An ectoine-malic acid supramolecular complex and a preparation method thereof

Abstract

The application discloses an ectoine-malic acid supramolecular complex and a preparation method thereof, and belongs to the technical field of cosmetics. The technical problem to be solved is that malic acid has strong irritation when used as a cosmetic raw material. The technical solution is that the ectoine-malic acid supramolecular complex is formed by the intermolecular hydrogen bond interaction between malic acid and ectoine; the malic acid is wrapped in a binary hydrogen bond network, the release rate is controlled, the free acid concentration is reduced, and the problem of reducing the irritation of malic acid is solved.

Description

Technical Field

[0001] This invention belongs to the field of cosmetic technology, specifically relating to an ectoine-malic acid supramolecular complex and its preparation method. Background Technology

[0002] Malic acid is a widely used fruit acid ingredient in cosmetics. It belongs to the alpha-hydroxy acid (AHA) class and is abundant in fruits such as apples. Fruit acids promote the shedding of dead skin cells by weakening the ionic bonds between desmosomes in keratinocytes. Simultaneously, they stimulate dermal fibroblasts to synthesize collagen and glycosaminoglycans, achieving multiple benefits including exfoliation, brightening skin tone, improving clogged pores, and anti-aging. It is widely used in serums, creams, masks, and skin-renewing products.

[0003] However, malic acid has significant drawbacks while delivering its benefits. Because it works by exfoliating the skin, it can easily cause discomfort such as stinging, redness, and burning sensations. In severe cases, it can lead to dermatitis, flushing, peeling, and edema, especially in people with sensitive skin. The China Pharmaceutical Information Query Platform explicitly states that malic acid accelerates the removal of dead skin cells, affecting the skin barrier structure, and is not recommended for people with sensitive skin or facial redness.

[0004] Meanwhile, according to the "Cosmetic Safety Technical Specifications," the total content of α-hydroxy acids (including malic acid) and their salts and esters in cosmetics must not exceed 6.0%, and the product's pH value must not be lower than 3.5. These dual restrictions on concentration and pH limit the scope of formulation design and constrain the effectiveness of the product.

[0005] Ectoine is a natural cyclic amino acid derivative with functions such as moisturizing, anti-inflammatory, stabilizing biological membranes, and protecting protein structure. While there are existing reports of simple combinations of malic acid and ectoine, such simple physical mixing cannot form stable interactions at the molecular level, and the irritant properties of malic acid remain.

[0006] Relevant patent documents retrieved: This document, published in China (CN115363978A) on July 9, 2024, discloses a composition and skincare product for improving rosacea. Its active ingredients are ectoine and organic acids (including fruit acids such as malic acid). Through the combination of ectoine and extremely low concentrations of organic acids, it promotes the proliferation of human keratinocytes and accelerates the thickening of the stratum corneum, thereby improving rosacea and overcoming the technical prejudice that organic acids are unsuitable for skin with rosacea. While this document represents the closest prior art to this invention, the ectoine and organic acids in this document are a simple physical mixture; a stable supramolecular structure is not formed between them, and the irritation problem of the organic acids is not fundamentally solved.

[0007] This document, published in China (CN117442508A) on March 11, 2025, discloses a soluble azelaic acid supramolecular complex system with soothing effects. The system comprises azelaic acid, ectoine, and panthenol, which form a supramolecular structure via hydrogen bonds, improving the water solubility of azelaic acid and reducing its irritant properties. The document confirms that ectoine can form supramolecular systems with organic acids via hydrogen bonds, but its core components are azelaic acid and panthenol; it does not involve a binary supramolecular complex of malic acid and ectoine. Azelaic acid and malic acid have significantly different molecular structures—azelaic acid is a straight-chain dicarboxylic acid, while malic acid is a hydroxyl-containing dicarboxylic acid. The number and type of hydrogen bond donor sites differ between the two, resulting in a fundamental difference in the way they form supramolecular structures and the properties of their complexes.

[0008] The document published in China, with publication number CN119822952A and publication date of April 15, 2025, discloses a ferulic acid-ectoine supramolecular cocrystal, its preparation method, and its applications. The cocrystal is formed by ferulic acid and ectoine through hydrogen bonding, increasing the solubility of ferulic acid by more than 3.8 times and achieving synergistic antioxidant and soothing effects. However, this method addresses the low solubility of ferulic acid, which differs from the technical objective of this application in solving the irritation problem of malic acid. Furthermore, malic acid and ferulic acid have significantly different molecular structures and physicochemical properties, making simple analogy inappropriate.

