Bioactive cyclic peptides from the psychrotolerant fungus Penicillium algidum

A new cyclic nitropeptide, psychrophilin D (1), together with two known cyclic peptides, cycloaspeptide A (2) and cycloaspeptide D (3), were isolated from the psychrotolerant fungus Penicillium algidum using C-18 flash chromatography, LH-20 Sephadex and preparative HPLC. The structure of psychrophilin D (1) was derived from mass spectrometric information, ID and 2D NMR spectra and Marfey's method. The compounds were tested in antimicrobial, antiviral, anticancer and antiplasmodial assays. Psychrophilin D (1) exhibited a moderate activity (ID50 10.1 mug/ml) in the P388 murine leukaemia cell assay. Cycloaspeptide A (2) and D (3) exhibited moderate activity (IC50 3.5 and 4.7 mug/ml, respectively) against Plasmodium falciparum.