Novel quercetin derivative of 3,7-dioleylquercetin shows less toxicity and highly potent tyrosinase inhibition activity

Abstract

Quercetin is a well-known plant flavonol and antioxidant; however, there has been some debate regarding the efficacy and safety of native quercetin as a skin-whitening agent via tyrosinase inhibition. Several researchers have synthesized quercetin derivatives as low-toxicity antioxidants and whitening agents. However, no suitable quercetin derivatives have been reported to date. In this study, a novel quercetin derivative was synthesized by the SN2 reaction using quercetin and oleyl bromide. The relationship between the structures and activities of quercetin derivatives as antimelanogenic agents was assessed using in vitro enzyme kinetics, molecular docking, and quenching studies; cell line experiments; and in vivo zebrafish model studies. Novel 3,7-dioleylquercetin (OQ) exhibited a low cytotoxic concentration level at >100 µg/mL (125 µM), which is five times less toxic than native quercetin. The inhibition mechanism showed that OQ is a competitive inhibitor, similar to native quercetin. Expression of tyrosinase, tyrosinase-related protein 1 (TRP-1) and tyrosinaserelated protein 2 (TRP-2), and microphthalmia-associated transcription factor was inhibited in B16F10 melanoma cell lines. mRNA transcription levels of tyrosinase, TRP-1, and TRP-2 decreased in a dose-dependent manner. Melanin formation was confirmed in the zebrafish model using quercetin derivatives. Therefore, OQ might be a valuable asset for the development of novel skinwhitening agents.