Succinic acid-nicotinamide eutectic crystal as well as preparation method and application thereof

Abstract

The invention discloses a succinic acid-nicotinamide eutectic crystal and a preparation method and application thereof.The molecular formula of the succinic acid-nicotinamide eutectic crystal is C16H18N4O6, the structural formula of the succinic acid-nicotinamide eutectic crystal is shown in the specification, the preparation method comprises the following steps that S1, succinic acid and a solvent are weighed according to the proportion and mixed, and a succinic acid solution is obtained; s2, weighing nicotinamide, adding the nicotinamide into the succinic acid solution, and performing ultrasonic treatment and stirring until the nicotinamide is completely dissolved to obtain a mixed solution; s3, cooling and crystallizing the mixed solution to obtain separated crystals; and S4, filtering the separated crystal by using a Buchner funnel, and drying the solid obtained by filtering in a vacuum drying oven to obtain the succinic acid-nicotinamide eutectic crystal. The invention has the advantages of convenient preparation and relatively low cost, and can be applied to the preparation of personal cleaning products, cosmetics and skin care products with whitening and oil control effects.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of co-crystal preparation, in particular to a succinic acid-nicotinamide co-crystal and a preparation method and application thereof. BACKGROUND

[0002] Nicotinamide (pyridine-3-carboxamide) is widely used in cosmetics. The polarity and hydrophilicity of its amide group (-CONH2) allow nicotinamide to penetrate the stratum corneum barrier and play a "signal regulation" role in cells.

[0003] The unique pyridine ring of nicotinamide can interfere with the lipid synthesis signal pathway in sebaceous gland cells, inhibit the activity of key enzymes (such as phospholipase A2), and reduce the production of triglycerides, cholesterol esters, and other core components of sebum, thereby reducing sebum secretion from the source.

[0004] At the same time, nicotinamide can also alleviate skin redness and sensitivity by regulating the release of inflammatory factors, and help improve the inflammatory problems of acne-prone skin.

[0005] However, this feature also leads to poor stability of nicotinamide. From the environmental factor, ultraviolet light can directly excite electron transition of the pyridine ring, accelerating the destruction of the structure, and high temperature can also increase the molecular motion rate, promoting hydrolysis and oxidation.

[0006] Succinic acid (butanedioic acid, chemical formula C4H6O4) is a common dibasic organic acid that exists widely in living organisms (such as intermediates in the tricarboxylic acid cycle) and has potential activities such as regulating skin metabolism and anti-inflammatory.

[0007] However, the succinic acid molecule contains two hydrophilic carboxyl groups (-COOH), resulting in strong hydrophilicity, which makes it difficult to stay on the skin surface for a long time in rinse-off products, and it is difficult to play a long-acting soothing or oil control effect.

[0008] Supramolecular co-crystal technology can improve the physicochemical properties and efficacy of active ingredients by constructing stable crystal structures through intermolecular non-covalent bonds (hydrogen bonds, van der Waals forces, etc.).

[0009] Currently, although there are studies on the formation of co-crystals of nicotinamide or succinic acid with other substances, there is no related report on the technical scheme of preparing a supramolecular co-crystal with a specific crystal form by process of succinic acid and nicotinamide.

[0010] Therefore, it is of great technical value and application prospect to develop such succinic acid-nicotinamide supramolecular co-crystals. SUMMARY

[0011] The present application aims to provide a succinic acid-nicotinamide co-crystal and a preparation method and application thereof.

[0012] The technical scheme of the present application is as follows:

[0013] A succinic acid-nicotinamide co-crystal, the molecular formula of the succinic acid-nicotinamide co-crystal is C 16 H 18 N4O6, and the structural formula is .

[0014] In the aforementioned succinic acid-nicotinamide co-crystal, the succinic acid-nicotinamide co-crystal is of a triclinic system, a space group P-1, and the succinic acid-nicotinamide co-crystal X-ray powder diffraction pattern has characteristic peaks at 2θ angles of 6.26±0.2°, 17.78±0.2°, 21.91±0.2°, 27.46±0.2°, 30.58±0.2°, 35.92±0.2° and 44.68±0.2°.

[0015] In the aforementioned succinic acid-nicotinamide co-crystal, the succinic acid-nicotinamide co-crystal infrared analysis spectrum has characteristic peaks at 3366 cm -1 ±2cm -1 , 3175 cm -1 ±2cm -1 , 1919 cm -1 ±2cm -1 , 1640 cm -1 ±2cm -1 , 1477 cm -1 ±2cm -1 , 1318 cm - 1 1±2cm -1 , 1111 cm -1 ±2cm -1 .

