Two new quassinoids and other constituents from Picrasma javanica wood, and their biological activities

Picrasma javanica Blume (Simaroubaceae) is a medium-sized tree that is distributed widely in tropical Asia. In our previous study, we isolated quassinoids from P. javanica bark collected in Myanmar, and reported their antiproliferative activities. In our ongoing research for the discovery of bioactive compounds from Myanmar medicinal plants, two new quassinoids, (16R)-methoxyjavanicin B (1) and (16S)-methoxyjavanicin B (2), along with seven known compounds (3–9), were isolated during the phytochemical investigation of the CHCl₃ soluble portion of the MeOH extract of P. javanica wood. The structures of the new compounds were elucidated by analyses of their spectroscopic data (1D- and 2D-NMR, HRESIMS, and CD). A cytotoxicity assay revealed that compound 8 showed moderate activities against all tested cancer cell lines, the human lung (A549), breast (MCF7), and cervical (HeLa), and the normal fibroblast cell line, with IC₅₀ values ranging from 48.6 to 65.9 μM. Furthermore, the antibacterial assay demonstrated that 1 and 2 had the highest activities (MIC value of 1.6 μM each), followed by 5 and 3 (MIC values of 3.1 and 6.3 μM, respectively) against the Gram-positive bacterium B. subtilis.