Polyphenol carbon dots as well as preparation method and application thereof

Abstract

The invention relates to the technical field of carbon dots, in particular to a polyphenol carbon dot as well as a preparation method and application thereof. According to the method, the polyphenol carbon dots are prepared through solvothermal reaction, in the reaction process, crystal nucleuses slowly grow, and through uniform and stable environment control, a high-stability and low-defect nano structure, namely the polyphenol carbon dots, can be obtained. The polyphenol carbon dots prepared by the invention have broad-spectrum antioxidant activity, can remove various free radicals, also have a better antioxidant effect on the cellular level, have higher biological safety, and can be used for antioxidant treatment of oxidative stress related diseases.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon dots, and in particular to polyphenol carbon dots and a preparation method and application thereof. Background Art

[0002] Polyphenol natural products are widely found in the roots, seeds and fruits of plants. Based on their high biological reactivity, they are used in biomedical fields such as anti-oxidation, anti-inflammatory and anti-tumor. However, there are still certain limitations, such as fast metabolism. Polyphenol compounds usually exist in the form of small molecules and are rapidly metabolized in organisms. Even if they are absorbed, they will form other forms, such as glucuronic acid conjugates, which have much worse antioxidant effects than polyphenol raw materials. In addition, because phenolic hydroxyl groups can bind to proteins and destroy the function of proteins, the corresponding polyphenol compounds also have certain biological toxicity at a certain dose.

[0003] Therefore, how to change the drug dosage form, reduce the metabolic rate and alleviate biological toxicity based on polyphenol compounds is a technical problem that needs to be solved urgently. Summary of the invention

[0004] In view of this, the object of the present invention is to provide a polyphenol carbon dot and a preparation method and application thereof. The polyphenol carbon dots prepared by the present invention have high antioxidant activity and high biosafety, and have a slower metabolic rate than polyphenol natural products.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing polyphenol carbon dots, comprising the following steps:

[0007] The polyphenolic compound is dissolved in a solvent and then subjected to a solvothermal reaction to obtain the polyphenolic carbon dots; the temperature of the solvothermal reaction is 120 to 200° C. and the time is 4 to 15 hours.

[0008] Preferably, the polyphenol compounds include one or more of flavonoid polyphenols, phenolic acid polyphenols and tannic acid polyphenols.

[0009] Preferably, the flavonoid polyphenols include one or more of quercetin, dihydromyricetin and naringenin;

[0010] The phenolic acid polyphenols include caffeic acid and / or coumaric acid;

[0011] The tannic acid polyphenols include one or more of gallic acid, ellagic acid and tannic acid.

[0012] Preferably, when the polyphenol compound is tannic acid, the temperature of the solvent thermal reaction is 120-140° C. and the time is 6-8 hours.

[0013] Preferably, the concentration of the polyphenolic compound in the solvent is 1-10 mg / mL.

[0014] Preferably, after the solvothermal reaction is completed, it further includes centrifuging the obtained product liquid, dialyzing the obtained supernatant, and then freeze-drying to obtain polyphenol carbon dot powder.

[0015] Preferably, the cut-off molecular weight of the dialysis bag used for dialysis is 3000-4000 Da, and the dialysis time is 48-96 h.

[0016] Preferably, the rotation speed of the centrifugation is 10000-15000 r / min, and the centrifugation time is 20-30 min.

[0017] The present invention provides polyphenol carbon dots prepared by the preparation method described in the above solution, and the surface contains phenolic hydroxyl groups.

[0018] The present invention provides the application of the polyphenol carbon dots described in the above solution in the preparation of drugs for treating oxidative stress diseases.

[0019] The present invention provides a preparation method of polyphenol carbon dots, which includes the following steps: dissolving a polyphenolic compound in a solvent and then performing a solvothermal reaction to obtain the polyphenol carbon dots; the temperature of the solvothermal reaction is 120-200 °C, and the time is 4-15 h. The present invention uses a solvothermal reaction to prepare polyphenol carbon dots. During the reaction process, crystal nuclei grow slowly, and through a homogeneous and stable environment control, a nanostructure with high stability and low defects can be obtained, that is, polyphenol carbon dots.