[0016] A preparation method of a succinic acid-nicotinamide co-crystal, comprising the following steps:

[0017] S1, succinic acid, nicotinamide and solvent are weighed according to the proportion, the succinic acid and the solvent are mixed first, the succinic acid is dissolved in the solvent by continuous stirring to obtain a succinic acid solution;

[0018] S2, the weighed nicotinamide is added to the succinic acid solution, and the solution is ultrasonically treated and stirred until the nicotinamide is completely dissolved to obtain a mixed solution; the solution is completely uniform and stable; the frequency of the ultrasonic instrument is 60 kHz, the ultrasonic temperature is 35-55℃, the ultrasonic time is 20-60 min, and the solution is stirred for 2-4 h after the ultrasonic treatment.

[0019] S3, cooling the mixed solution to obtain precipitated crystals;

[0020] S4, filtering the precipitated crystals with a Buchner funnel, and drying the obtained solid in a vacuum drying oven to obtain succinic acid-nicotinamide eutectic crystals.

[0021] In the aforementioned method for preparing succinic acid-nicotinamide eutectic crystals, the molar ratio of succinic acid to nicotinamide is (1-2):(1-3).

[0022] In the aforementioned method for preparing succinic acid-nicotinamide eutectic crystals, in step S1, the mass ratio of the sum of the mass of succinic acid and nicotinamide to the mass of the solvent is 1:(5-15).

[0023] In the aforementioned method for preparing succinic acid-nicotinamide eutectic crystals, limiting the premix and the dissolution conditions to the range helps to improve the dissolution and mixing efficiency of the premix, so that succinic acid and nicotinamide can be more efficient and more thorough reaction.

[0024] In the aforementioned method for preparing succinic acid-nicotinamide eutectic crystals, in step S1, the solvent is one or more of water, methanol, ethanol, acetonitrile, ethyl acetate, acetone, isopropanol, acetonitrile, dichloromethane.

[0025] In the aforementioned method for preparing succinic acid-nicotinamide eutectic crystals, step S3, the mixed solution is cooled to obtain precipitated crystals, and the specific content is as follows:

[0026] S3.1, pre-cooling and crystal nucleus formation stage: place the sample in a low-temperature environment close to the freezing point (for example, about 4°C), and store for 2-4 hours;

[0027] S3.2, shallow freezing and crystal growth stage: transfer the sample to a shallow freezing environment (for example, about -10°C), and store for 2-4 hours;

[0028] S3.3, deep freezing and structure stabilization stage: place the sample in a deep freezing environment (for example, about -20°C), and store for 24-36 hours.

[0029] In the aforementioned method for preparing succinic acid-nicotinamide eutectic crystals, the crystallization solution is first stirred at a higher temperature until it is completely uniform, and then sequentially passes through multiple set temperature zones, maintaining a constant temperature between each temperature zone for a period of time, so that the system gradually reaches a new dissolution equilibrium; under the action of temperature gradient, the weak interaction between solute molecules (including hydrogen bond, ion-dipole, π-π stacking, etc.) can be fully rearranged in a longer nucleation time, promoting the formation of target supramolecular ordered structure and inhibiting the generation of impurities or by-product crystals.

[0030] In the aforementioned preparation method of the succinic acid-nicotinamide co-crystal, the drying temperature of the vacuum drying oven in step S4 is 25-35 DEG C, and the drying time is 18-36h.

[0031] The vacuum degree is -0.06--0.095 MPa.

[0032] The temperature rising rate in the drying oven can be controlled as 0.5-2 DEG C / min during the drying process, and inert gas (such as nitrogen or argon) can be optionally filled to reduce oxidation or decomposition.

[0033] The drying conditions are maintained under the above conditions, which can better maintain the original characteristics of the material during the drying process.

[0034] The succinic acid-nicotinamide co-crystal is applied to the preparation of personal cleaning products, cosmetics and skin care products.

[0035] Compared with the prior art, the present application has the following beneficial effects:

[0036] 1) The preparation method of the succinic acid-nicotinamide co-crystal can prepare the succinic acid-nicotinamide co-crystal with high stability, and has the advantages of simple operation, high product yield and low production cost, which is beneficial to large-scale popularization and application.

[0037] The operation is simple, the ultrasonic assisted dissolution is accompanied by stirring, which can make the succinic acid and nicotinamide react more efficiently and more completely without high temperature.

[0038] The product yield can reach 78%, and the solvent can be reused, and after cooling and crystallization, it can be dissolved and crystallized again without affecting the purity.

[0039] 2) The succinic acid-nicotinamide co-crystal prepared by the present application has no irritation compared with single succinic acid and nicotinamide, and has mild properties, and the succinic acid-nicotinamide co-crystal can improve the poor stability of nicotinamide.

[0040] 3) The succinic acid-nicotinamide co-crystal prepared by the present application can significantly improve the residual effect of succinic acid on the human body surface, can improve the bioavailability in personal cleaning products, cosmetics and skin care products, and can better play its efficacy.

