Pencitrin and pencitrinol, two new citrinin derivatives from an endophytic fungus Penicillium citrinum salicorn 46

Two new citrinin derivatives, pencitrin (1) and pencitrinol (2), and a known compound citrinin (3), together with its two known dimers, penicitrinone A (4), penicitrinone E (5), were isolated from an endophytic fungus P. citrinum 46 derived from Salicornia herbacea Torr. by adding CuCl2 into fermentation medium. The structures of these compounds were elucidated by detailed spectroscopic analysis, and the absolute configurations of 1, 4, and 5 were determined by comparison of quantum chemical time-dependent density functional theory (TDDFT) calculated and electronic circular dichroism (ECD) spectra. Compound 1 exhibited potent cytotoxic activities towards A549 human lung cancer cells and HepG2 human liver cancer cells with IC50 values of 23.73 +/- 3.61 and 35.73 +/- 2.15 mu M, respectively, whereas compound 5 showed moderate cytotoxic activities towards A549 and HepG2 cancer cells with IC50 values of 40.47 +/- 4.52 and 53.57 +/- 3.24 mu M, respectively. The results from the current research highlighted the effectiveness and usefulness of the pipeline to discover novel bioactive fungal secondary metabolites by modification of the culture media.