Antifungal cyclic peptides from the terrestrial blue-green alga Anabaena laxa. I. Isolation and biological properties.

Laxaphycins are responsible for the antifungal and cytotoxic activity of crude ethanolic extracts from the cultured blue-green alga Anabaena laxa. These cyclic peptides exhibit an unusual biological synergism when tested for antifungal or cytotoxic effects. The isolation procedure for the peptides, their characterization and biological activities are described here along with experiments demonstrating synergism between the two major laxaphycins.