[0009] The prior art represented by the aforementioned documents has at least the following unresolved technical problems or defects: Currently, the combination of malic acid and ectoine only reaches the level of simple physical mixing and fails to form a stable complex structure at the molecular level, thus failing to fundamentally solve the irritant problem of malic acid. Therefore, there is an urgent need to develop a new technological solution that can form a stable complex structure through intermolecular interactions to reduce the irritant effect of malic acid. Summary of the Invention

[0010] The purpose of this invention is to provide: An ectoine-malic acid supramolecular complex and its preparation method are disclosed to address the technical problem of strong irritation when malic acid is used as a cosmetic ingredient in the prior art, or a combination thereof.

[0011] Terminology Explanation: Unless otherwise defined, all technical terms in this document have the same meanings as commonly understood by one of ordinary skill in the art to which the subject matter of the claims pertains. Unless otherwise stated, all patents, patent inventions, and publications cited in this document are incorporated herein by reference in their entirety. If multiple definitions exist for terms in this document, the definitions in this chapter shall prevail.

[0012] It should be understood that the above brief description and the following detailed description are exemplary and for illustrative purposes only, and do not limit the subject matter of the invention in any way. In this invention, the singular is used in conjunction with the plural unless otherwise specifically stated. It should also be noted that, unless otherwise stated, the use of “or” or “or” means “and / or”. Furthermore, the use of the term “comprising” and other forms such as “including,” “containing,” and “contains” are not limiting.

[0013] See the references "Technology for Manufacturing Water-Soluble Supramolecular Complexes" and "Cosmetic Compositions Containing Supramolecular Compounds Capable of Forming Hydrogen Bonds and Specific Oils".

[0014] Unless otherwise stated, conventional methods within the scope of the art shall be used.

[0015] Unless specifically defined herein, the use of all commercially available products herein employs standard techniques. For example, it may be carried out using the manufacturer's instructions for use with the kit, or in accordance with methods known in the art or the description of this invention. The techniques and methods described herein can generally be implemented according to conventional methods well known in the art, based on the descriptions in the various summary and more specific documents cited and discussed in this specification.

[0016] As used herein, the term "supramolecular complex" refers to an ordered aggregate with a specific structure and function formed by the spontaneous assembly of two or more molecules through intermolecular non-covalent interactions (including but not limited to hydrogen bonds, van der Waals forces, π-π stacking, etc.). In this invention, the ectoine-malic acid supramolecular complex specifically refers to a binary supramolecular system formed by the intermolecular hydrogen bonding interactions between malic acid and ectoine.

[0017] As used herein, the term "hydrogen bond" refers to the electrostatic attraction between a hydrogen atom on an electronegative atom (such as oxygen or nitrogen) in one molecule and an electronegative atom (such as oxygen or nitrogen) in another molecule. In this invention, the carboxyl and hydroxyl groups in the malic acid molecule act as hydrogen bond donors, and the amide carbonyl and amino groups in the ectoine molecule act as hydrogen bond acceptors / donors, forming a multiple hydrogen bond network between them.

[0018] The term "redshift" as used herein refers to the phenomenon of an absorption peak in an infrared spectrum shifting towards lower wavenumbers. In this invention, the redshift of the malic acid carbonyl absorption peak (1718 cm⁻¹) is described. -1 →1711cm -1 1683cm -1 →1674cm -1 This indicates a change in the electron cloud density around the carbonyl group, confirming the formation of hydrogen bonds.

[0019] As used herein, the term "differential scanning calorimetry" or "DSC" refers to a technique that obtains the thermal transition temperature (such as melting, crystallization, glass transition, etc.) and enthalpy change of a sample by measuring the heat flow difference between the sample and a reference material during a programmed temperature rise process. In this invention, DSC is used to characterize the thermodynamic behavior of supramolecular complexes, and the appearance of a single endothermic peak indicates the formation of a new thermodynamically stable phase.

[0020] The term "endothermic peak" as used herein refers to the peak that appears in a DSC curve when the sample absorbs heat, corresponding to the melting or phase transition process of the sample. In this invention, the appearance of a single endothermic peak indicates that the composite has a uniform phase state and stable thermodynamic behavior.

