Three previously undescribed indole alkaloids from the fruits of Brucea javanica (L.) Merr. with their tyrosinase inhibitory activity.

Brucea javanica (L.) Merr. (Simaroubaceae) is a widely recognized medicinal plant in traditional Chinese medicine, noted for its rich variety of structurally diverse secondary metabolites. As part of our ongoing phytochemical investigation on the fruits of this species, three undescribed indole alkaloids, named Yadanziindoles A-C (1-3), were isolated and identified. Their structures were elucidated based on extensive spectroscopic data (HRESIMS, 1D and 2D NMR). Structurally, compounds 1 and 2 feature a C-2 2-hydroxypropan-2-yl substituent and differ in the oxidation state of the C-3 functionality, whereas compound 3 possesses a distinct, highly oxidized C-2 acyl side chain. In bioactivity assays, compounds 1 and 2 exhibited promising tyrosinase inhibitory activity. To gain deeper insights into the molecular basis of the observed activity, we conducted molecular docking studies to characterize their binding interactions with the target enzyme. These findings suggest that these indole derivatives represent a promising template for the development of novel tyrosinase inhibitors.