Antimicrobial Polyketide Metabolites from Penicillium bissettii and P. glabrum

Screening of several fungi from the New Zealand International Collection of Microorganisms from Plants identified two strains of and , which exhibited antimicrobial activity against , and Further investigation into the natural products of the fungi, through extraction and fractionation, led to the isolation of five known polyketide metabolites, penicillic acid ( ), citromycetin ( ), penialdin A ( ), penialdin F ( ), and myxotrichin B ( ). Semi-synthetic derivatization of led to the discovery of a novel dihydro ( ) derivative that provided evidence for the existence of the much-speculated open-chained form of . Upon investigation of the antimicrobial activities of the natural products and derivatives, both penicillic acid ( ) and penialdin F ( ) were found to inhibit the growth of Methicillin-resistant . Penialdin F ( ) was also found to have some inhibitory activity against and along with citromycetin ( ).