1H- and 13C-nmr assignments of phyllanthin and hypophyllanthin: lignans that enhance cytotoxic responses with cultured multidrug-resistant cells
Somanabandhu, A.; Nitayangkura, S.; Mahidol, C.; Ruchirawat, S.; Likhitwitayawuid, K.; Shieh, H.L.; Chai, H.; Pezzuto, J.M.; Cordell, G.A.
Journal of Natural Products 56(2): 233-239
Phyllanthus amarus [P. niruri] is traditionally used to treat jaundice, and other diseases. Phyllanthin and hypophyllanthin were isolated from the aerial parts (collected from Bangkok and Mahidol University, Thailand), and complete 1H and 13C NMR data for these compounds are presented. Neither of these lignans demonstrated significant cytotoxic activity when evaluated with a battery of cultured mammalian (including human) cells, but phyllanthin and hypophyllanthin enhanced the cytotoxic response mediated by vinblastine (1 micro g/ml) against multidrug-resistant KB cells (ED50 values decreased from 9.0 to 2.1, and from >20 to 3.8 micro g/ml, respectively). In addition, phyllanthin was found to displace the binding of vinblastine with membrane vesicles derived from this cell line, suggesting an interaction with the P-glycoprotein.