New antibacterial penicimenolide G with unusual 12-membered resorcylic acid lactone ring isolated from endophytic fungus Aspergillus giganteus

Abstract

Current antibiotics are increasingly losing their effectiveness against multidrug-resistant pathogenic bacteria, necessitating the search for new antibiotics. Endophytic fungi are widely recognized as valuable sources of structurally novel secondary metabolites with diverse biological activities. In this study, an endophytic fungus, designated KRL01, was isolated from a leaf of Capparis carandas. The strain was identified as Aspergillus giganteus through analysis of its internal transcribed spacer (ITS) rDNA sequence. Subsequently, the fungus was cultured in a rice medium and extracted using ethyl acetate. A novel metabolite, named penicimenolide G (1), was isolated from the extract using chromatography. Compound 1 demonstrated potent antibacterial activity against both Gram-positive and Gram-negative bacterial strains, including those resistant to the standard antibiotic amoxicillin.