Tyrosinase Inhibition Activities of Depsides Isolated from Ramalina Species

Abstract

Three depsides, namely sekikaic acid (1), homosekikaic acid (2), and 4′-O-demethylsekikaic acid (3) were isolated from acetone fraction of Ramalina spp. The structures were characterized by using spectroscopic techniques like 1H NMR, 13C NMR, ESI MS and IR. The quantitative determinations of these compounds were conducted by reversed phase high performance liquid chromatography with photodiode array detector (LC-PDA). The developed assay method could be considered as a suitable quality control method for Ramalina spp. The content on percentage dry basis of these compounds were 1.39%, 0.98% and 0.58% for compound 1, 2 and 3, respectively. It is the first time report for tyrosinase inhibition activity for depsides. All of these compounds exhibited inhibition for tyrosinase enzyme with the IC50 values 110.3±3.5, 90.1±1.4, and 206.4±5.1 µg/mL by the compounds 1, 2 and 3, respectively. The structure activity relationship of despides showed that the methoxy group at ring A might have enhanced the inhibitory activity. Therefore, these compounds may have their potential use in cosmetics with further studies.