Antioxidant, metabolic enzymes inhibitory ability of Torreya grandis kernels, and phytochemical profiling identified by HPLC-QTOF-MS/MS.

Abstract

In this study, the antioxidant activities, α-glucosidase and tyrosinase inhibitory ability of Torreya grandis kernels (TGK) were performed. Samples were extracted with various polarity of ethanol, and the major phytochemical profile was characterized. The results showed that 70% of ethanol extract gave the richest phenolics and flavonoids. The strongest DPPH· and ABTS·+ scavenging ability, as well as the best inhibition on tyrosinase and α-glucosidase was also detected on 70% of ethanol extract. Among the fractions of 70% of ethanol extract, the ethyl acetate fraction (EAF) owned the highest phenolics, flavonoids, and the best DPPH· and ABTS·+ scavenging ability, and tyrosinase inhibition. Unexpectedly, the dichloromethane fraction possessed the strongest inhibition on α-glucosidase, which was much greater than that of acarbose. HPLC-QTOF-MS/MS analysis result to the characterization of 19 compounds from EAF. The results implied that TGK can be a potential source of natural antioxidants, α-glucosidase and tyrosinase inhibitors. Practical applications The kernels of T. grandis are one of the precious nuts in the world, and the extracts were advertised to show a variety of biological activities and pharmacological effects. However, researches on the phytochemical constituents and bioactivities are fewer. In this study, TGK was found to show good potency in antioxidant, α-glucosidase and tyrosinase inhibitory activities. The 70% ethanol is the best solvent for extracting above mentioned active components, and ethyl acetate can be the suitable enriching solvent. In addition, the predominant phytochemical compounds in EAF were characterized. Therefore, this research can help to the performance of further research and application of TGK in functional products.