Discovery of New Triterpenoid Saponins Isolated from with Antifungal Activity against Rice Blast Fungus .

While searching for new antifungal compounds, we revealed that a methanol extract of plant species has a potent antifungal activity against rice blast fungus . To identify the antifungal substances, the methanol extract of was extracted by organic solvents, and consequently, six active compounds were isolated from the -butanol layer. The isolated compounds were five new acylated triterpenoid saponins including maejaposide I (), maejaposides C-1, C-2, and C-3 (-), and maejaposide A-1 (), along with a known one, maejaposide A (). These chemical structures were determined by NMR and a comparison of their NMR and MS data with those reported in the literature. Based on the antifungal bioassay, the five compounds (-) exhibited strong antifungal activity against with MIC values ranging from 4 to 32 μg/mL, except for maejaposide I () (MIC > 250 μg/mL). When the compounds were evaluated at concentrations of 125, 250, and 500 μg/mL for an antifungal activity against rice blast, compounds - strongly reduced the development of blast by at least 85% to 98% compared to the untreated control. However, compound did not show any antifungal activity up to a concentration of 500 μg/mL. Taken together, our results suggest that the methanol extract of and the new acylated triterpenoid saponins can be used as a source for the development of natural fungicides.