| Using Pyricularia oryzae bioassay to search bioactive compounds, 16 compounds from Dioscorea deltoidea Wall var. orbiculata and 23 compounds from Tupistra wattii Hook. f. were obtained, and their structures were elucidated on the basis of physico-chemical and spectral methods.The 16 compounds from D. deltoidea Wall var. orbiculata are prosapogenin B of dioscin (1), prosapogenin A of dioscin (2), dioscin (3), orbiculatoside B (4)*, gracillin (5), protobioside (6), methyl protobioside (7), protodioscin (8), methyl protodioscin (9), protoneodioscin (10), methyl protoneodioscin (11), protogracillin (12), methyl protogracillin (13), protoneogracillin (14), methyl protoneogracillin (15) and orbiculatoside A (16)*, respectively. 4 and 16 are new compounds, 4, 6, 7 and 16 were isolated for the first time from D. deltoidea Wall var. orbiculata, and all the 16 compounds were isolated for the first time from Dioscorea genus.The 23 compounds from Tupista wattii Hook. f. are convallagenin B(1), kitigenin (2), neopentologenin (3), spirostane-1β, 2β, 3β, 4β, 5β, 6β-hexaol (4), wattigenin B (5)*, wattigenin C (6)*, convallagenin B 5-0-p-D-glucopyranoside (7), rhodexin A (8), wattoside F (9)*, wattoside G (10)*, wattoside H (11)*, wattoside I (12)*, wattoside J (13)*, wattoside B (14), methyl wattoside B (15), wattoside D (16), methyl wattoside D (17), wattoside K (18)*, methyl wattoside K (19)*, wattoside L (20)*, methyl wattoside L (21)*, wattoside M (22)* and methyl wattoside M (23)*, respectively. 8-10 are cardenolides, 1-6 are steroidal sapogenins, 7, 11-23 are steroidal saponins. 22 and 23 are a pair of furostanol saponins with sulphate group on the aglycone, and it is the first time to isolate such compounds from Tupistra genus. 5-61 9-131 18-23 are new compounds. 3-7,9-13,18-23 were isolated from Tupistra genus for the first time, 1-7, 9-13, 18-23 were isolated for the first time from Tupistra wattii Hook f.Among the 39 compounds, steroidal saponins from D. deltoidea Wall var. orbiculata showed potent activity against Pyricularia oryzae, however, thepolyhydroxylated steroidal sapogenins and saponins from Tupistra wattii Hook f. were inactive, except that the cardenolides had relatively very weak activity.According to the results of P. oryzae bioassay, MTT method was used to test the cytotoxic activity of these compounds on K562 cancer cell line. Steroidal saponins from D. deltoidea Wall var. orbiculata also showed strong cytotoxic activity, together with the cardenolides from T. wattii. And the other sapogenins and saponins from T. wattii were inactive. These results indicated that the activity against P. oryzae had some relationship with that of anticancer, and the P. oryzae bioassay was really an effective primary screening bioassay.Some compounds were selected for further investigation on other four cancer cell lines, according to the results of K562 cytotoxicity, and they showed activity and selectivity in the following tests. Methyl protobioside from D. deltoidea var. orbiculata was found to have the activity inducing apoptosis in HCT-15 cells, with the equal level to CDDP, and inhibit the cell cycle at G2/M phaseOn the basis of cytotoxic activity, the structure-activity relationship was discussed for the compounds from Dioscorea genus with similar aglycone structures. The results indicated that when the sugar chain was linked to C-3 position of aglycone, the terminal rhamnose linked to C-2 position of the inner glucose played crucial role to the cytotoxic activity.It is the first time to illustrate that the anticancer components from D. deltoidae var. orbiculata are the steroidal saponins, and the cardenolides from T. wattii are responsible for its antitumor activity as a folk medicine.
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