[0041] Therefore, the present application has the advantages of convenient preparation, relatively low cost and application in the preparation of personal cleaning products, cosmetics and skin care products with whitening and oil control effects. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 XRD comparison chart of succinic acid-nicotinamide co-crystal, monomer and physical mixture in experiment 1;

[0043] Figure 2The infrared contrast chart of succinic acid-nicotinamide co-crystal, monomer and physical mixture in experiment 2 is shown in the following figure:

[0044] Figure 3 The thermogravimetric analysis contrast chart of succinic acid-nicotinamide co-crystal and succinic acid monomer in experiment 3 is shown in the following figure:

[0045] Figure 4 The XRD contrast chart of succinic acid-nicotinamide co-crystal obtained by adding different proportions of succinic acid and nicotinamide in the present application is shown in the following figure:

[0046] Figure 5 The degradation chart of nicotinamide in experiment 4 is shown in the following figure: Figure 6 The degradation chart of succinic acid-nicotinamide co-crystal in experiment 4 is shown in the following figure: Figure 7 The degradation improvement chart of nicotinamide in experiment 4 is shown in the following figure:

[0047] Figure 8 The cell survival rate result chart of succinic acid under different concentrations in experiment 5 is shown in the following figure:

[0048] Figure 9 The cell survival rate result chart of nicotinamide under different concentrations in experiment 5 is shown in the following figure:

[0049] Figure 10 The cell survival rate result chart of physical mixture of succinic acid and nicotinamide under different concentrations in experiment 5 is shown in the following figure:

[0050] Figure 11 The cell survival rate result chart of succinic acid-nicotinamide co-crystal obtained by example 1 under different concentrations in experiment 5 is shown in the following figure:

[0051] Figure 12 The inhibition effect contrast chart of oil in experiment 6 is shown in the following figure. DETAILED DESCRIPTION

[0052] The present application will be further described below in combination with the drawings and examples, but it is not taken as the basis for limiting the present application.

[0053] Example 1. A preparation method of succinic acid-nicotinamide co-crystal, the steps are as follows:

[0054] S1, 1.77g of succinic acid is mixed with 20g of anhydrous ethanol and 20g of isopropyl alcohol, and the succinic acid is dissolved in the solution by continuous stirring to form a succinic acid solution;

[0055] S2, 3.66g of nicotinamide is weighed and added to the succinic acid solution in S1, the frequency of the ultrasonic instrument is 60kHz, the ultrasonic temperature is 35℃, the ultrasonic time is 20min, and after the ultrasonic is finished, it is stirred at 35℃ for 4h; a uniform succinic acid and nicotinamide mixed solution is obtained.

[0056] S3, the mixed solution in S2 is cooled to crystallize to obtain precipitated crystals; the crystallization conditions are that, after completion of stirring, it is first stored at 4°C for 2h, then transferred to -10°C for 2h, and then transferred to -20°C for 24h;

[0057] S4, the precipitate in S3 is filtered with a Buchner funnel, and the obtained solid is placed in a vacuum drying box at 25°C for drying for 24h to obtain succinic acid-nicotinamide cocrystals; the vacuum degree of the drying box is -0.06MPa.

[0058] After testing, the mass of the product succinic acid-nicotinamide cocrystals is 4.27g, and the calculated yield is 78.64%; at the same time, the melting point of the product is 150.4°C, and the decomposition temperature is 249.8°C (the decomposition temperature of succinic acid is 237.9°C, and the decomposition temperature of nicotinamide is 128-131°C), indicating that high-purity succinic acid-nicotinamide cocrystals are prepared.

[0059] The molecular formula of the succinic acid-nicotinamide cocrystals is C 16 H 18 N4O6, and the structural formula is .

[0060] Succinic acid and nicotinamide form cocrystals in a molar ratio of 1:2, wherein the carboxyl group of succinic acid can provide O-H…O type hydrogen bonds and also act as a carbonyl acceptor; at the same time, the amide group of nicotinamide provides both N-H hydrogen donor sites and C=O hydrogen acceptor sites, so that the two form a strong and directional "double-point pairing" hydrogen bond network;

[0061] This complementary hydrogen bond-driven spontaneous assembly does not involve covalent bond formation, but is a typical supramolecular self-organization process; specifically, the double hydrogen bond complementary interaction between carboxylic acid (-COOH) and amide (-CONH2) spontaneously assembles into a stable supramolecular structure;

[0062] The two carboxyl groups at both ends of succinic acid form hydrogen bonds with two nicotinamide molecules, and each nicotinamide molecule can also form hydrogen bonds with two succinic acid molecules; these hydrogen bonds together form a hydrogen bond network, and succinic acid and nicotinamide in a molar ratio of 1:2 form a three-dimensionally ordered crystal structure through these hydrogen bonds, obtaining succinic acid-nicotinamide cocrystals with a crystal structure different from that of succinic acid;

[0063] After succinic acid and nicotinamide form cocrystals, the electron cloud is redistributed to reduce the irritability, and at the same time, the cocrystals also have excellent liposolubility to improve the efficacy.

