Excessive production of melanin causes various dermatological disorders including hyperpigmentation. To search for anti-melanogenesis candidates from natural products, we discovered that leaves of Osmanthus fragrans var. aurantiacus (OFA) suppressed melanin production. The extract of OFA leaves and its fractions were subjected to bioactivity-guided separation by targeting active constituents and a total of four triterpenoids were obtained: 3α,24-dihydroxyurs-12-en-28 oic acid (1), pomolic acid (2), maslinic acid (3), and corosolic acid (4). Compounds 1 and 2 were isolated from this plant for the first time. All compounds were evaluated for their inhibitory activities against melanin production and tyrosinase activity. Active compounds were further investigated to understand their mechanisms of action. Results revealed that they significantly down-regulated TYRP-1 and TYRP-2 expression levels. Our results clarified the whitening property of this plant and provided evidence that active constituents of this plant possessed anti-melanogenesis effect and anti-tyrosinase activity for the first time.
Keywords: Anti-melanogenesis; Osmanthus fragrans var. aurantiacus; tyrosinase activity.