Structure-activity relationships of anti-tyrosinase and antioxidant activities of cinnamic acid and its derivatives.

The related structure-activity relationships (SARs) of cinnamic acid and its derivates have not been studied in details yet. Herein, anti-tyrosinase and antioxidant activities of 18 compounds were evaluated. The results demonstrated that the substituents on the phenyl ring of cinnamic acid led to the enhancement of the inhibition on monophenolase and the weakening of the inhibition on diphenolase. Among these tested compounds, 9 was firstly discovered as a tyrosinase inhibitor in a reversible competitive manner with IC50 value of 68.6 ± 4.2 μM. Docking results demonstrated 9 located into the catalytic center of tyrosinase. Antioxidant assay indicated that only one hydroxyl group on the phenyl ring was not enough to possess the radical scavenging activity, and the number of hydroxyl groups may be more important. This study will be helpful for development of new cinnamic acid derivates as tyrosinase inhibitors and antioxidants with higher efficacy.