[0021] In a first aspect, the present invention provides: an ectoine-malic acid supramolecular complex, wherein the ectoine-malic acid supramolecular complex is formed by the interaction of malic acid and ectoine through intermolecular hydrogen bonds; wherein the mass ratio of malic acid to ectoine is 2-3:1.

[0022] In this process, the two carboxyl groups and one hydroxyl group in the malic acid molecule act as hydrogen bond donors and acceptors, while the carboxyl group, secondary amino group, and imine group in the ectoine molecule act as hydrogen bond acceptors and donors. The two form a stable supramolecular complex structure through multiple hydrogen bond interaction sites.

[0023] Preferably, the mass ratio of malic acid to ectoine is 2:1.

[0024] Specifically, in the Fourier transform infrared spectrum of the ectoin-malic acid supramolecular complex: (1) 2500-3500cm -1 The region forms a broad absorption band; (2) The first carbonyl absorption peak of malic acid (1738 cm⁻¹) -1 Redshift occurs (left and right); (3) Absorption peak of the second carbonyl group of malic acid (1683 cm⁻¹) -1 Redshift occurs (left and right).

[0025] The ectoine-malic acid supramolecular complex exhibits a single endothermic peak at 160-180℃ in the differential scanning calorimetry curve.

[0026] First preferred option: An ectoine-malic acid supramolecular complex is formed by the interaction of malic acid and ectoine through intermolecular hydrogen bonds, wherein the mass ratio of malic acid to ectoine is 2-3:1.

[0027] This technical solution, based on the achievement of "supramolecular complex formation", further optimizes the technical issues of "complex fluidity and stability".

[0028] Secondly, this invention provides a method for preparing the above-mentioned ectoine-malic acid supramolecular complex.

[0029] The method for preparing the ectoine-malic acid supramolecular complex is characterized by comprising the following steps: (1) Add malic acid and ectoine to an organic solvent and stir to dissolve; (2) Remove the solvent under vacuum conditions; (3) A transparent and flowable supramolecular complex was obtained.

[0030] The organic solvent is anhydrous ethanol.

[0031] The stirring temperature is 70-90℃.

[0032] The pressure of the vacuum condition is -0.05 to -0.1 bar; preferably -0.1 bar.

[0033] Thirdly, this invention also provides the application of the ectoine-malic acid supramolecular complex in the preparation of skin care products.

[0034] The ectoine-malic acid supramolecular complex is used to reduce skin irritation, redness, and barrier damage caused by malic acid.

[0035] The skin care products are used to improve skin barrier function, relieve skin redness, reduce stinging sensation, improve skin tolerance, and soothe sensitive skin.

[0036] Examples 1-2 of this invention at least support the protection scope of the components and specific preparation method parameters of the ectoine-malic acid supramolecular complex.

[0037] The mass ratio of malic acid to ectoine and the stirring temperature mentioned herein are derived from the corresponding technical features "2:1, 3:1", "70℃, 90℃", etc., in the foregoing explanation and / or Examples 1-2, summarized by the common features "2-3:1" and "70-90℃". Therefore, those skilled in the art can reasonably infer that the technical features "mass ratio of malic acid to ectoine" and "stirring temperature", their subordinate concepts, their essentially equivalent technical means, and technical means that can replace them based on existing technology and conventional technical means and common knowledge, should all fall within its protection scope.

[0038] The beneficial effects of this invention are as follows: 1. Significantly Reduced Irritation: Through supramolecular complexation, the concentration of free malic acid is reduced, and human tests show a significant decrease in stinging scores. The free carboxyl groups of malic acid in the complex are supramolecularly encapsulated by forming hydrogen bonds with ectoine, reducing direct stimulation of nerve endings in the skin.

[0039] 2. Formation of a stable new phase: The formation of a new phase, rather than simple physical mixing, was confirmed by FTIR and DSC, resulting in stable product quality. The broadened absorption band and redshift of the carbonyl peak in the FTIR spectrum, as well as the appearance of a single new endothermic peak in the DSC curve, are strong evidence of the formation of a new phase.

[0040] 3. Simple preparation process: The present invention uses solvent evaporation method to prepare supramolecular complexes. The entire preparation process does not require complex equipment, the conditions are mild, the operation is simple, and it is suitable for large-scale industrial production. Attached Figure Description

[0041] Figure 1 This is the FTIR spectrum of malic acid.