[0064] Nicotinamide, as the active form of vitamin B3, is a white crystalline powder without obvious odor, with a molecular formula of C6H6N2O and a molecular weight of 122.13, and a melting point of about 128-131℃; it has strong water and ethanol solubility, and has weak alkalinity and weak acidity, and can be hydrolyzed to form nicotinic acid under acidic or basic conditions due to the amide structure contained therein;

[0065] The core advantage is high biological activity, which can directly participate in human metabolism and maintain cell health, and has high safety. Forming a co-crystal with succinic acid is beneficial to reducing the irritability of succinic acid and improving the stability of itself.

[0066] The application of a succinic acid-nicotinamide co-crystal in the preparation of personal cleaning products, cosmetics and skin care products.

[0067] Example 2. A preparation method of a succinic acid-nicotinamide co-crystal, comprising the following steps:

[0068] S1, 2.36g of succinic acid is mixed with 45g of anhydrous ethanol and 45g of isopropyl alcohol, and the succinic acid is continuously stirred to dissolve in the solution to form a succinic acid solution;

[0069] S2, 2.44g of nicotinamide is weighed and added to the succinic acid solution in S1, the frequency of the ultrasonic instrument is 60kHz, the ultrasonic temperature is 45℃, and the ultrasonic time is 60min, and after ultrasonic is completed, stirring is carried out at 45℃ for 4h; a uniform succinic acid and nicotinamide mixed solution is obtained.

[0070] S3, the mixed solution in S2 is cooled to crystallize to obtain the precipitated crystals; the crystallization conditions are that after the stirring is completed, it is first placed at 4℃ for 3h, then transferred to-10℃ for 3h, and then transferred to-20℃ for 30h;

[0071] S4, the precipitate in S3 is filtered with a Buchner funnel, the obtained solid is placed in a 25℃ vacuum drying box for drying for 24h, and a succinic acid-nicotinamide co-crystal is obtained; the vacuum degree of the drying box is-0.095MPa.

[0072] After testing, the mass of the product succinic acid-nicotinamide co-crystal is 3.61g, and the calculated yield is 75.21%; at the same time, the melting point of the product is 150.4℃, and the decomposition temperature is 249.8℃, indicating that a high-purity succinic acid-nicotinamide co-crystal is prepared.

[0073] Example 3. A preparation method of a succinic acid-nicotinamide co-crystal, comprising the following steps:

[0074] S1, 7.08g of succinic acid is mixed with 35g of anhydrous ethanol and 35g of isopropyl alcohol, and the succinic acid is continuously stirred to dissolve in the solution to form a succinic acid solution;

[0075] S2. Weigh 1.83g of nicotinamide and add it to the succinic acid solution in S1. The frequency of the ultrasonic instrument is 60kHz, the ultrasonic temperature is 55℃, and the ultrasonic time is 60min. After ultrasonication, stir at 45℃ for 4h to obtain a homogeneous mixed solution of succinic acid and nicotinamide.

[0076] S3. Cool the mixed solution in S2 to crystallize and obtain the precipitated crystals. The crystallization conditions are as follows: after stirring, it should first be stored at 4℃ for 4 hours, then transferred to -10℃ for 4 hours, and then transferred to -20℃ for 36 hours.

[0077] S4. Filter the precipitate from S3 using a Buchner funnel, and dry the resulting solid in a vacuum drying oven at 35°C for 24 hours to obtain succinic acid-nicotinamide eutectic; the vacuum degree of the drying oven is -0.095MPa.

[0078] After testing, the mass of the succinic acid-nicotinamide cocrystal was 4.89 g, and the yield was calculated to be 81.23%. At the same time, the melting point of the product was measured to be 150.4℃ and the decomposition temperature was 249.8℃, indicating that a high-purity succinic acid-nicotinamide cocrystal was prepared.

[0079] Example 4. A method for preparing a succinic acid-nicotinamide eutectic, comprising the following steps:

[0080] S1. Mix 1.18g of succinic acid with 20g of anhydrous ethanol and 15g of isopropanol, and stir continuously to dissolve the succinic acid in the solution to form a succinic acid solution.

[0081] S2. Weigh 3.66g of nicotinamide and add it to the succinic acid solution in S1. The frequency of the ultrasonic instrument is 60 kHz, the ultrasonic temperature is 45℃, and the ultrasonic time is 60 min. After ultrasonication, stir at 45℃ for 2 h to obtain a homogeneous mixed solution of succinic acid and nicotinamide.

[0082] S3. Cool the mixed solution in S2 to crystallize and obtain the precipitated crystals. The crystallization conditions are as follows: after stirring, it should first be placed at 4℃ for 4 hours, then transferred to -10℃ for 4 hours, and then transferred to -20℃ for 24 hours.

[0083] S4. Filter the precipitate from S3 using a Buchner funnel, and dry the resulting solid in a vacuum drying oven at 30°C for 24 hours to obtain succinic acid-nicotinamide eutectic; the vacuum degree of the drying oven is -0.06MPa.

