Two novel aspochalasins, tricochalasin A (1) and aspochalasin A2 (2), along with three known compounds (3⁻5) have been isolated from the different culture broth of Aspergillus sp., which was found in the gut of a marine isopod Ligia oceanica. Compound 1 contains a rare 5/6/6 tricyclic ring fused with the aspochalasin skeleton. The structures were determined on the basis of electrospray ionisation mass spectroscopy (ESIMS), nuclear magnetic resonance (NMR) spectral data, and the absolute configurations were further confirmed by modified Mosher's method. Cytotoxicity against the prostate cancer PC3 cell line were assayed by the MTT method. Compound 3 showed strong activity while the remaining compounds showed weak activity.
Keywords: aspochalasin; cytotoxicity; gut fungus; tricyclic fused.