Abstract: To study the inhibitory effect of floridoside in red algae on the generation of melanin, the B16-F0 melanoma cells were used to evaluate the ability of floridoside on the biosynthesis of melanin. The effect of floridoside on the activity of tyrosinase was also detected for investigating the mechanism. Results indicated that floridoside showed no obvious toxicity to B16-F0 melanoma cells, but suppressed melanogenesis with the concentration dependence manner. Floridoside was discovered to inhibit both the monophenolase and the o-diphenolase activities. It influenced the steady state of monophenolase activity and IC50 was 89 mmol/L. The inhibition on o-diphenolase activity was in a concentration dependent manner, and 40 mmol/L floridoside reduced the steady state activity for 33.08%. The inhibition kinetics analyzed by Lineweaver-Burk plots showed that floridoside was a reversible competitive inhibitor, and the inhibition constant was determined to be 16.44 mmol/L for the free enzyme. In general, floridoside was potential to suppress the generation of melanin, and the mechanism was to inhibit the activity of tyrosinase, especially the activity of o-diphenolase.

Key words: floridoside, melanin, tyrosinase, inhibition