Antioxidant activity and neuroprotective effect of ethyl acetate fraction of Lonicera japonica on H2O2-induced oxidative stress

Abstract

Lonicera japonica are commonly used in herbal medicine for the antipyretic, detoxicant and anti-inflammatory actions. In this study, the in vitro antioxidant activity and neuronal protective effects of the ethyl acetate fraction of L. japonica (EFLJ) on H2O2-induced hippocampal HT22 and human neuroblastoma MC-IXC cells were evaluated. The 40% ethanolic extracts of L. japonica showed higher total phenolic and flavonoid contents than those of other ethanolic extracts. EFLJ showed higher 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) and 1,1-dphenyl-2-picrlhydrazyl (DPPH) radical scavenging activities than those of other fractions. EFLJ exhibited significant antioxidant activity, as determined by ferric reducing/antioxidant power (FRAP) assay, and showed inhibitory effects on malondialdehyde (MDA) production. EFLJ inhibited acetylcholinesterase (AChE) activity. In addition, EFLJ inhibited the production of reactive oxygen species and increased cell viability in H2O2-induced HT22 and MC-IXC cells, as determined by 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) and 2’,7’- dichlorofluorescein diacetate (DCF-DA) assays. The main phenolic compounds in EFLJ identified by ultra-high performance liquid chromatography-quadrupole time of flight/mass spectrometry (UPLC-QTOF/MS) were chlorogenic acid, quercetin pentoside, luteolin-7-glucoside, 3,4-dicaffeoylquinic acid, 1,3-dicaffeoylquinic acid and 1,4- dicaffeoylquinic acid. These results suggested that EFLJ includes various compounds with considerable antioxidant activity and neuronal protective effects against oxidative stress-induced cellular cytotoxicity. Therefore, EFLJ is a valuable functional food material for the prevention and improvement of neurodegenerative disorders.