Chemical constituent and antioxidant activity of the husk of Chinese hickory

• Chemical constituent and antioxidant activity of the husk of Chinese hickory were investigated.
• Thirty-five phenolics, quinones and triterpenoids were isolated and identified.
• Some fractions and compounds showed pronounced antioxidant activities in all of the different antioxidant assays.
• Some phenolics showed neuroprotective effect against H2O2-induced oxidative stress in SH-SY5Y cell.

Chinese hickory (Carya cathayensis Sarg.) is a common and nutritious nut. Twenty-nine phenolic compounds, together with three quinones and three triterpenoids, were isolated from Chinese hickory husks. Their structures were determined by comprehensive spectroscopic methods. The total methanolic extract, chloroform and ethyl acetate fractions and all the isolated compounds were evaluated for antioxidant activity and neuroprotective effects on SH-SY5Y cells, as well as the effects on the expression of PPAR-γ in 3T3-L1 cells. Quercetin (10) and protocatechuic acid methyl ester (24) showed pronounced antioxidant activities in all of the different antioxidant assays and neuroprotective effect against H2O2-induced oxidative stress. Some of the flavonoids could significantly decrease the mRNA expression level of PPAR-γ by approximately 70%. The present study provided supplement information for the evaluation of antioxidant activity and health benefit of Chinese hickory.