Isolation and Structural Elucidation of Sapogenins from Tupistra chinensis and Their Antifungal Acitivity Against Peronophythora litchii

The methanol extract of Tupistra chinensis showed antifungal acitivity against the sporangium germination of Peronophythora litchii.Bioassay-guided fractionation together with various chromatographic procedures(TLC,silica column chromatography,RP-18 reverse phase chromatography and Sephadex LH-20 gel chromatography)led to the isolation of two bioactive sapogenins from ethyl acetate phases of the methanol extract of T.chinensis.By means of spectroscopic analysis(MS,IR,1D NMR and 2D NMR),their structures were identified as 1β,2β,3β,4β,5β,7α-hexahydroxyspirost-25(27)-en-6-one(1) and spirost-25(27)-ene-1β,2β,3β,4β,5β,6β,7α-heptol(2).Bioassay in vitro revealed that the EC50 values of compounds 1 and 2 against sporangium germination of P.litchii were 100.28 mg·mL^-1 and 124.37 mg·mL^-1,respectively.Treatment with 500 mg·mL^-1 of compounds 1 and 2 before inoculated with P.litchi,the incidences of downy blight disease of the tested litchi fruits were just 16.7% and 18.9%.