Carboxamide derivatives isolated from the endophytic fungus Diaporthe phaseolorum associated with Polygonatum cyrtonema Hua.

From the endophytic fungus Diaporthe phaseolorum associated with Polygonatum cyrtonema Hua, nine carboxamides were isolated, comprising five new compounds, phaseolorines A-E (1-3a, 4a, 6), along with four known compounds (3b, 5, 7, 8). Compounds 1-3 feature a rare 3-imidazolinozone structural unit, previously reported only once in metabolites of the fungus Xylariaceae sp. BSNB-0294. Compound 4a, a new phenylalanine derivative, was identified as the biosynthetic precursor to compounds 1-3. The structures of all isolates were unequivocally established through comprehensive 1D and 2D NMR, HR-ESI-MS, quantum chemical calculations, crystal X-ray diffraction, and chemical synthesis. When evaluated for anti-inflammatory activity in an LPS-induced RAW 264.7 macrophage model, compound 7 exhibited potent inhibition of NO production, with an IC50 value of 5.76 ± 0.76 μM.