A pH-responsive vaccinium uliginosum leaf polyphenol antioxidant matrix, and a preparation method and application thereof

Abstract

This invention discloses a pH-responsive red bean and blueberry leaf polyphenol antioxidant matrix, its preparation method, and its application, belonging to the field of cosmetics / topical skincare technology. It addresses the technical problems of existing red bean and blueberry liquid extracts having fixed physicochemical properties, unable to adapt to skin pH, and with active ingredients easily leaching from the skin surface after application. This invention uses red bean and blueberry leaves as raw material to extract polyphenols, uses SP207 macroporous resin for gradient elution and screening of highly active polyphenol fractions, concentrates after alcohol removal, and adds calcium chloride solution to prepare a pH-responsive antioxidant matrix. Under the slightly acidic pH conditions simulating healthy skin, this matrix exhibits a lighter color and better fluidity compared to an inflammatory environment; under the neutral pH conditions corresponding to inflamed skin, the system's color deepens, and its liquid retention capacity is enhanced, delaying liquid slippage and prolonging the duration of action of polyphenolic active substances on the surface, achieving differentiated antioxidant sustained-release effects for different skin conditions.

Description

Technical Field

[0001] This invention belongs to the field of cosmetics / topical skin care products technology, and particularly relates to a pH-responsive red bean and blueberry leaf polyphenol antioxidant matrix, its preparation method and application. Background Technology

[0002] Red bilberry (Vaccinium vitis-idaea Linn.) is a plant belonging to the genus Vaccinium in the family Ericaceae. Its leaves are rich in polyphenolic active ingredients such as chlorogenic acid, caffeic acid, flavonoid glycosides, and proanthocyanidins, exhibiting significant in vitro antioxidant activity. Literature reports indicate that the content of ursolic acid and polyphenols in red bilberry leaves is higher than that in its fruit. Furthermore, as a byproduct of processing, the leaves are widely available and inexpensive, possessing high development and utilization potential in the fields of functional food ingredients and skin care. However, the resource utilization of red bilberry leaves is currently insufficient. Existing technologies mainly focus on the qualitative and quantitative analysis of the components of crude leaf extracts and preliminary exploration of oral formulations, without the formation of a systematic and sophisticated processing technology system.

[0003] Currently, most finished products of red bean and blueberry extract are lyophilized powders or conventional aqueous solutions, with a few formulated as gels, creams, and other topical dosage forms. Lyophilized powders require reconstitution before use, adding to the processing steps; gels and creams require the addition of carbomer, gellan gum, liposomes, and other high-molecular-weight gelling or emulsifying excipients, resulting in complex formulations and increased external ingredients. Conventional liquid extracts have low flow resistance and excessive fluidity after spreading, making them easily lost due to gravity when applied to the skin. This results in a short residence time for active substances on the skin surface, insufficient long-lasting and sustained-release repair effects. More importantly, current research on red bean and blueberry extract formulations only utilizes its inherent antioxidant activity; the color and fluid spreading characteristics of the finished product are fixed values, failing to adapt to the different pH environments of healthy and inflamed skin, lacking differentiated response performance under different skin conditions. Summary of the Invention

[0004] To address the lack of pH-responsive adaptive adjustment capabilities in existing red bean and blueberry leaf extract formulations, this invention provides a pH-responsive red bean and blueberry leaf polyphenol antioxidant matrix, its preparation method, and its application.

[0005] The technical solution of the present invention:

[0006] A method for preparing a pH-responsive red bean and blueberry leaf polyphenol antioxidant matrix includes the following steps:

[0007] Step 1: Crush the dried leaves of red bean and blueberry, extract with ethanol aqueous solution, separate solid and liquid, collect the filtrate, remove alcohol, concentrate, and obtain crude extract concentrate of red bean and blueberry leaf polyphenols;

[0008] Step 2: Pass the crude extract concentrate obtained in Step 1 into an SP207 macroporous adsorption resin column for adsorption. Perform gradient elution with ethanol aqueous solutions of 30%, 40%, 50%, 60%, 70%, and 80% (v / v), and collect the fractions of each concentration. Detect the ABTS (2,2'-azo-bis(3-ethylbenzothiazole-6-sulfonic acid) diammonium salt) free radical scavenging rate of each fraction. Use a scavenging rate >50% as the screening criterion and collect at least one of the 50% ethanol fraction, 60% ethanol fraction, and 70% ethanol fraction.

