A New Ursane-Type Triterpene from the Fermented Shallot Allium Ascalonicum

3,24-acetonideclethric acid (1), a new ursane-type triterpene, and four known compounds including ursolic acid (2), randiasaponin IV (3), ilekudinoside W (4) and (25S)-1β,3β,24β- trihydroxyspirost-5-en 1-O-α-L-rhamnopyranosyl-(1→2)- α-L-arabinopyranoside (5), and were isolated from the fermented shallot Allium ascalonicum. Their structures were determined by analysis of HR-ESI-MS, NMR spectral data, as well as comparison with those reported in the literature. All of the saponins (3-5) exhibited antimicrobial activity against three strains Staphylococcus aureus, Escherichia coli, and Candida albicans with IC₅₀ values in the range from 89.49 ± 2.24 to 95.71 ± 3.86 μM.