[0020] Polyphenol carbon dots are carbon materials at the nanoscale, with a large specific surface area and a stable carbon skeleton structure. Their unique nanostructure makes them more difficult to be metabolized and degraded compared with polyphenolic small molecules. Small molecules are easily decomposed or metabolized in the body, while polyphenol carbon dots can maintain a longer half-life in the body due to the strength of their carbonized structure and smaller size, thereby reducing their metabolic rate.

[0021] In addition, the polyphenol carbon dots prepared by the present invention have broad-spectrum antioxidant activity, can scavenge a variety of free radicals, and also have good antioxidant effects at the cellular level, and have high biosafety, and can be used for antioxidant treatment of oxidative stress-related diseases.

[0022] Furthermore, different polyphenolic compounds can prepare different types of polyphenol carbon dots. When the polyphenolic compound is tannic acid (TA), the prepared polyphenol carbon dots have more prominent antioxidant ability and biosafety. Description of the Drawings

[0023] Figure 1Infrared spectra of TANDs prepared for TA and Example 1;

[0024] Figure 2 XPS full spectra (a), C 1s orbital sub-spectra (b) and O 1s orbital sub-spectra (c) of TANDs prepared for TA and Example 1;

[0025] Figure 3 Raman spectra of TANDs prepared for TA and Example 1;

[0026] Figure 4 XRD pattern of TANDs prepared in Example 1;

[0027] Figure 5 UV-Vis absorption spectra of TANDs prepared for TA and Example 1;

[0028] Figure 6 TEM images (a) and particle size distribution and Zeta potential diagrams (b) of TANDs prepared in Example 1;

[0029] Figure 7 UV-Vis absorption spectra (a) and ·OH scavenging percentage results diagrams (b) after adding TANDs prepared in Example 1 with different concentrations to methylene blue solution;

[0030] Figure 8 UV-Vis absorption spectra (a) and DPPH· scavenging percentage results diagrams (b) after adding TANDs prepared in Example 1 with different concentrations to DPPH solution;

[0031] Figure 9 Results diagrams of the protective effect of TANDs with different concentrations on cell oxidative damage;

[0032] Figure 10 Fluorescence images (a) and fluorescence intensity measurements (b) of ROS in cells;

[0033] Figure 11 TEM images (a) and particle size distribution diagrams (b) of TANDs prepared in Example 2;

[0034] Figure 12 UV-Vis absorption spectra (a) and ·OH scavenging percentage results diagrams (b) after adding TANDs prepared in Example 2 with different concentrations to methylene blue solution;

[0035] Figure 13 UV-Vis absorption spectra (a) and DPPH· scavenging percentage results diagrams (b) after adding TANDs prepared in Example 2 with different concentrations to DPPH solution;

[0036] Figure 14 TEM images (a) and particle size distribution diagrams (b) of the TANDs prepared in Example 3;

[0037] Figure 15 UV-visible absorption spectra (a) and graphs of the scavenging percentage results of ·OH (b) after adding TANDs prepared in Example 3 at different concentrations to methylene blue solution;

[0038] Figure 16 UV-visible absorption spectra (a) and graphs of the scavenging percentage results of DPPH· (b) after adding TANDs prepared in Example 3 at different concentrations to DPPH solution;

[0039] Figure 17 Graphs of the cytotoxicity assay results of the TANDs prepared in Example 1 (a) and TA (b) against HPAEpiC cells and the cytotoxicity assay results of the TANDs (c) and TA (d) against RAW264.7 cells. Detailed implementation manners

[0040] The present invention provides a preparation method of polyphenol carbon dots, comprising the following steps:

[0041] Dissolve the polyphenolic compound in a solvent and then carry out a solvothermal reaction to obtain the polyphenol carbon dots; the temperature of the solvothermal reaction is 120 - 200 °C, and the time is 4 - 15 h.

[0042] In the present invention, unless otherwise specified, the raw materials used are all well-known commercially available products in the art.

[0043] In the present invention, the polyphenolic compound preferably includes one or more of flavonoid polyphenols, phenolic acid polyphenols, and tannin polyphenols; the flavonoid polyphenols preferably include one or more of quercetin, dihydromyricetin, and naringenin; the phenolic acid polyphenols preferably include caffeic acid and / or coumaric acid; the tannin polyphenols preferably include one or more of gallic acid, ellagic acid, and tannic acid. Different types of polyphenolic compounds can prepare different types of polyphenol carbon dots.

