Isolation and Characterization of Isofraxidin 7--(6'---Coumaroyl)--glucopyranoside from Thunberg: A Novel, Nontoxic Hyperpigmentation Agent That Is Effective In Vivo.

Abnormalities in skin pigmentation can produce disorders such as albinism or melasma. There is a research need to discover novel compounds that safely and effectively regulate pigmentation. To identify novel modulators of pigmentation, we attempted to purify compounds from a bioactive fraction of the Korean medicinal plant Thunberg. The novel compound isofraxidin 7--(6'---coumaroyl)--glucopyranoside (compound ) was isolated and its pigmentation activity was characterized in mammalian melanocytes. Compound stimulated melanin accumulation and increased tyrosinase activity, which regulates melanin synthesis. Moreover, compound increased the expression of tyrosinase and the key melanogenesis regulator microphthalmia-associated transcription factor (MITF) in melanocytes. Compared to the parent compound, isofraxidin, compound produced greater effects on these pigmentation parameters. To validate compound as a novel hyperpigmentation agent in vivo, we utilized the zebrafish vertebrate model. Zebrafish treated with compound showed higher melanogenesis and increased tyrosinase activity. Compound treated embryos had no developmental defects and displayed normal cardiac function, indicating that this compound enhanced pigmentation without producing toxicity. In summary, our results describe the characterization of novel natural product compound and its bioactivity as a pigmentation enhancer, demonstrating its potential as a therapeutic to treat hypopigmentation disorders.