不同储存时间对普洱茶有机溶剂萃取物清除自由基活性的影响

Impact of Different Storage Time on Antioxidant Activity of Organic Solvent Extracts of Pu-erh Teas

本文以半数抑制浓度IC50的大小研究了十种茶叶（不同年份的生普和熟普）有机溶剂萃取物的体外抗氧化活性。结果表明，生茶有机溶剂萃取层清除DPPH自由基、羟基自由基、超氧自由基的IC50最小分别可达0.339 mg/mL、0.074 mg/mL、1.206 mg/mL，熟茶清除DPPH自由基、羟基自由基、超氧自由基的IC50最小分别可达0.554 mg/mL、0.164 mg/mL、1.927 mg/mL，生茶的抗氧化能力明显优于熟茶；各种普洱茶对自由基的清除能力主要取决于各萃取液中的多酚和黄酮含量。生茶乙酸乙酯层的茶多酚萃取量最多，在7.33-9.57%之间，正丁醇层的黄酮类物质的萃取量最多在7.08-10.99%之间，熟茶正丁醇层的茶多酚含量和黄酮类物质的含量在个有机溶剂层中均是最高的，分别在3.62-5.73%之间和4.75-5.83%之间，乙酸乙酯层和正丁醇层的萃取化合物具有较多的羟基，具有较强的清除自由基的能力;茶叶的储存时间对各萃取液的抗氧化能力无显著影响。

The antioxidant activity of different organic solvent extracts of pu-erh teas （raw and ripened pu-erh which produced in different years） was evaluated by half-inhibitory concentration （IC50）. Results showed that the IC50 value of raw teas to scavenge DPPH free radical and superoxide radical were 0.339 mg/mL, 0.074 mg/mL and 1.206 mg/mL, respectively. And the IC50 of ripe teas to the obove-mentioned radicals were 0.554 mg/mL, 0.164 mg/mL and 1.927 mg/mL, respectively. Raw teas had higher antioxidant activity than ripe ones. The extracts by different organic solvents showed different scavenging abilities to different free radicals, which depended on the content of tea polyphenol and flavonoids. The highest content of tea polyphenol in raw teas was extracted by ethyl acetate, ranged from 7.33% to 9.57% and the extract from butyl alcohol had the largest amount of flavonoids（7.08-10.99%）. For the ripe tea, the highest contents of tea polyphenol and flavonoids were 3.62% to 5.73% and 4.75% to 5.83%, respectively, which were all extracted by butyl alcohol. In conclusion, the extracts by ethyl acetate and butyl alcohol had higher capacity of scavenging free radicals due to the higher content of hydroxyl; and the storage time of teas showed little effect on the antioxidant activity from different extracts.