[0044] The present invention does not make special limitations on the type of the solvent, and selects according to the type of the polyphenolic compound as long as it can completely dissolve the polyphenolic compound. In the present invention, a suitable solvent is selected according to the principle of similar compatibility. High-polarity polyphenols (such as gallic acid, tannic acid, etc.) are easily soluble in polar solvents (water, ethanol, etc.), while low-polarity polyphenols (such as resveratrol, coumarin, etc.) are easily soluble in non-polar solvents (chloroform). In the present invention, when the polyphenolic compound is tannic acid, the solvent is preferably water.

[0045] In the present invention, the concentration of the polyphenolic compound in the solvent is preferably 1 to 10 mg / mL. In specific embodiments, it can be 1 mg / mL, 3 mg / mL, 5 mg / mL, 7 mg / mL, 8 mg / mL or 10 mg / mL.

[0046] The present invention has no special requirements for the dissolution process, as long as a homogeneous solution can be formed.

[0047] In the present invention, the temperature of the solvothermal reaction is 120 to 200 °C, and the time is 4 to 15 h; in specific embodiments, the temperature of the solvothermal reaction can be 120 °C, 130 °C, 140 °C, 150 °C, 160 °C, 170 °C, 180 °C, 190 °C or 200 °C; the time of the solvothermal reaction can be 4 h, 6 h, 8 h, 10 h, 12 h, 13 h or 15 h.

[0048] In the present invention, when the polyphenolic compound is tannic acid, the temperature of the solvothermal reaction is preferably 120 to 140 °C, more preferably 140 °C, and the time of the solvothermal reaction is preferably 6 to 8 h, more preferably 8 h. When the polyphenolic compound is tannic acid, the antioxidant ability and biosafety of the prepared polyphenol carbon dots are more prominent.

[0049] In the present invention, the solvothermal reaction is preferably carried out in a reaction kettle; the volume of the solution formed after the dissolution of the polyphenolic compound is preferably not more than 2 / 3 of the inner volume of the reaction kettle liner.

[0050] In the process of the solvothermal reaction of the present invention, the polyphenolic compounds continuously undergo dehydration condensation to form carbon nuclei, forming carbon dots with phenolic hydroxyl characteristic groups on the surface.

[0051] In the present invention, after the solvothermal reaction is completed, the present invention preferably includes centrifuging the obtained product liquid, and the obtained supernatant is dialyzed and then freeze-dried to obtain polyphenol carbon dot powder.

[0052] In the present invention, the rotation speed of the centrifugation is preferably 10000 to 15000 r / min, and the time of the centrifugation is preferably 20 to 30 min; in specific embodiments, the rotation speed of the centrifugation can be 10000 r / min, 13000 r / min or 15000 r / min, and the time of the centrifugation can be 20 min, 25 min or 30 min.

[0053] In the present invention, the cut-off molecular weight of the dialysis bag used for dialysis is preferably 3000 - 4000 Da; in specific embodiments, it can be 3000 Da, 3500 Da or 4000 Da. The dialysis time is preferably 48 - 96 h; in specific embodiments, the dialysis time can be 48 h, 55 h, 60 h, 70 h, 80 h, 90 h or 96 h. In the present invention, the dialysis solution used for dialysis is preferably deionized water.

[0054] In the present invention, low molecular weight impurities remaining in the synthesis process, such as solvents, reaction intermediates or unreacted precursors, etc., are removed by dialysis. These impurities may affect the purity, stability and biocompatibility of the final product.

[0055] There are no special requirements for the freeze-drying in the present invention, and the well-known freeze-drying process in the art can be adopted.

[0056] The preparation method of the present invention is simple, has good repeatability, mild conditions, low reaction temperature and short time, and can save energy compared with the long-time reaction under high temperature conditions.

[0057] The present invention provides polyphenol carbon dots prepared by the preparation method described in the above scheme, and the surface contains phenolic hydroxyl groups.

[0058] In the present invention, the particle size of the polyphenol carbon dots is preferably 1 - 15 nm.

[0059] The polyphenol carbon dots prepared by the present invention have broad-spectrum antioxidant activity, can scavenge a variety of free radicals, and also have good antioxidant effects at the cellular level, and have high biological safety, and can be used for antioxidant treatment of oxidative stress-related diseases.