[0009] Step 3: De-alcoholize and concentrate the fraction collected in Step 2 to obtain a polyphenol concentrate;

[0010] Step 4: Add calcium chloride aqueous solution to the polyphenol concentrate obtained in Step 3, stir and mix well to obtain pH-responsive red bean and blueberry leaf polyphenol antioxidant matrix.

[0011] Furthermore, in step one, the volume fraction of the ethanol-water solution is 60-80%, the extraction material-to-liquid ratio is 1 g: 50 mL, the extraction temperature is 40℃, and the extraction time is 2 hours; the concentration is to concentrate to 1 / 10 of the volume after de-alcoholization.

[0012] Furthermore, in step two, the volume of eluent of each concentration in the gradient elution is 3 times the column volume, and the elution flow rate is 1.0 mL / min.

[0013] Furthermore, in step three, the concentration is carried out to 1 / 7 of the volume after alcohol removal.

[0014] Furthermore, in step four, the calcium chloride aqueous solution has a mass fraction of 10%, and the amount added is 40 μL of calcium chloride aqueous solution per 10 mL of polyphenol concentrate.

[0015] A pH-responsive red bean and blueberry leaf polyphenol antioxidant matrix is ​​prepared by the method provided in this invention.

[0016] Furthermore, the matrix exhibits different colors and flow resistance at pH 4.7 and pH 7.0, with the color being deeper and the flow resistance greater at pH 7.0 than at pH 4.7.

[0017] The application of a pH-responsive red bean and blueberry leaf polyphenol antioxidant matrix prepared according to the present invention in the preparation of topical skin care formulations.

[0018] Furthermore, the topical skin care preparation is a liquid matrix for direct application to the skin surface. After the matrix is ​​applied to the skin, it spontaneously changes color according to the skin's pH and achieves differentiated sustained release and retention.

[0019] Furthermore, the topical skin care preparation is a serum, lotion, or spray.

[0020] The beneficial effects of this invention are:

[0021] This invention combines a concentrated extract of red bean and blueberry leaf polyphenols obtained through gradient elution with SP207 resin and ABTS activity screening with calcium chloride to construct a pH-responsive red bean and blueberry leaf polyphenol antioxidant matrix. This matrix exhibits differentiated color characteristics and rheological properties in healthy skin at pH 4.7 and inflamed / damaged skin at pH 7.0. In the inflamed / damaged skin environment at pH 7.0, the matrix color deepens, flow resistance increases, and the rate of sliding off the skin surface decreases, effectively prolonging the retention time of active polyphenol components on the skin surface, achieving differentiated sustained release and retention of antioxidant active ingredients on the skin. While exerting its antioxidant and repairing effects on the skin, this matrix can also provide a visual indication of the skin's pH state through color changes, overcoming the technical shortcomings of traditional skincare products that have single, fixed physicochemical properties and lack the ability to adaptively regulate the skin environment.

[0022] This invention uses red bean and blueberry leaves as the extraction raw material, broadening the application channels of red bean and blueberry by-products and improving the comprehensive utilization rate of plants. Addressing the technical challenges of difficult extraction of polyphenols and low enrichment of active ingredients from leaves, this invention employs SP207 macroporous adsorption resin for a 30%–80% ethanol gradient elution process. ABTS free radical scavenging rate is used as the activity evaluation screening index to selectively enrich the highly active polyphenol fraction in the 50%–70% ethanol elution stage. This preparation process eliminates the need for complex subsequent purification steps such as ultrafiltration, nanofiltration, and freeze-drying, requiring less equipment investment and a shorter process flow, thus reducing the cost of industrial-scale production.

[0023] The product obtained by this invention is a liquid system, which does not require the addition of carbomer, liposomes, or polymeric gel-like gelling agents. The formulation is simple and can be used directly as a topical skin care solution or as a functional active ingredient to be compounded and processed into various daily chemical products such as serums, lotions, and sprays. The formulation has excellent adaptability and application compatibility. Attached Figure Description

[0024] Figure 1 A comparison of ABTS free radical scavenging rates of red bean and blueberry leaf polyphenols in different ethanol-eluted fractions;

[0025] Figure 2 A comparison of ABTS free radical scavenging rates of polyphenol concentrates with 50%, 60%, and 70% components, and polyphenol matrices at pH 4.7 and pH 7.0.

