鹅毛竹叶提取物抗氧化及酪氨酸酶抑制活性的研究

摘要

采用Folin试剂还原比色法、硝酸铝—亚硝酸钠比色法和香草醛—冰醋酸比色法测定鹅毛竹叶甲醇提取物及不同极性部位中总酚、总黄酮和三萜的含量，采用DPPH法、ABTS法、FRAP法评价各提取物的抗氧化能力及还原能力，同时采用酪氨酸酶催化氧化左旋多巴（L-DOPA）速率法体外测定酪氨酸酶活力。结果表明：鹅毛竹（Shibataea chinensis）叶乙酸乙酯相的总酚、总黄酮及三萜的含量最高，分别为（28.63±0.19）%、（23.74±0.17）%和（15.27±0.67）%；该相在不同抗氧化体系中的抗氧化活性最强，同时该相抑制酪氨酸酶的活性也最强，其半抑制浓度为3.29 mg/mL；鹅毛竹叶醇提物及其不同极相部位的总黄酮含量与还原力和DPPH、ABTS自由基的清除能力呈正相关，相关系数分别为0.9470、0.9001和0.9653，表明总黄酮是鹅毛竹叶提取物抗氧化活性的主要成分；总酚含量与酪氨酸酶抑制活性呈正相关，相关系数达到0.9910，表明总酚是鹅毛竹叶提取物抑制酪氨酸酶活性的主要成分；鹅毛竹叶乙酸乙酯相对酪氨酸酶的抑制作用及抗氧化活性最强，其对酪氨酸酶抑制机制为可逆的竞争性抑制，其抑制常数为27.49 mg/mL。%The inhibitory effect on tyrosinase and anti-oxidant activity of methanol extract and its different polarities (ethyl acetate, n-butyl alcohol, water) from leaves ofShibataea chinensis was studied. The contents of total phenols, total flavonoids, and triterpenoids in the extracts were detected by Forint reduction assay reagent, aluminum nitrate-sodium nitrite colorimetry, and vanillin-acetic acid assay. The antioxidative and reducing activities of extracts from leaves ofS. chinensis were assessed by DPPH, ABTS and FRAP. Tyrosinase activity was estimated by oxidation rate of L-dopa. The result showed that the contents of total phenols, total flavonoids and triterpenoids from leaves of S. chinensis were found the maximum in the ethylacetate, about 28.63%±0.19%, 23.74%±0.17% and 15.27%±0.67%, and had the best inhibitory effect on tyrosinase and antioxidant activity. Its 50% inhibiting concentration was estimated to be 3.29 mg/mL. In addition, positive correlation was existed between the total flavonoids content and the antioxidant ability to reducing power, DPPH• and ABTS for methanol extract and its polarities, with the correlation coefficient of 0.947, 0.9001 and 0.9653. It can be concluded that the total flavonoids content is a main component for the antioxidant activity of extracts from leaves ofS. chinensis. Meanwhile, positive correlation was existed between their total phenols content and the inhibitory effect on tyrosinase, with the correlation coefficient of 0.991, indicating that total phenols content is a main component for the inhibitory effect on tyrosinase. The ethylacetate extract fromS. chinensis is the best and a reversible competitive inhibitor for the oxidation of L-dopa and the anti-oxidant activity is also the best.