The previously detected antifungal activity against Mycosphaerella fijiensis of aqueous infusions of healthy banana (Musa acuminata cv. Grande Naine) leaves, suggested the production of phytoprotectants by the plant. The bioassay-guided VLC-purification of the lyophilized infusion of the leaves of 4-month old healthy banana (M. acuminata cv. Grande Naine) plants, resulted in the purification of a phytoanticipin with strong antifungal activity against M. fijiensis Morelet, the causal agent of black Sigatoka, the most destructive and devastating disease of bananas and plantains in the world. The LC-MS analysis of the purified phytoanticipin suggests a steroidal saponin structure with four sugar units attached to the C-3 position of a diosgenin-like aglycone. This represents the first report of phytoanticipins occurring in M. acuminata.