库拉索芦荟中7种单体化合物对蘑菇酪氨酸酶活力的影响

Effects of Seven Compounds from Aloe barbadensis Mill on Activities of Mushroom Tyrosinase

目的研究库拉索芦荟中7种单体化合物对蘑菇酪氨酸酶催化氧化左旋多巴的活力的影响,并确定活性成分的抑制类型。方法以左旋多巴为底物,37℃条件下,以酶标仪记录反应体系在475 nm下光密度随时间的变化,通过相对酶活力比较加药后酶活力的变化,并通过Lineweaver-Burk曲线判定抑制类型,通过Dixon曲线求抑制常数。结果库拉索芦荟中的芦荟苦素具有很强的蘑菇酪氨酸酶抑制作用,且强于β-熊果苷,其50%抑制浓度(IC50)为108.6μg.mL-1,抑制类型为非竞争性抑制,抑制常数Ki=130.9μg.mL-1,而其余6种化合物的抑制作用较弱或没有抑制作用。结论芦荟苦素是库拉索芦荟中主要的蘑菇酪氨酸酶抑制成分。

Objective To evaluate the effects of seven compounds from Aloe barbadensis Mill on the activity of mush- room tyrosinase in the catalysis of levodopa, and to determine the inhibition type of active components. Methods Ty- rosinase activity was measured by the absorbance variations accompanying with the oxidation of the substrate levodopa which were recorded with a microplate reader at 475 nm under a constant temperature of 37 ℃. Inhibition type was de- termined by Lineweaver-Burk plot, and inhibition constant（Ki） was calculated by Dixon graphs. Results Aloesin was a strong noncompetitive inhibitor of mushroom tyrosinase and was more potent than arbutin, with an IC50 value of 108.6μg·mL-1 and a Ki value of 130.9μg·mL-1. The other compounds had weak activities or even had no activities. Conclu- sion Aloesin is the main mushroom tyrosinase inhibitor in Aloe barbctdensis Mill.