[0026] Figure 3A comparison of DPPH free radical scavenging rates of polyphenol concentrates with 50%, 60%, and 70% components, and polyphenol matrices at pH 4.7 and pH 7.0;

[0027] Figure 4 Comparison of the apparent color and transmittance of 60% polyphenol concentrate stock solution, polyphenol matrix at pH 4.7 and pH 7.0 and pure water. A represents the apparent color and B represents the transmittance.

[0028] Figure 5 Photos taken during the testing process of fluid adhesion properties of polyphenol matrices with different components;

[0029] Figure 6 A comparison of residence time in the fluid adhesion performance test of polyphenol matrix for pure water, 50%, 60%, and 70% polyphenol concentrate, pH 4.7, and pH 7.0. Detailed Implementation

[0030] The technical solution of the present invention will be further described below with reference to embodiments, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention. In the following embodiments, the process equipment or apparatus not specifically specified are all conventional equipment or apparatus in the art. Unless otherwise specified, the raw materials used in the embodiments of the present invention are all commercially available; unless otherwise specified, the technical means used in the embodiments of the present invention are all conventional means well known to those skilled in the art.

[0031] Example 1

[0032] This embodiment provides a method for preparing a pH-responsive red bean and blueberry leaf polyphenol antioxidant matrix, the specific steps of which are as follows:

[0033] Step 1: Preparation of crude extract of red bean and blueberry leaf polyphenols:

[0034] The dried leaves of red bean and blueberry were pulverized and passed through a 40-mesh sieve. 100 g of the powder was added to a 70% (v / v) ethanol aqueous solution at a material-to-liquid ratio of 1 g: 50 mL. The mixture was heated and stirred in a 40°C water bath for 2 hours to extract the powder. The solid residue was removed by filtration, and the filtrate was collected. The ethanol was removed by rotary evaporation under reduced pressure at 45°C to obtain an aqueous extract. This aqueous extract was further concentrated under reduced pressure to 1 / 10 of its original volume after alcohol removal, yielding a crude extract of red bean and blueberry leaf polyphenols, which was stored at 4°C for later use.

[0035] Step 2: Gradient elution purification with SP207 macroporous resin:

[0036] The SP207 macroporous adsorption resin was soaked in 95% ethanol for 24 hours to fully swell, washed with distilled water until the effluent had no alcohol odor, and then soaked in 5% hydrochloric acid solution and 5% sodium hydroxide solution for 4 hours each. After each acid and alkali soaking, the resin was washed with distilled water until the effluent was neutral. The resin was then wet-packed into the chromatography column and sealed for later use.

[0037] The crude extract of red bean and blueberry leaf polyphenols prepared in step one was fed into an SP207 macroporous adsorption resin column at a flow rate of 1.0 mL / min to complete static adsorption. After loading, the resin column was rinsed with distilled water to remove unadsorbed water-soluble impurities.

[0038] Fractional gradient elution was performed sequentially using ethanol-water solutions with volume fractions of 30%, 40%, 50%, 60%, 70%, and 80%, with each concentration of eluent used at a volume of 3 times the column volume and an elution flow rate of 1.0 mL / min. Each concentration fraction was collected separately.

[0039] The ABTS free radical scavenging rate of each fraction was tested, and the ABTS scavenging rate of the original eluent after alcohol removal was >50% was used as the activity screening criterion.

[0040] The results are as follows Figure 1 As shown, the ABTS scavenging rate of the 30%, 40%, and 80% ethanol eluent fractions is less than 50%, indicating relatively poor free radical scavenging ability. Therefore, the 30%, 40%, and 80% ethanol eluent fractions are discarded; the three highly active fractions of 50%, 60%, and 70% are retained as raw materials for the subsequent molding system.

[0041] Step 3: De-alcoholization and concentration of the purified solution:

[0042] The 50% ethanol eluent collected in step two was subjected to rotary evaporation under reduced pressure at 45°C to completely remove the ethanol. The aqueous solution after ethanol removal was further concentrated under reduced pressure to 1 / 7 of the volume after ethanol removal, yielding a concentrated polyphenol solution of 50% ethanol eluent, which was stored at 4-10°C in the dark for later use.

