(±)-Talaroindolenes A and B: Spiro-Ergot Alkaloid Enantiomers with a 5/6/6/6/5/5 Hexacyclic System and Cardioprotective Activity from Talaromyces sp. TJ403-AL05

Chemical investigation of fungus Talaromyces sp. TJ403-AL05 led to the isolation of (±)-talaroindolenes A ( 1a / 1b ) and B ( 2a / 2b ), two pairs of spiro-ergot alkaloid enantiomers featuring a 5/6/6/6/5/5 hexacyclic skeleton defined by a spiro[2-oxa-7,15-diaza-pentacyclo[12.2.1.1 1,8 .0 3,7 .0 12,18 ]octadecane-13,1′-[2]oxacyclopentane] core. Extensive spectroscopic analysis, X-ray crystallography and ECD calculation were used to determine the structure and absolute configuration of each enantiomer after chiral resolution. Additionally, 2b exhibited significant cardioprotective effect on oxygen-glucose deprivation (OGD)-damaged H9C2 cells by preserving mitochondrial membrane potential and modulating the mRNA levels of Bax and Bcl-2.