New cytotoxic prenylated isoflavonoids from Bituminaria morisiana

Using cytotoxicity against KB cancer cells as a lead, bioguided-fractionation of the petroleum ether and ethyl acetate extracts of Bituminaria morisiana leaves led to the isolation of two new pterocarpans namely 3,9-dihydroxy-4-(3,3-dimethylallyl)[6aR,11aR]-pterocarpan, 3-hydroxy-4-(3,3-dimethylallyl)-4′′,5′′-dehydropyrano[8,9,2′′,3′′][6aR,11aR]-pterocarpan and one new isoflavone identified as 4′,5′′-dihydroxy-6′′-methoxy-4′′,4′′-dimethyl-4′′,5′′-dihydro-6′′H-pyrano[2′′,3′′,7,8]-isoflavone. Moreover, two known pterocarpans, erybraedin C and bitucarpin A, three known isoflavones, daidzein, 8-prenyldaidzein and bidwillon C, one known furanocoumarin, pseudoisopsoralen and one known coumestan, coumestrol were isolated. The structures of the isolated compounds were established by means of 1D and 2D NMR spectroscopy, as well as mass spectrometry. Further cytotoxicity tests against cells related to the immune system (Jurkat T, Mono-Mac-6 and polymorphonuclear cells) showed a moderate activity of the known pterocarpan erybraedin C against all cell lines used (IC50 values between 17.6 – 28.8 µM). In addition, erybraedin C was found to induce necrosis in leukaemia Jurkat T cells.