[0043] Step 4: Preparation of pH-responsive antioxidant matrix:

[0044] Take the polyphenol concentrate eluted with 50% ethanol, add calcium chloride at a ratio of 40 μL of 10% calcium chloride aqueous solution per 10 mL of polyphenol concentrate, stir and mix well to obtain the pH-responsive red bean and blueberry leaf polyphenol antioxidant matrix.

[0045] Example 2

[0046] This embodiment provides a method for preparing a pH-responsive red bean and blueberry leaf polyphenol antioxidant matrix. The only difference between this embodiment and Example 1 is that:

[0047] Step 3: De-alcoholization and concentration of the purified solution:

[0048] The 60% ethanol eluent collected in step two was subjected to rotary evaporation under reduced pressure at 45°C to completely remove the ethanol. The aqueous solution after ethanol removal was further concentrated under reduced pressure to 1 / 7 of the volume after ethanol removal, yielding a concentrated polyphenol solution of 60% ethanol eluent, which was stored at 4-10°C in the dark for later use.

[0049] Step 4: Preparation of pH-responsive antioxidant matrix:

[0050] Take the polyphenol concentrate eluted with 60% ethanol, add calcium chloride at a ratio of 40 μL of 10% calcium chloride aqueous solution per 10 mL of polyphenol concentrate, stir and mix well to obtain the pH-responsive red bean and blueberry leaf polyphenol antioxidant matrix.

[0051] Example 3

[0052] This embodiment provides a method for preparing a pH-responsive red bean and blueberry leaf polyphenol antioxidant matrix. The only difference between this embodiment and Example 1 is that:

[0053] Step 3: De-alcoholization and concentration of the purified solution:

[0054] The 70% ethanol eluent collected in step two was subjected to rotary evaporation under reduced pressure at 45°C to completely remove the ethanol. The aqueous solution after ethanol removal was further concentrated under reduced pressure to 1 / 7 of the volume after ethanol removal, yielding a concentrated polyphenol solution of 70% ethanol eluent, which was stored at 4-10°C in the dark for later use.

[0055] Step 4: Preparation of pH-responsive antioxidant matrix:

[0056] Take the polyphenol concentrate eluted with 70% ethanol, add calcium chloride at a ratio of 40 μL of 10% calcium chloride aqueous solution per 10 mL of polyphenol concentrate, stir and mix well to obtain the pH-responsive red bean and blueberry leaf polyphenol antioxidant matrix.

[0057] Experimental Example 1

[0058] To simulate the environment of healthy skin (pH 4.5~5.0), the pH of the system was adjusted to 4.7 when preparing the antioxidant matrix in this experiment. The only difference between this experiment and Example 1 is that:

[0059] Step 4: Preparation of pH-responsive antioxidant matrix:

[0060] Take the polyphenol concentrate eluted with 50% ethanol, adjust the pH of the system to 4.7 with baking soda, and then add calcium chloride at a ratio of 40 μL of 10% calcium chloride aqueous solution per 10 mL of polyphenol concentrate. Stir and mix well. The resulting polyphenol antioxidant matrix is ​​used for performance testing.

[0061] Experimental Example 2

[0062] To simulate the environment of inflamed / damaged skin (pH 7.0~8.0), the pH of the system was adjusted to 7.0 when preparing the antioxidant matrix in this experiment. The only difference between this method and Example 1 is that:

[0063] Step 4: Preparation of pH-responsive antioxidant matrix:

[0064] Take the polyphenol concentrate eluted with 50% ethanol, adjust the pH of the system to 7.0 with baking soda, and then add calcium chloride at a ratio of 40 μL of 10% calcium chloride aqueous solution per 10 mL of polyphenol concentrate. Stir and mix well. The resulting polyphenol antioxidant matrix is ​​used for performance testing.

[0065] Experimental Example 3

[0066] To simulate a healthy skin environment (pH 4.5~5.0), the pH of the system was adjusted to 4.7 during the preparation of the antioxidant matrix in this experiment. The only difference between this method and Example 2 is that:

[0067] Step 4: Preparation of pH-responsive antioxidant matrix:

[0068] Take the polyphenol concentrate eluted with 60% ethanol, adjust the pH of the system to 4.7 with baking soda, then add calcium chloride at a ratio of 40 μL of 10% calcium chloride aqueous solution per 10 mL of polyphenol concentrate, stir and mix well, and use the obtained polyphenol antioxidant matrix for performance testing.