[0084] The mass of the succinic acid-nicotinamide cocrystal was 3.61 g, and the yield was calculated to be 74.59%. The melting point of the product was 150.4℃ and the decomposition temperature was 249.8℃, indicating that a high-purity succinic acid-nicotinamide cocrystal was prepared.

[0085] The research found that the molar ratio of succinic acid-nicotinamide co-crystal in (1-2): (1-3) conditions can form stable co-crystals, and the XRD spectrum peak position and peak intensity are basically the same, as shown in the results. Figure 4

[0086] Comparative Example

[0087] Comparative Example 1:

[0088] Similar to Example 1, the only difference is that in step S3, there is no gradient cooling;

[0089] After testing, the mass of the product is 2.21 g, and the calculated yield is 40.70%, with very low yield.

[0090] Comparative Example 2:

[0091] Similar to Example 1, the only difference is that in S1 and S2, 1.18 g of succinic acid and 4.88 g of nicotinamide and 40 g of ethanol are mixed, i.e. the molar ratio of succinic acid to nicotinamide is 1:4, to obtain a premix;

[0092] After testing, the mass of the product is 3.28 g, and the calculated yield is 54.13%; at the same time, it is measured that the product is multi-stage decomposition and the decomposition temperatures are 150.5°C and 249.8°C respectively, indicating that the product prepared is a mixture.

[0093] Comparative Example 3:

[0094] Similar to Example 1, the only difference is that in step S2, only ultrasonic is used without stirring before cooling crystallization;

[0095] After testing, the mass of the product is 2.35 g, and the calculated yield is 43.28%, with very low yield.

[0096] Comparative Example 4:

[0097] Similar to Example 1, the only difference is that in steps S1 and S2, 1.77 g of succinic acid and 3.66 g of nicotinamide and 50 g of ethanol and 50 g of isopropanol are mixed, i.e. the molar ratio of succinic acid to nicotinamide is 1:2, to obtain a premix;

[0098] No crystals are precipitated after gradient cooling, which is speculated to be due to too much solvent, which cannot form a supramolecule.

[0099] Comparative Example 5:

[0100] Similar to Example 1, the only difference is that in step S4, heating drying is used with a heating temperature of 85°C;

[0101] ​XRD results found that the heating dried supramolecular pattern compared to vacuum drying more miscellaneous peaks, speculated that the product purity is not high.

[0102] Verification experiment

[0103] The structure characterization, physicochemical properties and biological activity of succinic acid-nicotinamide co-crystal were verified by experiment.

[0104] Experiment 1 X-ray powder diffraction (XRD) test

[0105] Instrument and parameters: X-ray diffractometer model D8 ADVANCE Da Vinci; voltage setting is 30kV, current is 20mA, scanning range 5-45°; scanning speed 5° / min;

[0106] Test method: powder X-ray diffraction test was carried out on succinic acid, nicotinamide, physical mixture of succinic acid and nicotinamide, and supramolecular succinic acid-nicotinamide co-crystal prepared in Example 1, respectively, and then the data results of each sample were compared and analyzed;

[0107] As shown in the accompanying Figure 1 , after physical mixing of succinic acid and nicotinamide in proportion, the XRD spectrum showed that the monomer peaks of succinic acid and nicotinamide were superimposed, and after the formation of supramolecule, the characteristic peaks of monomer were weakened or disappeared to a certain extent, and new characteristic peaks appeared at 6.26±0.2°, 17.78±0.2°, 21.91±0.2°, 27.46±0.2°, 30.58±0.2°, 35.92±0.2° and 44.68±0.2°, indicating that different from monomer, a crystal form substance was produced during the reaction of succinic acid and nicotinamide, indicating that succinic acid-nicotinamide co-crystal was successfully prepared.

[0108] Experiment 2 infrared spectroscopy characterization

[0109] Test method: infrared spectroscopy characterization was carried out on succinic acid, nicotinamide and succinic acid-nicotinamide co-crystal obtained in Example 1, wherein the test parameter was transmittance, the test wave number was 500cm -1 -4000cm -1 , the resolution was 0.2cm -1 , and the test mode was tablet pressing;

[0110] As Figure 2 , succinic acid has multiple stretching vibration peaks at 2500-3300cm -1 , and nicotinamide has stretching vibration peaks at 3356cm -1 , 3115cm -1 , after the reaction of the two, the stretching vibration peaks shift to 3366cm -1, 3175 cm -1 At this point, the peak is broadened and shifted to low frequency due to the formation of N-H···O hydrogen bond between the amide N-H and the carboxylic O-H, indicating that succinic acid reacts with nicotinamide to form a co-crystal, which is a new structure.

