Inhibitory Effect of Gnetin C, a Resveratrol Dimer from Melinjo (<i>Gnetum gnemon</i>), on Tyrosinase Activity and Melanin Biosynthesis

Abstract

Tyrosinase is the key enzyme involved in melanogenesis. The aim of this study was to investigate the in vitro inhibitory effects of gnetin C, a resveratrol dimer isolated from melinjo (Gnetum gnemon) seeds, on tyrosinase activity and melanin biosynthesis in murine B16 cells. The inhibitory activities of gnetin C and resveratrol were shown to be almost equal against tyrosinase and melanin biosynthesis in the cells. The IC 50 values of gnetin C activity against tyrosinase and melanin biosynthesis were 7.0 and 7.6 µM, respectively, whereas resveratrol demonstrated IC 50 values of 7.2 and 7.3 µM, respectively. These results indicated that gnetin C inhibited melanogenesis, in a manner similar to that of resveratrol, by inhibiting tyrosinase and may therefore function as a new skin-whitening agent. However, the direct effects of gnetin C and resveratrol on murine tyrosinase activities were not equal. The IC 50 value of resveratrol was 10.1 µM, while gnetin C only exhibited a 25.2% enzyme inhibition at 16 µM. The IC 25 values for gnetin C and resveratrol were 15.5 and 4.0 µM, respectively. Therefore, it is suggested that the effects of gnetin C may be due to mechanisms other than the direct inhibition of tyrosinase activity.

Inhibitory Effects of Resveratrol on Melanin Synthesis in Ultraviolet B-Induced Pigmentation in Guinea Pig Skin

“…Depigmentation agents commonly have similar phenol-based structures, which can inhibit tyrosinase activity (Newton et al ., 2007). Resveratrol also has a phenol-based structure, and several in vitro studies have reported that resveratrol originated from various natural products, which inhibit melanin synthesis (Ohguchi et al ., 2003; Yanagihara et al ., 2012). Shin et al .…”

Isolation of Resveratrol from Vitis Viniferae Caulis and Its Potent Inhibition of Human Tyrosinase

“…Kim et al [29] reported that resveratrol inhibited murine TYR weakly (32.7% inhibition at 100  µ M or 22.8  µ g mL −1 ), but Yanagihara et al [30] reported that it is a potent inhibitor (IC50 = 10.1  µ M = 2.3  µ g mL −1 ). Only the latter study showed a dose-response curve and is, though, more reliable.…”

Natural Melanogenesis Inhibitors Acting Through the Down-Regulation of Tyrosinase Activity

“…Another interesting melanogenesis inhibitor is gnetin C (Figure 11c), which is a resveratrol dimer from Gnetum gnemon . Gnetin C inhibits melanogenesis by directly inhibiting tyrosinase activity and antioxidative properties [100]. In addition, two glycosides of hydroxylstilbene, including a glycoside of resveratrol, piceid (Figure 11d), from Polygonum cuspidatum [101] and a glycoside of oxyresveratrol, mulberroside A (Figure 11e), from Morus alba [102], were proven to inhibit melanogenesis through the down-regulation of the MITF protein.…”