Entonalactams A–C: Isoindolinone derivatives from an Australian rainforest fungus belonging to the genus Entonaema

Bioassay-guided fractionation of an anti-malarial extract derived from the Australian rainforest fungus Entonaema sp. resulted in the isolation and characterisation of three new isoindolinone derivatives, entonalactams A–C. [Display omitted] •A unique Australian-sourced fungi collection was screened for antimalarial activity.•3 new isoindolinones (entonalactams A–C) and 3 known natural products were isolated.•The chemical structures of entonalactams A–C were determined via NMR/MS data analysis.•A single crystal X-ray structure for entonalactam A was obtained.•All isolated compounds exhibited low activity against Plasmodium falciparum at 50μM. Bioassay-guided fractionation of an antimalarial DCM/MeOH extract derived from the Australian rainforest fungus Entonaema sp. resulted in the isolation of three new isoindolinone derivatives, entonalactams A–C (1–3), along with the known natural products 3-methoxy-5-methylbenzene-1,2-diol (4), daldinal B (5), and ergosta-4,6,8(14),22-tetraen-3-one (6). The chemical structures of the new secondary metabolites were determined following extensive 1D/2D NMR and MS data analysis. A single crystal X-ray structure for entonalactam A (1) confirmed the NMR-based structure assignment. Entonalactams A–C (1–3) were all determined to be racemic based on chiro-optical data. All secondary metabolites were tested in vitro against Plasmodium falciparum malaria parasites, and ergosta-4,6,8(14),22-tetraen-3-one (6) was identified as the most active compound with 66% inhibition at 50μM.