[0111] Experiment 3 Thermal analysis (TG-DSC) test

[0112] Test method: thermal analysis (TG-DSC) test was performed on succinic acid and the succinic acid-nicotinamide co-crystal prepared in Example 1;

[0113] TG test was performed using Netzsch TG 209F3 equipment, 5-10 mg of sample was placed in an alumina crucible, the heating rate was 10°C / min, the test temperature range was 30-400°C, and the sweeping gas and protective gas were nitrogen;

[0114] DSC test was performed using Netzsch DSC 200F3 equipment, the sample was placed in an alumina crucible, covered with a hole, the heating rate was 10°C / min to the set temperature, the test temperature range was 30-300°C, and the sweeping gas and protective gas were nitrogen;

[0115] As Figure 3 (thermogravimetric data in red and differential thermal data in black), the DSC curve of succinic acid (SA) has a melting point at 195.6°C and a boiling point at 237.9°C; the TGA curve has only one weight loss platform corresponding to the evaporation of succinic acid;

[0116] The first endothermic peak of the DSC curve of the succinic acid-nicotinamide co-crystal (SA-NIC) is at 150.4°C, which is between nicotinamide (128-131°C) and succinic acid (195.6°C), indicating the formation of a new substance; the TGA curve has only one weight loss platform, indicating that the purity of the product may be high.

[0117] Experiment 4 Stability test of succinic acid-nicotinamide co-crystal

[0118] Test method: ultraviolet spectrophotometry was used to investigate the stability of nicotinamide and the succinic acid-nicotinamide co-crystal prepared in Example 1;

[0119] The characteristic ultraviolet absorption peak of nicotinamide was used as the detection basis, the detection wavelength of nicotinamide was set at 262 nm, and the absorption peak of supramolecular nicotinamide was blue-shifted due to hydrogen bonding, so the detection wavelength was adjusted to 255-258 nm (the actual detection wavelength was the wavelength corresponding to the maximum absorption peak);

[0120] A series of concentrations of nicotinamide standard solution were prepared, and the absorbance was measured at the corresponding detection wavelength, and the standard curve was drawn and the concentration-absorbance linear regression equation was established;

[0121] The nicotinamide and supramolecular nicotinamide samples were placed under the set test conditions (-20°C, 25°C, 45°C, light, cycle) for stability investigation, and samples were taken periodically (1 week, 2 weeks, 4 weeks) and the absorbance was measured at the corresponding detection wavelength, and the actual content of nicotinamide in the sample was calculated by the standard curve regression equation, and the content changes at different time points were compared to judge the decomposition and stability difference of the sample;

[0122] As shown in Figures 5-7 , the degradation rate of nicotinamide gradually increased with time under different conditions, and the higher the temperature, the faster the degradation under light and cycle conditions; while the degradation rate of succinic acid-nicotinamide co-crystal was significantly lower than that of nicotinamide, especially under 45°C, light and cycle conditions, it showed better stability;

[0123] Further data on degradation improvement rate showed that succinic acid-nicotinamide co-crystal could effectively inhibit the degradation of nicotinamide under -20°C, 25°C, 45°C, light and cycle conditions, and the improvement effect was most prominent at 45°C, which fully explained that succinic acid-nicotinamide co-crystal could significantly improve the stability of nicotinamide, and the advantage was more obvious under harsh conditions such as high temperature and light, and the high temperature degradation improvement rate could reach 30%.

[0124] Experiment 5 Safety test of succinic acid-nicotinamide co-crystal

[0125] 1. Experimental principle

[0126] The CCK-8 (Cell Counting Kit-8) detection method is based on the positive correlation between cell metabolic activity and cell number, and the quantitative evaluation of active substance safety is realized by measuring the dehydrogenase activity in cells. The specific method is as follows:

[0127] Human keratinocytes HaCaT were inoculated in 96-well plates, and after culture to the logarithmic growth phase, different concentrations of active substances (succinic acid-nicotinamide co-crystal, succinic acid monomer, nicotinamide monomer, physical mixture of succinic acid + nicotinamide) were added to the culture medium, and blank control group (no cells + culture medium) and negative control group (cells + culture medium without active substances) were set up, and each group had 3-6 replicate wells; After incubation at 37°C, 5% CO2 incubator overnight, 10μL CCK-8 reagent was added to each well, and incubation was continued for 1-4h, so that water-soluble tetrazolium salt (WST-8) in the reagent was reduced to orange formazan dye by intracellular dehydrogenase;

[0128] After 24h of sample addition and culture, the supernatant was discarded, and 100μl of 10% CCK-8 solution was added to each well. Incubate at 37°C for 1h in the dark, and after incubation, read the OD value at 490nm;

[0129] The cell survival rate was calculated according to the formula,

[0130] (OD value of experimental group - OD value of blank control group) / (OD value of negative control group - OD value of blank control group) x 100%,

[0131] The cytotoxicity of the active substance is determined by the survival rate curve. If the survival rate is ≥80%, it is generally considered that the active substance has no obvious toxicity to the cells at this concentration, and the feasibility of the application of the active substance within the safe concentration range is further evaluated.

