Discovery of Cycloneolignan Enantiomers from Isatis indigotica Fortune with Neuroprotective Effects against MPP+-Induced SH-SY5Y Cell Injury

Abstract A pair of new cycloneolignan enantiomers ( 1a and 1b ) were isolated from the leaves of Isatis indigotica Fortune. Their structures were elucidated by extensive spectroscopic data analysis, including 1D and 2D NMR, HRESIMS, MS/MS analysis, together with theoretical electronic circular dichroism (ECD) calculations. Compounds 1a and 1b were then evaluated for their neuroprotective effects against MPP + -induced SH-SY5Y cell injury. As a result, compounds 1a (77.64 %) and 1b (78.62 %) exhibited moderate neuroprotective activity at the concentration of 12.5 µ M compared with that of MPP + treated group (62.00% at 1mM) by MTT assay. Furthermore, Annexin V-FITC/PI analysis showed that apoptosis ratios of 1a and 1b were reduced to 10.99 % and 9.31 %, respectively.