[0069] Test Example 4

[0070] To simulate an inflamed / damaged skin environment (pH 7.0~8.0), the pH of the system was adjusted to 7.0 during the preparation of the antioxidant matrix in this experiment. The only difference between this method and Example 2 is that:

[0071] Step 4: Preparation of pH-responsive antioxidant matrix:

[0072] Take the polyphenol concentrate eluted with 60% ethanol, adjust the pH of the system to 7.0 with baking soda, and then add calcium chloride at a ratio of 40 μL of 10% calcium chloride aqueous solution per 10 mL of polyphenol concentrate. Stir and mix well. The resulting polyphenol antioxidant matrix is ​​used for performance testing.

[0073] Experimental Example 5

[0074] To simulate the environment of healthy skin (pH 4.5~5.0), the pH of the system was adjusted to 4.7 when preparing the antioxidant matrix in this experiment. The only difference between this method and Example 3 is that:

[0075] Step 4: Preparation of pH-responsive antioxidant matrix:

[0076] Take the polyphenol concentrate eluted with 70% ethanol, adjust the pH of the system to 4.7 with baking soda, and then add calcium chloride at a ratio of 40 μL of 10% calcium chloride aqueous solution per 10 mL of polyphenol concentrate. Stir and mix well. The resulting polyphenol antioxidant matrix is ​​used for performance testing.

[0077] Experimental Example 6

[0078] To simulate an inflamed / damaged skin environment (pH 7.0~8.0), the pH of the system was adjusted to 7.0 during the preparation of the antioxidant matrix in this experiment. The only difference between this method and Example 3 is that:

[0079] Step 4: Preparation of pH-responsive antioxidant matrix:

[0080] Take the polyphenol concentrate eluted with 70% ethanol, adjust the pH of the system to 7.0 with baking soda, then add calcium chloride at a ratio of 40 μL of 10% calcium chloride aqueous solution per 10 mL of polyphenol concentrate, stir and mix well, and use the obtained polyphenol antioxidant matrix for performance testing.

[0081] The antioxidant activity, color transmittance, and fluid adhesion properties of the polyphenol concentrates eluted with 50%, 60%, and 70% ethanol prepared in Examples 1-3, as well as the various pH-adjustable antioxidant matrices prepared in Examples 1-6, were tested. The specific methods and test results are as follows:

[0082] I. Antioxidant Activity Detection

[0083] 1. ABTS free radical scavenging rate detection

[0084] Detection method: Mix 7 mmol / L ABTS aqueous solution with 2.45 mmol / L potassium persulfate aqueous solution in equal volumes, and let stand at room temperature in the dark for 12-16 hours. Dilute with phosphate buffer to a absorbance of 0.70±0.02 at 734 nm to prepare ABTS working solution.

[0085] The 50%, 60%, and 70% ethanol eluent polyphenol concentrates prepared in Examples 1-3, and the pH-adjusting antioxidant matrices prepared in Examples 1-6 were diluted 10 times to obtain the samples to be tested.

[0086] Each sample was mixed with ABTS working solution at a 1:1 volume ratio and reacted at room temperature for 6 minutes. The absorbance was measured at a wavelength of 734 nm, and the ABTS scavenging rate was calculated.

[0087] The results are as follows Figure 2As shown, the ABTS scavenging rates of the polyphenol fractions eluted with 50%, 60%, and 70% ethanol under the three pH conditions all followed the trend of concentrated stock solution group > pH 4.7 group > pH 7.0 group. The 60% fraction exhibited the best antioxidant stability, retaining high free radical scavenging capacity at both pH 4.7 and pH 7.0; the 70% fraction showed the second best stability; the antioxidant activity of the 50% fraction was most significantly affected by pH, with the most obvious activity decay at pH 7.0. Since the samples were diluted 10-fold during testing, the actual scavenging rates of the three polyphenol fractions were close to 100% after conversion, all demonstrating excellent antioxidant activity.

