4 Hz, 1H, Ph-H5), 5.33 (s, 2H, -CH ₂ ), 3,94 (s, 3H, -OCHs), 3.86 (s, 3H, -OCH ₃ ), 3.83 (s, 3H, -OCH ₃ ), ESI-MS [M+H] ⁺ m/z calculated/determined 447.46/447.20, 98.69%. (6-Methoxy-9-oxo-9H-xanthen-2-yl)methyl (E)-3-(3,4-dimethoxyphenyl)acrylate (4) was obtained as a white solid, MW = 446.46, mp 189-190 °C, ^X H NMR (300 MHz, Chloroform-d) d 8.41 - 8.34 (m, 1H, X-Hl), 8.25 (d, J = 8.9 Hz, 1H, X-H8), 7.74 (dd, J = 8.6, 2.3 Hz, 1H, X-H3), 7.68 (d, J = 15.9 Hz, 1H, =CH-), 7.51 - 7.42 (m, 1H, X-H7), 7.15 - 7.02 (m, 2H, X-H4, X-H5), 7.00 - 6.92 (m, 1H, Ph-H5), 6.92 - 6.81 (m, 2H, Ph-H2, Ph-H6), 6.37 (d, J = 15.9 Hz, 1H, -CH=), 5.34 (s, 2H, -CH ₂ ), 3.96 - 3.85 (m, 9H, 0-CH ₃ , 0-CH ₃ , 0-CH ₃ ), ESI-MS [M+H] ⁺ m/z calculated/determined 447.46/447.14,

96.99%.

(6-Methoxy-9-oxo-9H-xanthen-2-yl)methyl (E)-3-(2,3,4-trimethoxyphenyl)acrylate (5) was obtained as a white solid, MW = 476.48, mp 188-190 °C, ^X H NMR (300 MHz, Chloroform-d) d 8.39 (dd, J = 2.3, 0.6 Hz, 1H, X-Hl), 8.26 (d, J = 8.9 Hz, 1H, X-H8), 7.74 (dd, J = 8.6, 2.3 Hz, 1H, X-H3), 7.65 (d, J = 15.9 Hz, 1H, =CH-), 7.48 (d, J = 8.6 Hz, 1H, X-H7), 7.29 - 7.23 (m, 1H, X-H4), 7.01 - 6.93

(m, 1H, Ph-H2), 6.90 (d, J = 2.4 Hz, 1H, X-H5), 6.76 (s, 1H, Ph-H6), 6.42 (d, J = 15.9 Hz, 1H, -CH=),

5.35 (s, 2H, -CH ₂ ), 3.94 (s, 3H, -OCH ₃ ), 3.88 (d, J = 2.0Hz, 9H, -OCH ₃ , -OCH ₃ , -OCH ₃ ), ESI-MS [M+H] ⁺ m/z calculated/determined 477.48/477.18, 100%.

2. Synthesis of arylidene derivatives of xanthone containing cinnamylidene (6-7) or benzylidene (8-9) residues, Fig. 2.

0.005 mol of the appropriate 2- or4-cyanomethylxanthone was placed in a 250 mL round bottom flask and then dissolved in anhydrous ethanol at reflux. Then, 10 drops of a 5% solution of sodium hydroxide in methanol and 0.005 mol of the appropriate aldehyde were added. The mixture was heated for 1 hour under reflux until a precipitate formed, which was filtered while hot. After drying, the crude solid was crystallized from ethanol or acetic acid (7). The yield ranged from 76 to 80%.

5-(2-Methoxyphenyl)-2-(9-oxo-9H-xanthen-2-yl)penta-2,4-di enenitrile (6) was obtained as yellow solid, MW = 379.42, mp 227-228 °C, ^X H NMR (300 MHz, Chloroform-d) d 8.59 - 8.43 (m, 1H, X-H8), 8.41 - 8.28 (m, 1H, =CH-), 7.98 (dd, J = 8.8, 2.5 Hz, 1H, X-H3), 7.91 - 7.70 (m, 1H, Ph-

H6), 7.69 - 7.50 (m, 4H, X-H7, X-Hl, =CH-, -CH=), 7.50 - 7.45 (m, 2H, X-H5, X-H4), 7.45 - 7.35 (m, 1H, X-H6), 7.35 - 7.21 (m, 1H, Ph-H4), 7.06 - 6.84 (m, 2H, Ph-H3, Ph-H5), 3.93 (s, 3H, -OCH ₃ ), ESI- MS [M+H] ⁺ m/z calculated/determined 380.42/380.21, 100%.

