Strebluses E-H, four new stilbene-like derivatives from the stems of Streblus ilicifolius

Following bioactivity-guided isolation, four new stilbene-like derivatives, named Strebluses E-H, were isolated from the EtOAc-soluble fraction of the stems of Streblus ilicifolius (Moraceae). Their chemical structures were elucidated based on NMR spectroscopic data interpretation and optical rotation calculation. Streblus E possesses potent tyrosinase inhibitory activity with an IC₅₀ value of 0.1 μM. Oxy-tyrosinase has two bound Cu²⁺ ions and a peroxide group in the binding site, which has a role in the catalytic oxidation. Thus, a docking study of Streblus E with oxy-tyrosinase was performed to analyze the ligand-protein interactions. With in silico modelling, the S value and the ligand-protein interactions suggested that Streblus E showed lower binding affinity for oxy-tyrosinase than that of Streblus C.