[0132] In the test, the safety of succinic acid monomer, nicotinamide monomer, succinic acid + nicotinamide physical mixture sample and succinic acid-nicotinamide co-crystal prepared in Example 1 was tested;

[0133] Four groups of samples were selected at a concentration of 0.1-1% for HaCaT cell experiments; the test groups were set as: blank control group, sample group, and the specific grouping is shown in Table 1.

[0134]

[0135] Test results:

[0136] Specifically, the test results of succinic acid, nicotinamide, succinic acid + nicotinamide (physical mixture), and succinic acid-nicotinamide co-crystal are respectively shown in Tables 2, 3, 4 and 5.

[0137]

[0138]

[0139]

[0140]

[0141] As shown in Tables 2-5 and Figures 8-11 The toxicity test results prove that:

[0142] Succinic acid has no toxicity to human immortalized keratinocytes when the concentration is <0.1%;

[0143] Nicotinamide has almost no toxicity to human immortalized keratinocytes when the concentration is 0-0.2%;

[0144] Succinic acid-nicotinamide co-crystal and succinic acid + nicotinamide (physical mixture) have no toxicity to human immortalized keratinocytes when the concentration is ≤0.25%. At the same concentration (0.25%), the cell survival rate of the succinic acid-nicotinamide co-crystal group is higher than that of the succinic acid + nicotinamide (physical mixture) group.

[0145] In summary, in terms of mildness, succinic acid-nicotinamide co-crystal > succinic acid + nicotinamide (physical mixture) > nicotinamide > succinic acid, indicating that the formation of a co-crystal of succinic acid and nicotinamide improves the mildness of succinic acid and nicotinamide, and is superior to the physical mixture of succinic acid and nicotinamide.

[0146] Experiment 6: Oil control performance test

[0147] 1. Experimental principle

[0148] Nile Red staining is a fluorescence staining technique commonly used to assess oil content, and has important applications in the evaluation of oil control effects of cosmetics (such as skin care products);

[0149] Using the specific binding properties of Nile Red and oil, the change in oil content can be reflected by the intensity of the fluorescence signal, thereby judging the effect of oil control products;

[0150] Nile Red is a lipophilic fluorescent dye, and its molecular structure has strong fat solubility. In oil, Nile Red will emit strong fluorescence (maximum excitation wavelength about 550 nm, emission wavelength about 630 nm, red fluorescence); In water or polar solvents, its fluorescence intensity decreases significantly (almost no light);

[0151] Nile Red is embedded in the hydrophobic structure of oil (such as triglyceride, fatty acid, sebum, etc.) through hydrophobic interaction, forming a stable combination, thereby showing obvious fluorescence signal under fluorescence microscope or fluorescence spectrophotometer;

[0152] The fluorescence intensity emitted by Nile Red after binding with oil is positively correlated with the oil content in the sample. If there are obvious red areas in the cells, it means that there is lipid, and the deeper the color, the higher the relative lipid content.

[0153] 2. Instruments and equipment

[0154] Super-clean workbench, carbon dioxide incubator, fluorescence microscope, centrifuge, cell counting plate and cell culture dish.

[0155] 3. Reagents and materials

[0156] Cell material: human sebaceous gland cells SZ95;

[0157] Reagents: DMEM high-sugar culture solution (without pyruvic acid), fetal bovine serum, double antibody, PBS, trypsin, isovaleric acid, finasteride, Nile Red dye, FDA dye.

[0158] 4. Test process

[0159] 4.1 Pre-treatment and test grouping of test substances

[0160] 4.1.1 Cell plating

[0161] After cell counting, dilute to the desired concentration, add cell suspension in cell culture plates so that the culture medium volume is 1 mL / well, and the number of living cells is 5 x 10 4 cells / well;

[0162] 4.1.2 Sample loading process

[0163] After 24 h of plating, the cell fusion rate was 40-60%, different concentrations of test substances were added to make the concentration of the test concentration, and 3 parallel test wells were set up, and the cells were cultured for another 24 h. The specific test substance concentration is shown in Table 6.

[0164]

[0165] 4.1.3 Nile red staining

[0166] Rinse: discard the culture medium and wash with PBS 3 times;

[0167] Fix: add 4% paraformaldehyde (300 μL) for 30 min;

[0168] Staining: prepare Nile red staining solution (working concentration 10 μg / mL), discard the fixing solution, rinse the cells with PBS 3 times, add Nile red staining solution (300 μL) for 15 min;

[0169] Photograph: under an inverted fluorescence microscope, observe the staining of cells in each group and take pictures;

[0170] Result analysis: use image analysis software to quantitatively analyze the fluorescence intensity.

[0171] 5. Test results

[0172] As Figure 12 , the IOD value of the LA group was significantly higher than that of the BC group, indicating that the experimental model was effective;

[0173] The fluorescence intensity of different concentrations (500 ppm, 1000 ppm) of nicotinamide, succinic acid, succinic acid-nicotinamide co-crystal, and physical mixture of succinic acid + nicotinamide was significantly lower than that of the LA group, indicating that these samples all had an oil control effect.

