Secondary metabolites obtained from marine-derived fungi are rich sources of drug candidates. Three new sesquiterpenoids, chermesiterpenoids A–C (1–3), along with four known alkaloids (4–7), were isolated and identified from the marine red algal-derived fungus Penicillium chermesinum EN-480. The structures of these new sesquiterpenoids were elucidated using detailed analysis of the NMR data and their relative configurations were elucidated using nuclear overhauser effect spectroscopy (NOESY) spectra as well as gauge-independent atomic orbital (GIAO) NMR shift calculations and DP4+ probability analysis. Their absolute configurations were determined using electronic circular dichroism (ECD) calculations and modified Mosher’s method. Compounds 2 and 3 exhibited potent activities against human and aquatic pathogenic bacteria and plant pathogenic fungi.
