Bioactive Alkaloids from the Mangrove-Derived Fungus SYSU-MS0024.

Chemical investigation of marine fungus SYSU-MS0024 cultured on solid-rice medium led to the isolation of three new alkaloids, including a pair of epimers, nigrosporines A () and B (), and a pair of enantiomers, (+)-nigrosporine C (+)-, and (-)-nigrosporine C (-)-, together with eight known compounds (-). Their structures were elucidated based on extensive mass spectrometry (MS) and 1D/2D nuclear magnetic resonance (NMR) spectroscopic analyses and compared with data in the literature. The absolute configurations of compounds - were determined by a combination of electronic circular dichroism (ECD) calculations, Mosher's method, and X-ray single-crystal diffraction technique using Cu Kα radiation. In bioassays, compound exhibited moderate inhibition on NO accumulation induced by lipopolysaccharide (LPS) on BV-2 cells in a dose-dependent manner at 20, 50, and 100 μmol/L and without cytotoxicity in a concentration of 100.0 μmol/L. Moreover, compound also showed moderate acetylcholinesterase (AChE) inhibitory activities with IC values of 103.7 μmol/L. Compound exhibited moderate antioxidant activity with EC values of 167.0 μmol/L.