Uvarmicranones A and B, two new benzoquinones and cytotoxic constituents from the stems of Uvaria micrantha (A. DC.) Hook. f. & Thomson.

Two novel benzoquinones, uvarmicranones A (1) and B (2), along with 15 known compounds (3 − 17) were isolated from the stems of Uvaria micrantha (Annonaceae). Their structures were elucidated by analyses of NMR and high-resolution mass data. A plausible biosynthetic pathway of uvarmicranone A (1) via Diels-Alder cycloaddition reaction was also proposed. Some isolated compounds were evaluated for their cytotoxic activities. Compounds 1, 14, and 15 showed moderate cytotoxic effects against T-cell acute lymphoblastic cells (MOLT-3), with IC₅₀ values of 7.83 ± 0.83, 6.53 ± 1.01, and 4.20 ± 0.29 μM, respectively. Additionally, compound 15 exhibited moderate cytotoxicity against cervical carcinoma cells (HeLa) with an IC₅₀ value of 7.00 ± 3.15 μM. [ABSTRACT FROM AUTHOR]