Sterol-like natural products and other secondary metabolites with antimicrobial and antiplasmodial activities from Penicillium tanzanicum.

A recent review on Penicillium species highlighted steroids as a taxonomic marker of this genus. In the current study, three steroids (1-3), an acetophenone (4), and thirteen known compounds (5-17) were isolated from the solid culture of Penicillium tanzanicum, isolated from bull dung. The structures of the compounds were established using extensive spectroscopic and spectrometric analyses (NMR, HRMS) and by comparison with published data. The absolute configurations of steroids 1-3 were determined by electronic circular dichroism (ECD) calculations, confirming their identities as trestione (1), formestane (2), and oxandrolone (3). The crude extract exhibited moderate activity against Mycobacterium tuberculosis (MIC = 400 µg mL-1) and significant activity against Enterococcus faecalis and E. faecium (MIC = 50 µg mL-1). Compounds 8, 9, 11, and 13 displayed weak to moderate antibacterial and antimycobacterial activities against M. tuberculosis, Staphylococcus aureus, E. faecalis, and E. faecium, with MIC values ranging from 50 to 100 µg mL-1. Notably, compounds 1 and 2 demonstrated promising antiplasmodial activity against the multi-resistant Plasmodium falciparum (PfDd2) strain, with IC50 values of 26.58 and 15.03 µM, respectively, accompanied by low haemolytic effects. These findings underscore the potential of fungi from underexplored ecological niches as sources of new anti-infective leads warranting further optimisation and preclinical evaluation.