Protective effects of lignin fractions obtained from grape seeds against bisphenol AF neurotoxicity via antioxidative effects mediated by the Nrf2 pathway

Lignin exhibits antioxidative and various other biological properties.However,its neuroprotection capability has rarely been studied.In this study,three types of lignin with different structures were prepared from grape seeds by using different isolation techniques.The antioxidative and neuroprotective effects of the lignin fractions were evaluated with the apoptosis model of murine neuroectodermal(NE-4C)neural stem cells stimulated with bisphenol AF.The results demonstrated that the half maximal inhibitory concentration for scavenging 2,2-diphenyl-1-picrylhydrazyl with water-soluble lignin(L-W,58.19μg·mL^(–1))was lower than those of lignin in the autohydrolyzed residue of grape seeds(84.27μg·mL^(–1))and original lignin in grape seeds(99.44μg·mL^(–1)).BPAF exposure had negative effects on the reactive oxygen species,malondialdehyde content,and superoxide dismutase and glutathione peroxidase activities in NE-4C cells,which can be reversed by using the prepared lignin to reduce oxidative stress.An immunofluorescence assay demonstrated that grape seed lignin induced protective effects on BPAF-injured NE-4C cells via the nuclear factor erythroid 2-related Factor 2 pathway.In addition,correlational analyses showed that lignin(L-W)with lower molecular weights and noncondensed phenolic hydroxyl group content and higher contents of COOH groups effectively prevented cell apoptosis,scavenged reactive oxygen species,and ensured protection from nerve injury.This study demonstrated that grape seed lignin can be used as a neuroprotective agent and serves as a demonstration of active lignin production from grape seed waste.