[0060] The present invention provides the application of the polyphenol carbon dots described in the above scheme in the preparation of drugs for treating oxidative stress diseases. The oxidative stress diseases can be inflammatory diseases caused by oxidative stress or acute liver and kidney injury diseases caused by oxidative stress.

[0061] The following combines examples to elaborate in detail on the polyphenol carbon dots provided by the present invention, their preparation methods and applications, but they cannot be construed as limiting the protection scope of the present invention.

[0062] Example 1

[0063] Dissolve 1.5 g of tannic acid powder in 30 mL of deionized water, add the dissolved homogeneous solution to the reaction kettle, and ensure that the liquid volume does not exceed 2 / 3 of the inner lining volume. After installing the hydrothermal reaction kettle, place it in the oven and react at 140 °C for 8 h, and naturally cool to room temperature. Take out the solution, centrifuge at 10000 r / min for 20 min and take the supernatant. Dialyze with a dialysis bag with a cut-off molecular weight of 3500 for 48 h, and obtain TANDs powder by freeze-drying.

[0064] Example 2

[0065] Dissolve 1.5 g of tannic acid powder in 30 mL of deionized water. Add the homogeneous solution after dissolution to the autoclave, ensuring that the liquid volume does not exceed 2 / 3 of the inner lining volume. After installing the hydrothermal autoclave, place it in the oven and react at 140 °C for 6 h, then naturally cool to room temperature. Take out the solution, centrifuge at 10,000 r / min for 20 min, and take the supernatant. Dialyze with a dialysis bag with a molecular weight cut-off of 3500 for 48 h, and obtain TANDs powder through freeze-drying.

[0066] Example 3

[0067] Dissolve 1.5 g of tannic acid powder in 30 mL of deionized water. Add the homogeneous solution after dissolution to the autoclave, ensuring that the liquid volume does not exceed 2 / 3 of the inner lining volume. After installing the hydrothermal autoclave, place it in the oven and react at 120 °C for 6 h, then naturally cool to room temperature. Take out the solution, centrifuge at 10,000 r / min for 20 min, and take the supernatant. Dialyze with a dialysis bag with a molecular weight cut-off of 3500 for 48 h, and obtain TANDs powder through freeze-drying.

[0068] Structure and property characterization of Example 1

[0069] FT-IR characterization:

[0070] FT-IR analysis was performed on tannic acid (TA) and TANDs prepared in Example 1, and the results are as Figure 1 shown. It can be seen from Figure 1 the FT-IR spectrum of TA that a significant broad peak appears at 3000 - 3500 cm -1 , which is attributed to the strong interaction between a large number of phenolic hydroxyl groups in the TA molecule. The stretching vibration peak of C=O is at 1720 cm -1 , and the characteristic absorption peaks of the benzene ring are between 1400 - 1600 cm -1 . The FT-IR spectrum of TANDs is basically the same as that of TA, indicating that after hydrothermal treatment, TANDs still retain the functional groups and characteristic groups of TA.

[0071] XPS characterization:

[0072] XPS analysis was performed on TA and TANDs prepared in Example 1, and the results are shown in Figure 2 , Figure 2Among them, (a) is the XPS full spectrum, (b) is the C1s orbital partial spectrum, and (c) is the O 1s orbital partial spectrum. It can be clearly seen from the XPS full spectrum that there are mainly two peaks, which are attributed to C1s and O1s respectively. In TA, the proportion of O element is 31.5%, the proportion of C element is 68.5%, and O / C = 0.46. While in TANDs, the proportion of O element is 25.7%, the proportion of C element is 74.3%, and O / C = 0.35. The decrease of O / C indicates that there is a certain degree of dehydration carbonization during the formation of TANDs after hydrothermal treatment. Similarly, it can also be seen from the C1s and O1s partial spectra that the content of C-O decreases significantly, that is, during the hydrothermal process, dehydration carbonization occurs between molecules, and the content of -OH decreases significantly.

[0073] Raman characterization:

[0074] Raman analysis was performed on TA and TANDs prepared in Example 1, and the results are shown in Figure 3 . Figure 3 Among them, the D peak at 1340 cm -1 is related to the defects of the carbon atom lattice, and is attributed to the presence of SP 3 or SP 2 hybridized defective carbon. The G peak at 1580 cm -1 represents the in-plane stretching vibration of carbon atoms with SP 2 hybridization. The peak intensity ratio (ID / IG) is used to describe the intensity relationship between the D peak and the G peak. To a certain extent, it explains the defect situation in the carbon atom crystal. It can be clearly seen from Figure 3 that the D peak of TANDs is significantly stronger than that of TA, and ID / IG increases from 0.87 to 1.27, which is attributed to the occurrence of dehydration carbonization during the hydrothermal process.

