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 col
lettii var. hypoglauca rhizomes, which induced morphological deformation of
Pyricularia oryzae mycelia with minimum morphological deformation concentr
ation 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)]-bet
a-D-glucoptranoside on the basis of chemical evidence and spectral analysis
, especially by 2D NMR techniques.