Abstract: A study on the inhibition type and mechanism was performed to screen the extract of G.inflata Bat. with the strongest inhibition effect on mushroom tyrosinase. The roots of G.inflata Bat. were extracted using different solvents sequentially. The inhibitory potencies and capacities of various extracts of G.inflata Bat., which were obtained from solvents including glycyrrhizic acid, waste liquid from glycyrrhizic acid extraction, petroleum ether extract, chloroform extract, ethyl acetate extract, n-butyl alcohol extract and water extract, toward mushroom tyrosinase with L-DOPA as the substrate were investigated. Radicals scavenging activity were examined using 2,2′-azino-bis(3-ethyl-benzothiazoline-6-sulfonic acid) diammonium salt(ABTS) radical cation(ABTS·﹢), hydroxyl radical(HO·) assay. The inhibition type on mushroom tyrosinase was obtained from Lineweaver-Burk plots. The inhibition mechanism on mushroom tyrosinase was explored combining its radicals scavenging ability. The results showed that the ethyl acetate extract had the strongest inhibitory capacity among seven extracts with IC50=3.4775 g/L, which also exhibited the strongest radical scavenging ability with IC50 of 0.0442 g/L for ABTS·+ and rate constant of 4.634×108 L/(g·s) for HO· scavenging reaction. There was a family of lines with a common intercept on the 1/v axis but with different slopes on Lineweaver-Burk plots with K1 value of 0.6667 g/L. In summary, the ethyl acetate extract is a reversible and competitive inhibitor, its inhibition mechanism on mushroom tyrosinase can be described as combining the capacity of scavenging oxygen free radicals with the ability of binding to the enzyme competitively.

Key words: G.inflata Bat., mushroom tyrosinase, ABTS radical cation, hydroxyl radical, competitive inhibition