Seven known echinulin-related indolediketopiperazine alkaloids (1-7) were isolated from the Vietnamese sediment-derived fungus Aspergillus niveoglaucus. Using chiral HPLC, the enantiomers of cryptoechinuline B (1) were isolated as individual compounds for the first time. (+)-Cryptoechinuline B (1a) exhibited neuroprotective activity in 6-OHDA-, paraquat-, and rotenone-induced in vitro models of Parkinson's disease. (-)-Cryptoechinuline B (1b) and neoechinulin C (5) protected the neuronal cells against paraquat-induced damage in a Parkinson's disease model. Neoechinulin B (4) exhibited cytoprotective activity in a rotenone-induced model, and neoechinulin (7) showed activity in the 6-OHDA-induced model.
Keywords: 6-OHDA; Aspergillus niveoglaucus; NMR data; cryptoechinuline; cytotoxic activity; echinulin; neoechinulin; neuroprotective activity; paraquat; rotenone; urease inhibition.