Three new polyhydroxy-chlorinated dibenzo-α-pyrones isolated from Helicosporium sexuale LZ15

Three new chlorine-substituted dibenzo-α-pyrone derivatives, helicochlorins A-C (1-3), together with three known congeners (4-6), were isolated from fermented rolled oats culture of Helicosporium sexuale LZ15. Helicochlorins A-C (1-3) share a polyhydroxy-chlorinated fused isocoumarin framework, characterized primarily by a chlorine substituent on the fused-ring system. The structures of the new compounds were unambiguously elucidated by comprehensive spectroscopic analyses (1D and 2D NMR, HRESIMS) and further confirmed through NOE correlations and ECD calculations. In addition, the crystal structure of compound 4 was determined for the first time. The cytotoxicity evaluation revealed that compound 2 exhibited weak activity against A549 cells, compound 5 showed weak activity against HepG2 cells, while compound 4 demonstrated weak cytotoxicity toward both A549 and HepG2 cell lines.