Cytotoxic and antimicrobial mycophenolic acid derivatives from an endophytic fungus Penicillium sp. MNP-HS-2 associated with Macrozamia communis

Macrozamia communis and its associated endophytic fungi are untapped sources of bioactive metabolites with great potential for medicinal exploitation. Chemical investigation of the mycelial extract derived from an endophytic fungus Penicillium sp. MNP-HS-2 associated with M. communis fruit offered four mycophenolic acid derivatives recognized as previously undescribed natural products (1-4) together with nine known metabolites (5-13). Chemical structures of isolated compounds were determined based on extensive spectroscopic analyses, including 1D/2D NMR and HRESIMS. The absolute stereochemistry of alternatain E (1) was unambiguously established by comparing its experimental and calculated time-dependent density functional theory electronic circular dichroism spectra (TDDFT-ECD). All isolated compounds were assessed for their antimicrobial and cytotoxic activities, where mycophenolic acid methyl ester (7) displayed significant cytotoxic activity against seven different cell lines with IC50 values in the low micromolar to nanomolar range, whereas mycophenolene A (3) exhibited a potent antibacterial activity against Staphylococcus aureus (MIC = 2.1 µg/mL).