[0042] Figure 2 FTIR spectrum of ectoine.

[0043] Figure 3 The FTIR spectrum of the ectoine-malic acid supramolecular complex prepared in Example 1 is shown.

[0044] Figure 4 DSC spectrum of malic acid Figure 5 DSC map of ectoine Figure 6 The image shows the DSC spectrum of the ectoine-malic acid supramolecular complex prepared in Example 1. Detailed Implementation

[0045] The following non-limiting embodiments are intended to enable those skilled in the art to gain a more comprehensive understanding of the present invention, but do not limit the invention in any way. The following content is merely an exemplary description of the scope of protection claimed by the present invention, and those skilled in the art can make various changes and modifications to the present invention based on the disclosed content, and such changes should also fall within the scope of protection claimed by the present invention.

[0046] The present invention will be further described below by way of specific embodiments. Unless otherwise specified, all instruments, devices, equipment, reagents, products, etc., used in the embodiments of the present invention are obtained through conventional commercial means.

[0047] Example 1 2g of malic acid and 1g of ectoine (mass ratio 2:1) were dispersed in 5g of anhydrous ethanol, dissolved under stirring at 90℃, and then distilled under reduced pressure at -0.1 bar for 30min.

[0048] Example 2 3g of malic acid and 1g of ectoine (mass ratio 3:1) were dispersed in 5g of anhydrous ethanol, dissolved under stirring at 70℃, and then distilled under reduced pressure at -0.1 bar for 40min.

[0049] Comparative Example 1 A gel sample was prepared according to Example 8 of patent CN115363978B.

[0050] Comparative Example 2 The difference from Example 1 is that the malic acid content is 1g and the ectoine content is 1g (mass ratio 1:1); the rest is the same as in Example 1.

[0051] Comparative Example 3 The difference from Example 1 is that the malic acid content is 1g and the ectoine content is 3g (mass ratio 1:3); the rest is the same as in Example 1.

[0052] Comparative Example 4 The difference from Example 1 is that: 5g of malic acid and 1g of ectoine (mass ratio 5:1) are dispersed in 10g of anhydrous ethanol; the rest is the same as in Example 1.

[0053] Verification of technical effectiveness and / or analysis of technical problem solving 1. Visual inspection The samples prepared in the above embodiments and comparative examples were subjected to visual inspection.

[0054] Table 1: Results of Visual Inspection

[0055] As shown in Table 1, the products obtained in Examples 1 and 2 are both transparent, flowable oily liquids without water, indicating that within this mass ratio range, malic acid and ectoine can completely associate through intermolecular hydrogen bonds to form a homogeneous supramolecular new phase without phase separation.

[0056] In Comparative Examples 2-4, white insoluble solids were observed. In Comparative Examples 2-3, ectoine was in relative excess, and the excess ectoine could not enter the supramolecular network and precipitated in crystal form; in Comparative Example 4, malic acid was in relative excess, and the excess malic acid also precipitated in solid form.

[0057] The above results indicate that the mass ratio of malic acid to ectoine is a key factor in whether a stable supramolecular complex can be formed. Only within a specific range, when the number of hydrogen bond donor and acceptor sites of the two components are matched, can a completely transparent, precipitated homogeneous complex be formed; outside this range, the homogeneous reaction is incomplete and a solid precipitates.

[0058] 2. FTIR spectral characterization Infrared spectroscopy analysis was performed on the samples from Example 1, malic acid, and ectoine.

[0059] Figure 1 This is the FTIR spectrum of malic acid. Figure 2 The FTIR spectrum of ectoine. Figure 3 The image shows the FTIR spectrum of the supramolecular complex in Example 1.

[0060] As attached Figure 1 As shown, malic acid at 3438 cm⁻¹ - A broad OH stretching vibration absorption peak appears near 1738 cm⁻¹. - ¹ and 1683cm - The characteristic absorption peak of the carboxylic acid carbonyl group C=O appears near ¹, at 1282 cm⁻¹. - ¹ and 1217cm - A CO stretching vibration peak appears near ¹. These characteristics indicate that the malic acid molecule contains abundant hydroxyl and carboxyl groups, and has a strong hydrogen bond donor capacity.