5-(4-Methoxyphenyl)-2-(9-oxo-9H-xanthen-2-yl)penta-2,4-di enenitrile (7) was obtained as yellow solid, MW = 379.42, mp 217-219 °C, ^X H NMR (300 MHz, Chloroform-d) d 8.54 (d, J = 2.4 Hz, 1H, X-H8), 8.41 - 8.31 (m, 1H, =CH-), 7.97 (dd, J = 8.8, 2.5 Hz, 1H, X-H3), 7.76 (ddd, J = 8.7, 7.1, 1.7 Hz, 1H, X-H6), 7.61 - 7.47 (m, 5H, X-H5, X-H4, X-Hl, Ph-H2, Ph-H6), 7.41 (ddd, J = 8.1, 7.1, 1.1 Hz, 1H, X-H7), 7.35 - 7.20 (m, 1H, -CH=), 7.04 (d, J = 15.3 Hz, 1H, =CH-), 6.98 - 6.87 (m, 2H, Ph-H3, Ph-H5), 3.86 (s, 3H, -OCH ₃ ), ESI-MS [M+H] ⁺ m/z calculated/determined 380.42/380.14, 98.20%. 3-(2,4-Dimethoxyphenyl)-2-(9-oxo-9H-xanthen-4-yl)acrylonitri le (8) was obtained as a pale yellow solid, MW = 383.40, mp 250-251, ^X H NMR (300 MHz, Chloroform-d) d 8.37 (ddd, J = 9.3, 8.1, 1.8 Hz, 3H, X-Hl, X-H8, X-H3), 7.99 (s, 1H, =CH-), 7.86 (dd, J = 7.5, 1.7 Hz, 1H, X-H2), 7.76 (ddd, J = 8.7, 7.1, 1.7 Hz, 1H, X-H6), 7.61 (dd, J = 8.5, 1.1 Hz, 1H, X-H5), 7.49 - 7.33 (m, 2H, X-H7, Ph-H6), 6.66 (dd, J = 8.7, 2.4 Hz, 1H, Ph-H5), 6.51 (d, J = 2.4 Hz, 1H, Ph-H3), 3.89 (d, J = 7.7 Hz, 6H, -O-CH3, O-CH3), ESI-MS [M+H] ⁺ m/z calculated/determined 384.40/384.13, 100%.

3-(3,4-Dimethoxyphenyl)-2-(9-oxo-9H-xanthen-4-yl)acryloni trile (9) was obtained as a pale yellow solid, MW = 383.40, mp 230-231 °C, ^X H NMR (300 MHz, Chloroform-d) d 8.37 (ddd, J = 14.3, 8.0, 1.7 Hz, 2H, X-Hl, X-H8), 7.85 (dd, J = 5.8, 2.0 Hz, 1H, Ph-H6), 7.82 (d, J = 1.7 Hz, 1H, X- H3), 7.76 (ddd, J = 8.6, 7.1, 1.7 Hz, 1H, X-H6), 7.61 (dd, J = 8.5, 1.1 Hz, 1H, X-H7), 7.50 - 7.33 (m, 4H, X-H5, X-H2, =CH-, Ph-H5), 6.97 (d, J = 8.4 Hz, 1H, Ph-H2), 4.01 (s, 3H, -OCH3), 3.98 (s, 3H, -

OCH3), ESI-MS [M+H] ⁺ m/z calculated/determined 384.40/384.13, 100%.

3. Synthesis of an alkylidene derivative of xanthone containing a 2-ethylhexylidene residue (10) 0.005 mol of 6-methoxy-2-cyanomethylxanthone was placed in a 250 mL round bottom flask and then dissolved in anhydrous ethanol at reflux temperature. Then, 10 drops of a 5% solution of sodium hydroxide in methanol and 0.005 mol of 2-ethylhexanal were added. The whole mixture was heated to reflux for approximately 1 hour. After the reaction was completed, the mixture was heated with activated carbon. After filtering from the suspension and concentrating the filtrate, 10 was isolated and recrystallized from ethanol. The reaction yield was 64%.

