Novel anticancer agents, kayeassamins C-I from the flower of Kayea assamica of Myanmar.

A CHCl3-soluble fraction of 70% EtOH extract of the flower of Kayea assamica from Myanmar exhibited 100% preferential cytotoxicity (PC(100)) against human pancreatic cancer PANC-1 cells under nutrient-deprived conditions at 1 microg/mL. Bioassay-guided fractionation and isolation afforded nine new coumarins, kayeassamins A (8), B (9), and C-I (1-7), together with nine known coumarins (10-18). The structures of these compounds were identified by extensive spectroscopic techniques as well as by comparison with published data. Absolute configuration at C-1' of 1 was established as S-configuration by the modified Mosher method. All the isolates were evaluated for their in vitro preferential cytotoxicity using novel anti-austerity strategy. Among them, the novel coumarins, kayeassamins A (8), B (9), D (2), E (3), and G (5) exhibited the most potent preferential cytotoxicity (PC(100) 1 microM) in a concentration- and time-dependent manner and induced apoptosis-like morphological changes of PANC-1 cells within 24 h of treatment. Based on the observed cytotoxicity, structure-activity relationships have been established.