牡丹花水提液清除羟自由基及抑制酪氨酸酶活性的研究

Study on scavenging effect on hydroxyl free radicals and inhibitory effect on tyrosinase of water extracts from peony

采用水提法提取牡丹花制得牡丹花水提液,以Fenton反应产生羟自由基,比色法检测牡丹花水提液清除羟自由基的能力,分别以L-酪氨酸和L-多巴为底物,在30℃,p H=6.8的磷酸盐缓冲体系中测定牡丹花水提液对酪氨酸酶单酚酶活性和二酚酶活性的抑制效应。实验结果表明,牡丹花水提液可有效清除羟自由基,牡丹花水提液质量浓度为1.00 g·L-1时,自由基清除率达91.67%;牡丹花水提液对酪氨酸酶单酚酶和二酚酶活性均有良好抑制作用,其IC50分别为0.015和0.210 g·L-1。牡丹花水提液对二酚酶的抑制作用表现为非竞争性抑制,米氏常数(Km)为0.4 mmol·L-1。

The water extract from the flowers of peony was prepared. Scavenging effect on hydroxyl free radicals,which were generated from the Fenton reaction of the water extracts was detected by spectrophotometry. The inhibitory action of water extracts from peony on the activity of monophenolase and diphenolase contained in tyrosinase were studied by using L- tyrosine and L- DOPA（ L- 3,4- dihydroxyphenylalanine） as substrate separately at 30 ℃ with Na2HPO4- Na H2PO4 as buffer solution（ p H = 6. 8）. The results showed that the water extracts from peony can scavenge hydroxyl free radicals effectively. The free radical elimination ratio of the water extracts achieves 91. 67% when the mass concentration of the peony water extract is 1. 00 g·L^-1. The water extract from peony displays good inhibitory effect to both monophenolase and diphenolase activity of tyrosinase with IC50 at 0. 015 g · L^-1for monophenolase and 0. 210 g · L^-1for diphenolase. The inhibition kinetics of the water extracts analyzed by Lineweaver- Burk plots demonstrated a non- competitive inhibitor for diphenolase and the Michaelis constant（ Km） was determined to be 0. 4 mmol·L^-1.