Picrajavanicins A-G, Quassinoids from Picrasma javanica Collected in Myanmar.

Seven new tetracyclic quassinoids, picrajavanicins A-G (1-7), along with three known analogues, were isolated from a CHCl3-soluble extract of the bark of Picrasma javanica collected in Myanmar. The structures of these compounds were elucidated using spectroscopic techniques, including 1D and 2D NMR. The absolute configuration at C-2 of 2 was determined to be S by the modified Mosher method. All the isolates were tested for their antiproliferative activities against a small panel of five human cancer cell lines. However, none of the isolated compounds exhibited inhibitory activity against any of the cancer cells used (IC50 values >10 μM).