Aimon SomanabandhuSiriporn NitayangkuraChulabhorn MahidolSomsak RuchirawatKittisak LikhitwitayawuidHui Ling ShiehHeebyung ChaiJohn M. PezzutoGeoffrey A. CordellMahidol UniversityUniversity of Illinois at Chicago2018-08-102018-08-101993-01-01Journal of Natural Products. Vol.56, No.2 (1993), 233-23915206025016338642-s2.0-0027551488https://repository.li.mahidol.ac.th/handle/20.500.14594/22554Complete 1H-nmr data and unambiguous assignments of the 13C-nmr spectra of phyllanthin [1] and hypophyllanthin [2] were obtained through extensive nmr studies, including homonuclear COSY, homonuclear decoupling, APT, HETCOR, nOe difference, selective INEPT, and COLOC experiments. The absolute configuration of hypophyllanthin [2] was determined by cd. Neither of these lignans demonstrated significant cytotoxic activity when evaluated with a battery of cultured mammalian cells, but both were found to enhance the cytotoxic response mediated by vinblastine with multidrug-resistant KB cells. In addition, 1 was found to displace the binding of vinblastine with membrane vesicles derived from this cell line, suggesting an interaction with the P-glycoprotein. © 1993, American Chemical Society. All rights reserved.Mahidol UniversityBiochemistry, Genetics and Molecular BiologyChemistryMedicinePharmacology, Toxicology and PharmaceuticsArticleSCOPUS10.1021/np50092a008