Liquid Chromatography-Tandem Mass Spectrometry Screening Method for the Detection of Radical-Scavenging Natural Antioxidants from the Whole Scutellariae (Radix, Stem and Leaf).

A novel free radical reaction combined with high-performance LC-photodiode array-ESI-MS/MS screening method was developed for the detection and identification of natural antioxidants from whole Scutellariae. Six compounds and whole Scutellariae extracts were found to possess a potential antioxidant capacity, and their free radical-scavenging activities were investigated in detail. The six compounds were identified as baicalin, baicalein, scutellarin, scutellarein, wogonoside and chrystin-7-glucoronide. The present study reveals that the radical-scavenging capacities of the whole Scutellariae extracts are as follows: hydroxyl radical > superoxide radical > peroxy radical. Wogonoside showed the strongest capability for scavenging hydroxyl radical. Baicalein not only showed the strongest capability for scavenging superoxide radical but also showed capability for lipid radical; Scutellarein (Peak 5) exhibited the highest reactivity in the lipid peroxidation processes. Based on these studies, the current paper accomplishes the evaluation of activities of some important anti-radical substances extracted from the radix, stem and leaf of the whole Scutellariae.

Functionalized graphene quantum dots loaded with free radicals combined with liquid chromatography and tandem mass spectrometry to screen radical scavenging natural antioxidants from Licorice and Scutellariae.

A novel screening method was developed for the detection and identification of radical scavenging natural antioxidants based on a free radical reaction combined with liquid chromatography with tandem mass spectrometry. Functionalized graphene quantum dots were prepared for loading free radicals in the complex screening system. The detection was performed with and without a preliminary exposure of the samples to specific free radicals on the functionalized graphene quantum dots, which can facilitate charge transfer between free radicals and antioxidants. The difference in chromatographic peak areas was used to identify potential antioxidants. This is a novel approach to simultaneously evaluate the antioxidant power of a component versus a free radical, and to identify it in a vegetal matrix. The structures of the antioxidants in the samples were identified using tandem mass spectrometry and comparison with standards. Fourteen compounds were found to possess potential antioxidant activity, and their free radical scavenging capacities were investigated. The order of scavenging capacity of 14 compounds was compared according to their free radical scavenging rate. 4',5,6,7-Tetrahydroxyflavone (radical scavenging rate: 0.05253 mL mg(-1) s(-1) ) showed the strongest capability for scavenging free radicals.

Loading of free radicals on the functional graphene combined with liquid chromatography-tandem mass spectrometry screening method for the detection of radical-scavenging natural antioxidants.

A novel free radical reaction combined with liquid chromatography electrospray ionization tandem mass spectrometry (FRR-LC-PDA-ESI/APCI-MS/MS) screening method was developed for the detection and identification of radical-scavenging natural antioxidants. Functionalized graphene was prepared by chemical method for loading free radicals (superoxide radical, peroxyl radical and PAHs free radical). Separation was performed with and without a preliminary exposure of the sample to specific free radicals on the functionalized graphene, which can facilitate reaction kinetics (charge transfers) between free radicals and potential antioxidants. The difference in chromatographic peak areas is used to identify potential antioxidants. The structure of the antioxidants in one sample (Swertia chirayita) is identified using MS/MS and comparison with standards. Thirteen compounds were found to possess potential antioxidant activity, and their free radical-scavenging capacities were investigated. The thirteen compounds were identified as 1,3,5-trihydroxyxanthone-8-O-ß-D-glucopyranoside (PD1), norswertianin (PD2), 1,3,5,8-tetrahydroxyxanthone (PD3), 3, 3', 4', 5, 8-penta hydroxyflavone-6-ß-D-glucopyranosiduronic acid-6'-pentopyranose-7-O-glucopyranoside (PD4), 1,5,8-trihydroxy-3-methoxyxanthone (PD5), swertiamarin (PS1), 2-C-ß-D-glucopyranosyl-1,3,7-trihydroxylxanthone (PS2), 1,3,7-trihydroxylxanthone-8-O-ß-D-glucopyranoside (PL1), 1,3,8-trihydroxyl xanthone-5-O-ß-D-glucopyranoside (PL2), 1,3,7-trihydroxy-8-methoxyxanthone (PL3), 1,2,3-trihydroxy-7,8-dimethoxyxanthone (PL4), 1,8-dihydroxy-2,6-dimethoxy xanthone (PL5) and 1,3,5,8-tetramethoxydecussatin (PL6). The reactivity and SC50 values of those compounds were investigated, respectively. PD4 showed the strongest capability for scavenging PAHs free radical; PL4 showed prominent scavenging capacities in the lipid peroxidation processes; it was found that all components in S. chirayita exhibited weak reactivity in the superoxide radical scavenging capacity. The use of the free radical reaction screening method based on LC-PDA-ESI/APCI-MS/MS would provide a new approach for rapid detection and identification of radical-scavenging natural antioxidants from complex matrices.