[0088] 2. DPPH free radical scavenging rate detection

[0089] Detection method: Mix 2 mL of 0.1 mmol / L DPPH ethanol solution with 2 mL of the sample to be tested, react at room temperature in the dark for 30 minutes, and measure the absorbance at a wavelength of 517 nm to calculate the DPPH scavenging rate. All samples were also diluted 10 times before detection.

[0090] The results are as follows Figure 3 As shown, the DPPH scavenging rates of the polyphenol components eluted with 50%, 60%, and 70% ethanol in the three test systems all followed the pattern of concentrated stock solution group > pH 4.7 group > pH 7.0 group. Among them, the 60% component had the best DPPH free radical scavenging ability and pH stability, followed by the 70% component, while the 50% component showed a relatively significant activity decline under pH 7.0 conditions. Since the samples were diluted 10 times during the test, the actual scavenging rates of the polyphenols in all three groups were close to 100% after conversion, all of which showed excellent antioxidant activity.

[0091] The above results indicate that the polyphenol composition of the eluted fractions differs depending on the ethanol concentration: the 50% fraction is dominated by small-molecule phenolic acids, exhibiting good stability at high concentrations and performing best in the aqueous ABTS system; the 60% fraction is dominated by polyproanthocyanidins, with the highest total polyphenol content, and performs best in the alcoholic DPPH system due to its balanced solubility and numerous monohydroxyl groups; the 70% fraction is composed of low-polarity flavonoid aglycones with a relatively low total polyphenol content. Although the activity ranking of the three fractions differs in different detection systems, all three exhibit excellent antioxidant activity and can be considered effective components of pH-responsive antioxidant matrices.

[0092] II. Color and transmittance testing

[0093] Take the 60% concentrated stock solution prepared in Example 2, the sample from Test Example 3 (pH 4.7 group), and the sample from Test Example 4 (pH 7.0 group), place them in cuvettes, and observe the color differences, using distilled water as a control. Place a piece of paper with the word "Test" written on it behind the cuvettes and observe the clarity of the writing through the solution; at the same time, use a UV-Vis spectrophotometer to measure the absorbance value of each group of samples in the visible light region. The results are shown in Table 1.

[0094] The results are as follows Figure 4 As shown, the results of visual observation are as follows: the concentrated stock solution and the pH 4.7 solution are relatively clear and transparent, while the pH 7.0 solution is significantly darker in color. The results of transmittance observation are as follows: the writing is clearly visible in the distilled water; it is faintly visible in the concentrated stock solution and the pH 4.7 solution; the writing is the most blurred in the pH 7.0 solution, indicating that it has the lowest transmittance.

[0095] Table 1

[0096]

[0097] As shown in Table 1, the absorbance test results are consistent with visual observation: the absorbance values ​​of all components in the pH 7.0 sample are significantly higher than those in the corresponding pH 4.7 sample and the concentrated stock solution, indicating that the color deepens and the transmittance decreases under pH 7.0 conditions. The absorbance values ​​of the 70% component in all states are higher than those of the corresponding 50% and 60% samples, which is related to the darker color of the 70% component itself, but the pattern of "pH 7.0 > pH 4.7" within the same group remains consistent.

[0098] III. Fluid Adhesion Performance Test (Inclined Plane Drop Test)

[0099] To simulate the flow behavior of liquid care matrix under different human facial postures, two test scenarios were set up: a gentle slope (40°) and a vertical situation (90°).

[0100] 1. Quantitative testing on a 40° gentle slope

[0101] like Figure 5 As shown, the slotted computer stand was fixed at a 40° tilt angle. A disposable six-well plate cover was used as a smooth inclined surface base and placed horizontally on the stand. 50 μL each of distilled water, the concentrated stock solutions prepared in Examples 1-3, and the pH-adjusting samples prepared in Examples 1-6 were added to the same height on the inclined surface (with a set drop path of 8 cm). Timing was started, and the time taken for the fluid to slide from the front end to the bottom endpoint was recorded. The upper limit of observation was set to 300 seconds; any sample that did not slide to the endpoint within 300 seconds was recorded as ">300s". Each sample was tested three times, and the average value was taken.