(Z)-4-Ethyl-2-(6-methoxy-9-oxo-9H-xanthen-2-yl)oct-2-enen itrile (10) was obtained as a white solid, MW = 375,47, mp 145-147°C, ^X H NMR (500 MHz, Chloroform-d) d ppm 8.44 (d, J= 2.58 Hz, 1 H, X-Hl), 8.24 (d, .7=9.16 Hz, 1 H, X-H8), 7.87 (dd, 7=8.88, 2.58 Hz, 1 H, X-H3), 7.49 (d, 7=8.59 Hz, 1 H, X-H4), 6.95 (dd, 7=8.88, 2.58 Hz, 1 H, X-H5), 6.88 (d, J= 2.29 Hz, 1 H, X-H7), 6.71 (d, 7=10.60

Hz, 1 H, =CH-), 3.93 (s, 3 H, -OCH ₃ ), 2.68 - 2.78 (m, 1 H, CH), 1.54 - 1.71 (m, 2 H, -CH ), 1.36 - 1.49 (m, 2 H, -CH ₂ ), 1.21 - 1.38 (m, 4 H, -CH ₂ -CH ₂ -), 0.95 (t, 7=7.45 Hz, 3 H, -CH ₃ ), 0,85 - 0,91 (m, 3 H, - CH ₃ ), ESI-MS [M+H] ⁺ m/z calculated/determined 376.47/376.29, 100%.

IV. Characterization of the photoprotective properties of compounds 1-10 according to the invention.

The main parameters of the UV absorption curves (Table 2) in the range of 290 - 400 nm were determined in chloroform solutions of the tested compounds at concentrations from 2.5 to 30 mM using quartz cuvettes with an optical path length of 10 mm and the Hitachi U-2800 double beam spectrophotometer (Japan) with UV Solution version 2.2 software. The absorption ability is expressed as the Ei _, i extinction coefficient which relates to the theoretical absorbance value of a 1% solution of the test substance at a given wavelength measured with an optical path length of 1 cm. The Ei _, i coefficient was calculated according to the expression (I): The molar absorption coefficient (E) used to calculate the extinction coefficient E i.i was determined from the linear regression equation A = f(Cw).

Additionally, the parameter <£i,i>mean was determined. It refers to the area under the UV absorption intensity curve expressed by the extinction coefficient Ei _, i depending on the wavelength. It is calculated as the average value of the £ coefficient at a given wavelength over the entire radiation range from 290 to 400 nm. The higher the value of the index, the wider the range of the radiation protection substance, despite similar values of the extinction coefficient

3t max· Table 2. Main parameters of UV absorption curves (in CHCb) of compounds 1 - 10 and reference UV filters

The analysis of the most important parameters of the UV absorption curve of compounds 1 and 2 (Fig. 3a) containing acyl residues of 4-methoxy and 4-chlorocinnamic acids shows that they can be classified as UVB filters. Like octocrylene and octinoxate, they show an absorption maximum ( _max ) at a wavelength around 300 nm (303 and 296 nm, respectively), which corresponds to the most erythematogenic wavelength. The value of the £ extinction coefficient for compounds 1 (916) and 2 (948) is more than twice as high as that of octocrylene (396) and slightly higher than octinoxate (858), which is considered to be one of the stronger UVB filters. Compared to octinoxate, compounds 1 and 2 show a wider range of UV absorption in the 290-400 nm region (Fig. 1), which is reflected in the higher values of the <£i,i> _mean factor. Compounds 3-5 (Fig. 3b) contain cinnamoyl residues with two or three auxochromic substituents in their molecule, which are methoxy groups in the 2,4-, 3,4- and 2,3,4- position, respectively. The Ei _,i factor of compounds 3 and 4 is much higher than octocrylene and is slightly lower compared to octinoxate. In addition, compounds 3 and 4 show two absorption maxima - the first in the UVB region (299 and 301 nm), the second in the UVA II radiation range (329 and 326 nm) and are characterized by a much wider absorption range compared to the reference UV filters (Fig. 1). Compound 3 shows the highest <£i,i>mean index (360), which makes it the most broad- range filter from the group of cinnamoyl derivatives of xanthone presented. The parameters of the absorption curve for compound 5 are comparable to compounds 1 and 2 (£i _,i (304) = 898, <£i,i>mean = 326), hence it can be considered a strong absorber of UVB radiation.

Compounds 6-7 (Fig. 2), which are cinnamylidene derivatives of xanthone, can be characterized as strong UVA absorbers ( _max = 372 and 371 nm). Compared to avobenzone, which is the most commonly used UVA filter, they absorb UV radiation more widely, which is reflected in the value of the <£i,i>mean index of 677 and 690 for compounds 6 and 7 respectively, and 520 for avobenzone. The extinction coefficient 6i _,i for compounds 6 and 7 reaches high values (1197 and

1352). It exceeds not only the values obtained for octocrylene and octinoxate, but also for avobenzone. Compounds 8-9, which are benzylidene derivatives of xanthone, differ from one another in the position of the methoxy groups on the phenyl ring of the benzylidene moiety. They are characterized by a wide range of UV radiation with an absorption maximum coinciding with that of avobenzone (358 and 357 nm). The value of the Ei _, i extinction coefficient (764 and 912) is lowerthan that of avobenzone (1158), but still comparable to octinoxate (858) and significantly higher than the value measured for octocrylene (396).