[0075] XRD characterization:

[0076] XRD analysis was performed on TANDs prepared in Example 1, and the results are shown in Figure 4 . It can be seen from Figure 4 that TANDs have a broad peak at about 20°, indicating that TANDs have an amorphous structure.

[0077] Ultraviolet-visible absorption spectrum:

[0078] Ultraviolet-visible absorption spectrum analysis was performed on TA and TANDs prepared in Example 1, and the results are shown in Figure 5 . It can be seen from Figure 5 that TA has a characteristic absorption peak of flavonoid band II at about 300 nm. As the wavelength increases, the absorbance gradually decreases, because of the conjugation effect of the C ring. While the characteristic peak of TANDs undergoes a blue shift, and the peak shoulder is significantly steeper, and the decrease in absorbance is obvious, indicating that the hydrothermal process promotes the structural change of TA, and the conjugation degree of the C ring is significantly weakened.

[0079] Morphology, particle size distribution and Zeta potential of TANDs:

[0080] TEM observation was carried out on the TANDs of Example 1, and the results are shown in Figure 6 (a), and the particle size distribution and Zeta potential are shown in Figure 6 (b). From Figure 6 it can be seen that the TANDs prepared in Example 1 are evenly distributed without obvious aggregation phenomenon, and the particle size is 6.1 ± 1.1 nm. The zeta potential results show that TANDs are negatively charged with a potential value of -35 mV.

[0081] Determination of antioxidant capacity:

[0082] (1) Scavenging effect on hydroxyl radicals

[0083] The scavenging ability of TANDs for ·OH was tested by the fading effect of methylene blue (MB). The aqueous solution of MB is blue and has a characteristic absorption at 665 nm. When ·OH exists in the system, MB will be oxidized and the blue color gradually fades. After adding TANDs to the system, the degree of blue fading is significantly inhibited. As the concentration of TANDs increases, the absorbance at 665 nm gradually increases, as shown in Figure 7 (a), indicating that a large amount of ·OH is scavenged by TANDs, so that it cannot oxidize MB and cause it to fade. When the dosage of TANDs is 100 μg / mL, the scavenging rate for ·OH is close to 40%, and the ·OH scavenging rate of different concentrations of TANDs shows a concentration-dependent relationship, as shown in Figure 7 (b). Specifically, when the concentration of TANDs is 12.5, 25, 50 and 100 μg / mL, the scavenging rates for ·OH are 10.8%, 13.2%, 20.1% and 25.6% respectively.

[0084] (2) Scavenging effect on DPPH radicals

[0085] The scavenging ability of the TANDs prepared in Example 1 for reactive nitrogen radicals was investigated. 1,1-Diphenyl-2-picrylhydrazyl (DPPH) is a typical reactive nitrogen radical. As Figure 8 shown in (a), with the addition of TANDs, the lone pair electrons at the DPPH· center are neutralized, the purple color gradually fades, and the characteristic absorption at 519 nm gradually decreases. When the dosage of TANDs is 10 μg / mL, the scavenging efficiency for DPPH· can reach about 90%, as shown in Figure 8In (b). When the concentrations of TANDs were 1.25 μg / mL, 2.5 μg / mL, 5 μg / mL, and 10 μg / mL, the scavenging rates of DPPH· were 19.7%, 40.3%, 78.5%, and 89.7% respectively.

[0086] (3) Determination of antioxidant capacity at the cellular level

[0087] Rosup reagent was used to induce oxidative stress in human alveolar epithelial cells HPAEpiC cells to explore the protective effect of TANDs prepared in Example 1 on cells under oxidative damage. First, different concentrations of Rosup were co-incubated with cells for 4 h to induce the oxidative stress response of cells. With the addition of TANDs, the cell viability was significantly improved. With the increase in the concentration of TANDs, the cell survival rate was also increased, as Figure 9 described. When the addition amount of TANDs was 0, the cell survival rate was 52.7%. When the addition amounts of TANDs were 1.5625 μg / mL, 3.125 μg / mL, 6.25 μg / mL, 12.5 μg / mL, 25 μg / mL, and 50 μg / mL respectively, the cell survival rates were 50.1%, 51.5%, 54.8%, 59.3%, 66.6%, 81.9% respectively. When the addition amount of TANDs was 100 μg / mL, the cell survival rate almost reached 100% (specifically 95.8%), indicating that TANDs can effectively scavenge the reactive oxygen species (ROS) induced by Rosup, relieve oxidative damage, and improve the cell survival rate.