[0174] Further comparison of the differences between groups showed that the fluorescence intensity values of succinic acid-nicotinamide co-crystal and physical mixture of succinic acid + nicotinamide at different concentrations were lower, and the oil control effect of succinic acid-nicotinamide co-crystal was particularly outstanding.

[0175] Conclusion: Nicotinamide, succinic acid, succinic acid-nicotinamide co-crystal and physical mixture of succinic acid and nicotinamide all have oil control effect, and the oil control effect of the supermolecular form of succinic acid-nicotinamide co-crystal is better, suggesting that the oil control performance can be effectively enhanced through supermolecular technology, and a scientific basis is provided for the formula development of oil control skin care, cosmetic or personal cleansing products.

[0176] As known in the art, nicotinamide as a classic whitening active can achieve skin lightening effect by inhibiting melanin transport, and succinic acid can synergistically enhance skin metabolic efficiency to assist whitening;

[0177] From the mechanism, the supermolecular succinic acid-nicotinamide co-crystal improves the stability of nicotinamide by forming a stable complex structure through non-covalent interaction, while the efficacy of the active is not weakened;

[0178] At the same time, the succinic acid group may provide auxiliary effect in local microenvironment regulation, thus theoretically endowing the complex with potential application value in the direction of skin color uniformization and brightness improvement.

Claims

1. A succinic acid-nicotinamide eutectic, characterized in that: The molecular formula of the succinic acid-nicotinamide cocrystal is C 16 H 18 N4O6, structural formula is .

2. The succinic acid-nicotinamide eutectic according to claim 1, characterized in that: The succinic acid-nicotinamide eutectic is a triclinic crystal with space group P-1. The X-ray powder diffraction pattern of the succinic acid-nicotinamide eutectic exhibits characteristic peaks at 2θ angles of 6.26±0.2°, 17.78±0.2°, 21.91±0.2°, 27.46±0.2°, 30.58±0.2°, 35.92±0.2°, and 44.68±0.2°.

3. The succinic acid-nicotinamide eutectic according to claim 1, characterized in that: The infrared spectrum of the succinic acid-nicotinamide cocrystal was at 3366 cm⁻¹. -1 ±2cm -1 3175cm -1 ±2cm -1 1919 cm -1 ±2cm -1 1640 cm -1 ±2cm -1 1477 cm -1 ±2cm -1 1318 cm -1 1±2cm -1 1111 cm -1 ±2cm -1 Each location exhibits a characteristic peak.

4. The method for preparing a succinic acid-nicotinamide co-crystal according to any one of claims 1-3, characterized in that, Includes the following steps: S1. Weigh out succinic acid, nicotinamide and solvent according to the ratio. First mix succinic acid and solvent, and continue stirring to dissolve succinic acid in solvent to obtain succinic acid solution. S2. Add the weighed nicotinamide to the succinic acid solution, sonicate and stir until the nicotinamide is completely dissolved to obtain a mixed solution; the sonication temperature is 35-55℃, the sonication time is 20-60min, and the solution is stirred for 2-4h after sonication. S3. Cool the mixed solution to crystallize and obtain the precipitated crystals; S4. Filter the precipitated crystals using a Buchner funnel, and dry the resulting solid in a vacuum drying oven to obtain succinic acid-nicotinamide eutectic.

5. The method for preparing succinic acid-nicotinamide eutectic according to claim 4, characterized in that: The molar ratio of succinic acid to nicotinamide is (1-2):(1-3).

6. The method for preparing succinic acid-nicotinamide eutectic according to claim 4, characterized in that: In step S1, the mass ratio of the sum of the masses of succinic acid and nicotinamide to the mass of the solvent is 1:(5-15).

7. The method for preparing succinic acid-nicotinamide eutectic according to claim 4, characterized in that: In step S1, the solvent is one or more of water, methanol, ethanol, acetonitrile, ethyl acetate, acetone, isopropanol, acetonitrile, and dichloromethane.

8. The method for preparing succinic acid-nicotinamide eutectic according to claim 4, characterized in that, Step S3, which involves cooling the mixed solution to crystallize and obtain the precipitated crystals, is detailed below: S3.1 Pre-cooling and crystal nucleation stage: Place the sample in a low-temperature environment near the freezing point and store for 2-4 hours; S3.2, Shallow freezing and crystal growth stage: Transfer the sample to a shallow freezing environment and store for 2-4 hours; S3.3 Deep Freezing and Structural Stabilization Stage: Place the sample in a deep freezing environment and preserve it for 24-36 hours.

9. The method for preparing succinic acid-nicotinamide eutectic according to claim 4, characterized in that: The drying temperature in the vacuum drying oven in step S4 is 25-35℃, and the drying time is 18-36h.

10. The use of a succinic acid-nicotinamide eutectic according to any one of claims 1-3 in the preparation of personal care products, cosmetics and skin care products.

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