Antifungal saponins from bulbs of white onion, Allium cepa L.

► Three new spirostanol saponins named ceposides A-C were isolated from white onion. ► Antimicrobial activity of ceposides were tested on ten fungal species. ► The activity increased with ceposide concentration. ► The activity varied with the following rank: ceposide B > ceposide A ∼ceposide C. ► Significant synergism was found for ceposides against Botrytis and Trichoderma.