[0088] In order to visually observe the scavenging of intracellular ROS by TANDs, 2,7-dichlorofluorescein diacetate (DCFH-DA) was used to fluorescently stain the cells in the present invention. ROS in the system can oxidize DCFH-DA to generate 2',7'-dichlorofluorescein (DCF) and emit green fluorescence. The deeper the degree of oxidative stress of the cells, the more ROS are produced, and the stronger the green fluorescence. The present invention was divided into four groups, specifically, Control: blank group; TANDs: blank cells, added with TANDs for incubation; Rosup: model group, added with Rosup to establish a model; TANDs+Rosup: treatment group added with TANDs after modeling. As Figure 10 shown in (a) (the scale in the figure is 20 μm), the green fluorescence was obvious in the cells of the Rosup treatment group; while after the addition of TANDs, the generation of ROS was effectively inhibited, and the fluorescence was greatly weakened. By quantitatively measuring the fluorescence intensity of the above-mentioned groups of cells by flow cytometry, it can also be seen that the ROS scavenging effect of TANDs was obvious, as shown in Figure 10 (b) in 10. (b) in 10 is the data of flow cytometry, the ordinate represents the cell number, and the abscissa represents the fluorescence intensity.

[0089] Cytotoxicity test:

[0090] Different concentrations of TANDs and TA were added to HPAEpiC cells and RAW264.7 cells respectively. After incubation for 24 hours, the cell viability was tested. The results are shown in Figure 17 . From Figure 17 , (a) is the toxicity result of TANDs on HPAEpiC cells, (b) is the toxicity result of TA on HPAEpiC cells, (c) is the toxicity result of TANDs on RAW264.7 cells, and (d) is the toxicity result of tannic acid on RAW264.7 cells. From Figure 17 , it can be seen that the tannic acid carbon dots prepared by the present invention have lower biological toxicity than tannic acid and high biosafety.

[0091] Structure and performance characterization of Example 2

[0092] Morphology and particle size distribution of TANDs:

[0093] TEM observation was carried out on the TANDs of Example 2. The results are shown in Figure 11 (a), and the particle size distribution is shown in Figure 11 (b). From Figure 11 , it can be seen that the TANDs prepared in Example 2 are evenly distributed without obvious aggregation phenomenon, and the particle size is 6 nm.

[0094] Determination of antioxidant capacity:

[0095] (1) Scavenging effect on hydroxyl radicals

[0096] Referring to the method of Example 1, the scavenging ability of the TANDs prepared in Example 2 for ·OH was tested. The results are shown in Figure 12 , where (a) is the ultraviolet-visible absorption spectrum after adding different concentrations of TANDs to methylene blue solution, and (b) is the scavenging percentage of ·OH. From Figure 12 , it can be seen that after adding TANDs to the system, the degree of blue fading is significantly inhibited. As the concentration of TANDs increases, the absorbance at 665 nm gradually increases, as shown in Figure 12 (a), indicating that a large amount of ·OH is scavenged by TANDs, so that it cannot oxidize MB and cause it to fade. When the dosage of TANDs is 6.25 μg / mL, 12.5 μg / mL, 25 μg / mL, 50 μg / mL and 100 μg / mL, the scavenging rates for ·OH are 0.4%, 0.8%, 1.9%, 4.1% and 9% respectively, as shown in Figure 12 (b).

