Diacytochalasin A:A rearranged cytochalasin from endophytic fungus Diaporthe hongkongensis

Abstract

Four undescribed cytochalasins and ten known cytochalasins were isolated from the culture of Diaporthe hongkongensis, an endophytic fungus obtained from the leaves of Strychnos nux-vomica. Notably, diacytochalasin A (1) was the first cytochalasin discovered that features a unique 5/5/11 fused tricyclic ring system. The structures and absolute configurations of the four compounds were elucidated by performing comprehensive spectroscopic analyses and by examining their experimental and calculated electronic circular dichroism (ECD) spectra. These cytotoxic activities of 1–14 against five cancer cell lines, HGC-27, HCT-116, U87, MCF-7, and HepG2, were evaluated in vitro. Compounds 1, 3, 7, 9, 13, and 14 exhibited notable cytotoxicity to HGC-27 tumor cells with IC₅₀ values in the range of 0.1–3.59 μM.