[0102] The results are as follows Figure 6As shown, distilled water slid down the fastest, reaching the endpoint within seconds; the concentrated stock solutions and the pH 4.7 group slid down significantly slower than distilled water; the pH 7.0 group slid down the slowest. Notably, the 50% and 60% components (pH 7.0) did not reach the bottom within the 300-second observation limit, exhibiting the longest residence time and demonstrating superior fluid adhesion properties compared to conventional liquid extracts.

[0103] 2. Qualitative observation of 90° vertical situations

[0104] A brand-new disposable six-well plate cover was vertically attached to the wall. 50 μL of each of the above samples was collected and applied to the same height at the top of the cover, and the entire process was recorded on video. At this angle, gravity is extremely strong, and all fluids slide down at relatively high speeds. However, the order in which they slide down is still clearly discernible to the naked eye: distilled water slides down first, followed by the concentrated stock solution and the pH 4.7 group, with the pH 7.0 group consistently being the last sample to slide down, consistent with the trend observed in the quantitative results from the 40° inclined plane.

[0105] The plastic cover used in the experiment was a low-friction smooth surface. However, the human face has structures such as pores, skin texture, and hair, and the surface adhesion resistance is higher than that of smooth plastic. It can be reasonably inferred that the antioxidant matrix prepared by this invention will have a more significant anti-flow and long-lasting adhesion effect when actually used on the face.

Claims

1. A method for preparing a pH-responsive red bean and blueberry leaf polyphenol antioxidant matrix, characterized in that, Includes the following steps: Step 1: Crush the dried leaves of red bean and blueberry, extract with ethanol aqueous solution, separate solid and liquid, collect the filtrate, remove alcohol, concentrate, and obtain crude extract concentrate of red bean and blueberry leaf polyphenols; Step 2: Pass the crude extract concentrate obtained in Step 1 into an SP207 macroporous adsorption resin column for adsorption. Perform gradient elution with ethanol aqueous solutions of 30%, 40%, 50%, 60%, 70%, and 80% (v / v), and collect the fractions of each concentration. Detect the ABTS free radical scavenging rate of each fraction. Use a scavenging rate >50% as the screening criterion and collect at least one of the 50% ethanol fraction, 60% ethanol fraction, and 70% ethanol fraction. Step 3: De-alcoholize and concentrate the fraction collected in Step 2 to obtain a polyphenol concentrate; Step 4: Add calcium chloride aqueous solution to the polyphenol concentrate obtained in Step 3, stir and mix well to obtain pH-responsive red bean and blueberry leaf polyphenol antioxidant matrix.

2. The preparation method according to claim 1, characterized in that, In step one, the volume fraction of the ethanol-water solution is 60-80%, the material-to-liquid ratio is 1 g:50 mL, the extraction temperature is 40℃, and the extraction time is 2 hours; the concentration is to concentrate to 1 / 10 of the volume after de-alcoholization.

3. The preparation method according to claim 1 or 2, characterized in that, In step two, the volume of eluent of each concentration in the gradient elution is 3 times the column volume, and the elution flow rate is 1.0 mL / min.

4. The preparation method according to claim 3, characterized in that, In step three, the concentration is to concentrate to 1 / 7 of the volume after alcohol removal.

5. The preparation method according to claim 4, characterized in that, In step four, the calcium chloride aqueous solution has a mass fraction of 10%, and the amount added is 40 μL of calcium chloride aqueous solution per 10 mL of polyphenol concentrate.

6. A pH-responsive red bean and blueberry leaf polyphenol antioxidant matrix, characterized in that, It is prepared by the preparation method according to any one of claims 1-5.

7. The pH-responsive red bean and blueberry leaf polyphenol antioxidant matrix according to claim 6, characterized in that, The matrix exhibits different colors and flow resistance at pH 4.7 and pH 7.0, with the color being darker and the flow resistance greater at pH 7.0 than at pH 4.

7.

8. The use of a pH-responsive red bean and blueberry leaf polyphenol antioxidant matrix as described in claim 6 or 7 in the preparation of topical skin care formulations.

9. The application according to claim 8, characterized in that, The skin care preparation is a liquid matrix for direct application to the skin surface. After the matrix is ​​applied to the skin, it spontaneously changes color according to the skin's pH and achieves differentiated sustained release and retention.

10. The application according to claim 8, characterized in that, The topical skin care preparation is a serum, lotion, or spray.

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