[0061] As attached Figure 2 As shown, ectoine is at 3178cm - An absorption peak for the NH stretching vibration appears near 1652 cm⁻¹. - A characteristic absorption peak for the carbonyl group of carboxylic acids appears near ¹, at 1586 cm⁻¹. - An absorption peak coupling NH bending vibration and CN stretching vibration was observed near ¹. This result indicates that ectoine contains a carboxyl group and a nitrogen-containing heterocycle, and possesses both hydrogen bond donor and acceptor sites.

[0062] As attached Figure 3 As shown, compared with malic acid and ectoine monomers, the ectoine-malic acid supramolecular complex exhibits higher molecular weight distribution in the 2500–3500 cm⁻¹ range. - The significantly broadened absorption band in region ¹ indicates the formation of a stronger intermolecular hydrogen bond network in the system. Simultaneously, the absorption peak of the first carbonyl group of malic acid increased from 1738 cm⁻¹. - ¹Moved to 1714cm - ¹, The absorption peak of the second carbonyl group of malic acid is from 1683 cm⁻¹ - ¹Move to 1655cm - ¹, the intensity and shape of the carbonyl absorption peak of ectocarboxylic acid also changed.

[0063] The above phenomena indicate a significant intermolecular interaction between the carboxyl and hydroxyl groups of malic acid and the carbonyl group of ectoinamide. Furthermore, at 1500–1200 cm⁻¹... - ¹The peak shape in the fingerprint region also changed significantly, indicating that the obtained product was not a simple physical mixture of the two raw materials, but rather formed a new molecular association structure.

[0064] Therefore, it can be inferred that malic acid and ectoine form a stable binary supramolecular complex system through multiple hydrogen bonding interactions.

[0065] 3. DSC characterization DSC analysis was performed on the samples from Example 1, malic acid, and ectoine.

[0066] Figure 4 This is the DSC spectrum of malic acid. Figure 5 The DSC spectrum of ectoine. Figure 6 The image shows the DSC spectrum of the supramolecular complex described in Example 1.

[0067] As attached Figure 4 and attached Figure 5 As shown, malic acid exhibits a characteristic endothermic peak at approximately 133°C, while ectoine exhibits a characteristic endothermic peak at approximately 140°C. Both demonstrate their own independent thermal behavior characteristics. In Example 1, the original characteristic peaks at 133°C (malic acid) and 140°C (ectoine) in the ectoine-malic acid supramolecular complex disappeared, and a new single endothermic peak at 177°C appeared.

[0068] The results indicate that malic acid and ectoine form a new thermodynamic phase after supramolecular assembly, with thermal behavior distinct from that of the individual monomeric raw materials. If it were merely a simple physical mixture, the DSC curve should retain the original characteristic endothermic peaks of each component. However, the experimental results show that the original characteristic peaks completely disappeared, replaced by a new, single endothermic peak. This indicates that the complex is not a simple addition of the two components, but rather a new form of matter with independent thermodynamic behavior. Combined with the FTIR results, it is evident that stable intermolecular interactions formed between malic acid and ectoine, thus constructing a new binary supramolecular system.

[0069] 4. Application Examples and Comparative Examples To verify the efficacy and safety of the supramolecular complex of the present invention in actual skin care products, an essence containing the supramolecular complex (application example) and a control essence containing different active ingredients (application comparison examples 1-4) were prepared and subjected to multiple performance tests.

[0070] The basic matrix formula is as follows: hyaluronic acid: 0.15%, xanthan gum: 0.2%, glycerin: 5.0%, propylene glycol: 3.0%, p-hydroxyacetophenone: 0.5%, 1,2-hexanediol: 1.0%, EDTA 2Na: 0.1%, and deionized water to bring the total to 100%.

[0071] Application Examples (containing 3% supramolecular complex) Add 3% of the malic acid-ectoine supramolecular complex prepared in Example 1 (malic acid:ectoine = 2:1, equivalent to containing 2% malic acid and 1% ectoine) to the above basic matrix and stir until homogeneous.

[0072] Blank comparison example (blank matrix) Using only the above-mentioned basic matrix, without adding any active ingredients.

[0073] Comparative Example 1 (physical mixture containing 2% malic acid + 1% ectoine) 2% pure malic acid and 1% pure ectoine were added to the above basic matrix and directly stirred to dissolve (without solvent evaporation treatment). This comparative ratio is exactly the same as the total content of malic acid and ectoine in the application examples, the only difference being whether a supramolecular complex is formed.

