Triterpene Saponins from the Aerial Parts of Trifolium medium L. var.sarosiense

Seven previously unreported triterpene glycosides (1-7) were isolated from methanol extract of the aerial parts of Trifolium medium var. sarosiense (zigzag clover). Their structures were established by the extensive use of 1D and 2D NMR experiments along with ESI-MS and HRMS analyses. Compounds 1-7 are oleanane derivatives characterized by the presence of a keto group at C-22 of an aglycone and a primary alcoholic function at C-24 and differing functions at C-30. Among these, compounds 1-3 and 6 showed a secondary alcoholic function at C-11, which is methoxylated in compounds 4 and 7. Compound 5 was shown to possess a known aglycone, wistariasapogenol A; however, it is described here for the first time as a saponin constituent of the Trifolium genus. Some aspects of taxonomic classification of zigzag clover are also discussed.