Screening of Key Antioxidant Compounds of Longan (Dimocarpus longan Lour.) Seed Extract by Combining Online Fishing/Knockout, Activity Evaluation, Fourier Transform Ion Cyclotron Resonance Mass Spectrometry, and High-Performance Liquid Chromatography Electrospray Ionization Mass Spectrometry Methods

摘要

To figure out the key phenolic compounds accounting for the antioxidant effects of longan (Dimocarpus longan Lour.) seed extract, online fishing/knockout method, activity evaluation assays, Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR—MS), and high-performance liquid chromatography electrospray ionization mass spectrometry (HPLC— ESI—MS) analysis were used jointly for the first time. p-Coumaric acid—glycoside, (S)-flavogallonic acid, ellagic add derivative, and methyl-ellagic acid glucopyranoside were first identified in longan seeds. In addition, our study revealed that ellagic acid as well as its derivative and p-coumaric acid—glycoside had important contribution to the potent antioxidant activity of longan seed extract, while gallic acid, corilagin, (S)-flavogallonic acid, methyl-ellagic acid glucopyranoside, and ethyl gallate showed very little contribution to the total antioxidant activity of longan seed extract. The combining use of the online fishing/knockout method, activity evaluation assays, FT-ICR—MS, and HPLC—ESI—MS analysis is a useful and simple strategy for screening Of key bioactive compounds from complex extracts.