[0074] Comparative Example 2 (containing 2% malic acid) was applied. Add 2% malic acid to the above base matrix and stir to dissolve.

[0075] Comparative Example 3 (containing 1% ectoine) Add 1% ectoine to the above base matrix and stir to dissolve.

[0076] Application Comparative Example 4 That is, the gel sample prepared in Comparative Example 1.

[0077] 5. Human skin sting test Subjects: Twenty subjects with sensitive skin, aged 20-45 years, were selected, with an equal number of men and women. Pregnant or breastfeeding women, those with skin diseases, or those currently using medications that affect skin condition were excluded.

[0078] Test Method: A single-center, single-blind, self-controlled design with left and right face measurements was used. Before the test, subjects cleaned their faces with warm water and acclimatized for 30 minutes in a constant temperature and humidity chamber (temperature 22±1℃, relative humidity 50±5%). 0.05 mL of each sample was applied to the skin on both sides of the nasolabial folds, and the stinging sensation was scored on a scale of 0-5 at 1 min, 5 min, and 15 min after application.

[0079] Scoring criteria: 0 points = no stinging, 1 point = mild stinging, 2 points = moderate stinging, 3 points = obvious stinging, 4 points = severe stinging, 5 points = unbearable.

[0080] Human skin stinging test results

[0081] The results above show that the scores of the blank matrix at each time point are close to those of the application control group 3, indicating that ectoine itself is well tolerated and causes almost no stinging.

[0082] The scores at each time point in the application example were significantly lower than those in Comparative Examples 1, 2, and 4. Comparative Example 1's scores at each time point were 1.47±0.18, 2.42±0.21, and 2.58±0.19, respectively. Although there was a decrease, the score at 15 minutes remained in the "moderate tingling" range, indicating that simply adding ectoine through physical mixing could not block the direct effect of free carboxyl groups on nerve endings. Comparative Example 4 (i.e., closest to the prior art) had a score of 2.81±0.26 at 15 minutes, also remaining at a moderately high level. This suggests that simple physical mixing of the two components cannot form a supramolecular structure and therefore cannot block the stimulation of free acid.

[0083] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention do not depart from the essence and scope of the technical solution of the present invention.

Claims

1. An ectoine-malic acid supramolecular complex, characterized in that, The ectoine-malic acid supramolecular complex is formed by the interaction of malic acid and ectoine through intermolecular hydrogen bonds; the mass ratio of malic acid to ectoine is 2-3:

1.

2. The ectoine-malic acid supramolecular complex according to claim 1, characterized in that, The mass ratio of malic acid to ectoine is 2:

1.

3. The ectoine-malic acid supramolecular complex according to any one of claims 1-2, characterized in that, The Fourier transform infrared spectrum of the ectoin-malic acid supramolecular complex has the following characteristics: (1) A broad absorption band forms in the 2500-3500cm-1 region; (2) The first carbonyl absorption peak of malic acid (around 1738 cm-1) undergoes a red shift; (3) The absorption peak of the second carbonyl group of malic acid (around 1683 cm-1) undergoes a red shift.

4. The ectoine-malic acid supramolecular complex according to any one of claims 1-2, characterized in that, The ectoine-malic acid supramolecular complex exhibits a single endothermic peak at 160-180℃ in the differential scanning calorimetry curve.

5. A method for preparing the ectoine-malic acid supramolecular complex according to any one of claims 1-2, characterized in that, Includes the following steps: (1) Add malic acid and ectoine to an organic solvent and stir to dissolve; (2) Remove the solvent under vacuum conditions; (3) A transparent and flowable supramolecular complex was obtained.

6. The preparation method according to claim 5, characterized in that, The organic solvent is anhydrous ethanol.

7. The preparation method according to claim 5, characterized in that, The stirring temperature is 70-90℃.

8. The use of the ectoine-malic acid supramolecular complex according to any one of claims 1-2 in the preparation of skin care products.

9. The application according to claim 8, characterized in that, The skin care product is designed to reduce skin irritation, redness, and barrier damage caused by malic acid.

10. The application according to claim 8 or 9, characterized in that, The skin care products mentioned are those that can improve skin barrier function, relieve skin redness, reduce stinging sensation, improve skin tolerance, and soothe sensitive skin.

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