Antibacterial phenolic compounds target GMPS from the endophytic Chaetomium grande -JPT2

Plant bacterial diseases threaten global food security and agricultural product quality. This study aimed to explore natural products with anti-phytopathogenic bacterial activity towards the new target guanosine monophosphate synthase (GMPS). Twelve phenolic compounds, including a new one, peniquinone L (1), were isolated using column chromatography and semipreparative HPLC from Chaetomium grande-JPT2. The molecular structures of the isolated compounds were determined by HRESIMS, 1D and 2D NMR spectrometry. High-throughput activity screening revealed that compound 11 could inhibit GMPS, yielding an EC50 value of 58.83 μg/mL. Molecular docking further revealed that the binding interaction between 11 and GMPS was primarily stabilised by two hydrogen bonds formed between the hydroxyl group in 11 and amino acid residues in GMPS. This is the first report on GMPS inhibition by phenolic compounds. Furthermore, compounds 4 and 7 displayed antibacterial activity against Xanthomonas axonopodis by two-fold serial dilution method, with MIC values of 100 μg/mL.