[0097] (2) Scavenging effect on DPPH radicals

[0098] The scavenging effect of the TANDs prepared in Example 2 on DPPH radicals was tested by referring to the method of Example 1, and the results are shown in Figure 13 . As Figure 13 shown in (a) of Figure 13 , with the addition of TANDs, the lone pair electrons at the center of DPPH· were neutralized, the purple color gradually faded, and the characteristic absorption at 519 nm gradually decreased. When the dosages of TANDs were 0.39 μg / mL, 0.78 μg / mL, 1.56 μg / mL, 3.125 μg / mL, and 6.25 μg / mL, the scavenging rates for DPPH· were 11.4%, 21.7%, 40.4%, 58.6%, and 81.4% respectively, as shown in

[0099] Structure and property characterization of Example 3

[0100] Morphology and particle size distribution of TANDs:

[0101] The TANDs of Example 3 were observed by TEM, and the results are shown in Figure 14 (a) of Figure 14 , and the particle size distribution is shown in Figure 14 (b) of

[0102] . It can be seen that the TANDs prepared in Example 3 were evenly distributed without obvious aggregation phenomenon, and the particle size was 7 nm.

[0102] Determination of antioxidant capacity:

[0103] (1) Scavenging effect on hydroxyl radicals

[0104] The scavenging ability of the TANDs prepared in Example 3 on ·OH was tested by referring to the method of Example 1, and the results are shown in Figure 15 , where (a) is the ultraviolet-visible absorption spectrum after adding different concentrations of TANDs to the methylene blue solution, and (b) is the scavenging percentage of ·OH. As Figure 15 can be seen, after adding TANDs to the system, the degree of blue fading was significantly inhibited. As the concentration of TANDs increased, the absorbance at 665 nm gradually increased, as shown in Figure 15 (a) of Figure 15 , indicating that a large amount of ·OH was scavenged by TANDs and thus could not oxidize MB and cause it to fade. When the dosages of TANDs were 6.25 μg / mL, 12.5 μg / mL, 25 μg / mL, 50 μg / mL, and 100 μg / mL, the scavenging rates for ·OH were 0.8%, 1.7%, 3.8%, 7.1%, and 10.6% respectively, as shown in Figure 15 (b) of

[0105] (3) Scavenging effect on DPPH radicals

[0106] The scavenging effect of the TANDs prepared in Example 3 on DPPH radicals was tested according to the method of Example 1, and the results are shown in Figure 16 . As Figure 16 shown in (a) of Figure 16 , with the addition of TANDs, the lone pair electrons at the center of DPPH· were neutralized, and the purple color gradually faded, and the characteristic absorption at 519 nm gradually decreased. When the dosages of TANDs were 0.39 μg / mL, 0.78 μg / mL, 1.56 μg / mL, 3.125 μg / mL, and 6.25 μg / mL, the scavenging rates for DPPH· were 13.7%, 39.9%, 72.8%, 87.9%, and 90.4% respectively, as shown in

[0107] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can still be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing polyphenol carbon dots, characterized in that: The following steps are involved: The polyphenolic compound is dissolved in a solvent and then subjected to a solvothermal reaction to obtain the polyphenolic carbon dots; the temperature of the solvothermal reaction is 120 to 200° C. and the time is 4 to 15 hours.

2. The preparation method according to claim 1, characterized in that The polyphenol compounds include one or more of flavonoid polyphenols, phenolic acid polyphenols and tannic acid polyphenols.

3. The preparation method according to claim 2, characterized in that: The flavonoid polyphenols include one or more of quercetin, dihydromyricetin and naringenin; The phenolic acid polyphenols include caffeic acid and / or coumaric acid; The tannic acid polyphenols include one or more of gallic acid, ellagic acid and tannic acid.

4. The preparation method according to claim 3, characterized in that: When the polyphenol compound is tannic acid, the temperature of the solvent thermal reaction is 120-140° C. and the time is 6-8 hours.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The concentration of the polyphenols in the solvent is 1-10 mg / mL.

6. The preparation method according to claim 1, characterized in that: After the solvothermal reaction is completed, the obtained product liquid is centrifuged, and the obtained supernatant is dialyzed and freeze-dried to obtain polyphenol carbon dot powder.

7. The preparation method according to claim 6, characterized in that: The molecular weight cutoff of the dialysis bag used for the dialysis is 3000-4000Da, and the dialysis time is 48-96h.

8. The preparation method according to claim 6, characterized in that: The centrifugal speed is 10000-15000 r / min, and the centrifugal time is 20-30 min.

9. The polyphenol carbon dots prepared by the preparation method according to any one of claims 1 to 8 contain phenolic hydroxyl groups on the surface.

10. Use of the polyphenol carbon dots according to claim 9 in preparing drugs for treating oxidative stress diseases.

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