A new pregnane glycoside from Dioscorea collettii var. hypoglauca

During further bioactivity-guided fractionation, a new pregnane glycoside, hypoglaucin G (1), and a known compound, pregna-5,16-dien-3 beta-ol-20-one 3-O-alpha-L-rhamnopyranosyl-(1-->2)-[alpha-L-rhamnopyranosyl-(1-->4)]-beta-D-glucopyranoside (2), were isolated from the EtOH extract of Dioscorea collettii var. hypoglauca rhizomes, which induced morphological deformation of Pyricularia oryzae mycelia with minimum morphological deformation concentration values of 135 mu M and 236 mu M, respectively. The structure of 1 was established as 16 beta-(4 '-methyl-5 '-O-beta-D-glucopyranosyl-pentanoxyl) 3-O-alpha-L- rhamnopyranosyl-(1-->2)-[alpha-L-rhamnopyranosyl-(1-->4)]-beta-D-glucoptranoside on the basis of chemical evidence and spectral analysis, especially by 2D NMR techniques.