Hyperpigmentation frequently occurs after inflammation from bacterial infection. Thus, the inhibition activity of tyrosinase, the key enzyme to catalyze the melanogenesis and/or inhibition of bacterial infection, could decrease melanin production. Hence, the potential inhibitors could be discovered from natural products. ω-Hydroxymoracin C (1), a new compound with two other 2-arylbenzofurans, i.e., moracin M (2) and moracin C (3), and two stilbenes, i.e., 3, 4, 3', 5'-tetrahydroxybibenzyl (4) and piceatannol (5), were isolated from the wood of Streblus taxoides. Compound 4 showed a strong inhibitory activity against tyrosinase enzyme with an IC50 value of 35.65 µg/mL, followed by compound 2 with an IC50 value of 47.34 µg/mL. Conversely, compound 1, 3 and 5 showed moderate activity, with IC50 values of 109.64, 128.67 and 149.73 µg/mL, respectively. Moreover, compound 1 and 3 showed an antibacterial effect against some Staphylococcus spp. Thus, the isolated compounds exhibited potential antityrosine and antibacterial effects. Additionally, an in silico study was performed in order to predict theoretical molecular interactions between the obtained metabolites from S. taxoides and tyrosinase as an extended in vitro enzyme binding assay experiment.
Keywords: Moraceae; Streblus taxoides; antibacterial activity; antityrosine activity; intracellular tyrosinase activity; melanin content.