Compound 10, which is 2-ethylhexylidene derivative of 6-methoxy-2-cyanomethylxanthone, can be characterized as a poor UVB filter. It has an absorption maximum at 290 nm with the extinction coefficient reaching 668, which decreases with increasing wavelength, reaching 406 at 309 nm (Fig. 3). The main parameters of the absorption curve ( _max , £i,i, <£i,i>mean) listed in Table 2 are similar to octocrylene.

V. Examples of semi-solid UVB protective compositions containing compound 1 in the form of nanostructures The preparation of the UV protective composition consisted of three steps. The first step was to develop a concentrate containing nanoparticles of compound 1 (point 1). In the second step, a macrogol cream base was prepared (point 2). In the third step, the above-mentioned concentrate was added to the cream base (point 3).

1. The method of preparing a concentrate containing nanoparticles of compound 1 a. with a concentration of 25% (w/w)

25 parts by weight of compound 1 (white powder) was mixed with 75 parts by weight of triacetin. The system was milled in a planetary ball mill (Pulverisette 7, Fritsch) for 12h. Milling was performed in cycles of 20 minutes, followed by stopping the mill for 10 minutes. The rotation speed of the milling disc was 400 rpm. The milling resulted in a white suspension. b. with a concentration of 50% (w/w)

50 parts by weight of compound 1 (white powder) was mixed with 50 parts by weight of triacetin. The system was milled in a planetary ball mill (Pulverisette 7, Fritsch) for 12 hours. Milling was performed in cycles of 20 min followed by stopping the mill for 10 min. The rotation speed of the milling disc was 400 rpm. The milling resulted in a white paste. After applying the preparation (32.5 mg) to PMMA 50x50 mm plates with a surface roughness of 5 mM (Schonberg GmbH, Germany), the photoprotective properties of the compound in the range of 290- 400 nm were investigated using an SPF analyzer (SPF-290 AS Analyzer, Solar Light Company). In total, 12 measurements were made (6 for each plate). The value of the SPF i _{n vitro} parameter was 63.14 ± 11.67, UVA PF was 22.40 ± 4.01. c. with a concentration of 75% (w/w)

75 parts by weight of compound 1 (white powder) was mixed with 25 parts by weight of triacetin. The system was milled in a planetary ball mill (Pulverisette 7, Fritsch) for 12 hours. Grinding was performed in cycles of 20 min followed by a stopping the mill for 10 min. The rotation speed of the milling disc was 400 rpm. The milling resulted in a white paste.

2. Preparation of a macrogol cream base

50 parts by weight of polyoxyethylene glycol of molecular weight 400 (PEG 400) was combined with 50 parts by weight of polyoxyethylene glycol of molecular weight of 1500 (PEG 1500) at 70 °C. Thereafter, the homogeneous system was stirred at room temperature until it solidified.

3. Preparation of UV protective creams containing nanostructures of compound 1 Concentrate from point lb was added warm (70 °C) to the macrogol cream base from pt. 2. The concentration of compound 1 in the creams was 12.5% and 5% (w/w). After applying the preparation (32.5 mg) to a 50x50 mm PMMA plate with a surface roughness of 5 mM (Schonberg GmbH, Germany), the photoprotective properties of the compound in the range of 290-400 nm were investigated using an SPF analyzer (SPF-290 AS Analyzer, Solar Light Company). In total, 12 measurements were made (6 for each plate). The recorded values of photoprotective parameters are presented in Table 2.

Table 2. In vitro photoprotective parameters of formulations containing compound 1 at a concentration of 5 and 12.5% (w/w)

The results of the research indicate a high efficiency of absorbing UVB radiation by compound 1. The value of the SPF _{m vitro} factor for the formulation of 12.5% concentration is 14.69 ± 2.25 and exceeds the SPF factor that can be achieved at the maximum concentration allowed for use by a series of UV filters, including octocrylene, octinoxate, 3-(4-methylbenzylidene)camphor, 2- phenyl-lH-benzimidazole-5-sulfonic acid and is comparable to the SPF factor for 2-ethylhexyl triazon photoprotectors [20] Literature:

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