茯苓提取物对酪氨酸酶抑制动力学及刺激性研究

研究了茯苓提取物对酪氨酸酶单酚酶和二酚酶活力的影响及其抑制动力学,测试结果表明:茯苓提取物对酪氨酸酶单酚酶和二酚酶的活力均有抑制作用,单酚酶和二酚酶活力下降50%的茯苓提取物质量浓度(IC_(50))分别为0.008和0.040 g/L。酪氨酸酶单酚酶的催化反应存在迟滞时间,茯苓提取物对酪氨酸酶二酚酶活力的抑制作用表现为可逆效应。Lineweaver-Burk图显示茯苓提取物对二酚酶的作用表现为非竞争性与竞争性混合的抑制类型。在此基础上采用红细胞溶血实验初步评估茯苓提取物对皮肤的刺激性,结果显示含2.000 g/L茯苓提取物的样品无刺激性,质量浓度远大于单酚酶和二酚酶活力下降50%的茯苓提取物质量浓度IC_(50),茯苓提取物在0.200~0.800 g/L的质量浓度范围内可保证其安全添加且具有美白功效。

Tyrosinase activity inhibition kinetics and skin irritation of Poria cocos extract

The kinetics of inhibitory effect of Poria cocos extract on monophenolase and diphenolase activity of mushroom tyrosinase was studied. Test results show that Poria cocos extract efficiently inhibits both monophenolase and diphenolase activities of mushroom tyrosinase. Concentrations of Poria cocos extract leading to 50% activity lost (IC50) on monophenolase and diphenolase were calculated to be 0.008 and 0.040 g/L respectively. There is a lag time in the catalytic reaction process of the monophenolase. Inhibition of Poria cocos extract on activity of diphenolase of tyrosinase indicates a reversible effect. Lineweaver-Burk plots indicates that the inhibitor binds the enzyme reversibly other than reacts with it destructively. Lineweaver-Burk plots show that the inhibition type is a composite of competitive and non-competitive inhibition. On this basis, Poria cocos extract stimulus preliminary assessment was conducted with RBC hemolysis test, and results show that Poria cocos extract with a mass concentration of 2.000 g/L is non-stimulus while such concentration is far higher than IC50 of Poria cocos extract on monophenolase and diphenolase activity. It further indicates that Poria cocos extract displays whitening effect under the condition of the security. This suggests that Poria cocos extract with mass concentration range of 0.200~0.800 g/L is safe, for whitening cosmetic use.