Novel Cyclic Hexapeptides from Marine-Derived Fungus, Aspergillus sclerotiorum PT06-1

Two novel cyclic hexapeptides containing both anthranilic acid and dehydroamino acid units, sclerotides A (1) and B (2), were isolated from the marine-derived halotolerant Aspergillus sclerotiorum PT06-1 in a nutrient-limited hypersaline medium. Both 1 and 2 are photointerconvertible and could be interconverted via a radical reaction Initiated by direct photoisomerization. Both compounds showed moderate antifungal activity. Compound 2 also showed weak cytotoxicity and antibacterial activity.