Screening and isolation of natural antioxidants from Acer ginnala Max. by TLC-MS/MS guided bioautographic method

A rapid and simple method has been developed for the screening and identification of natural antioxidants from the leaves of Acer ginnala Maxim.( AG). The process is that upon reaction with 1,1-diphenyl-2-picrylhydrazyl (DPPH), the white yellow spots of compounds with potential antioxidant effects will be significantly observed on the thin-layer chromatography (TLC), and possible structures will be presumed by the ESI/MS technique. Using the improved approach, 6 compounds in the AG extract were found to possess a potential antioxidant activity. They were speculated as quercetin-3-O-α-L-(3''-galloyl)-rhamnoside (1), quercetin-3-O-α-L-(2''-galloyl)-rhamnoside (2), quercetin-3-O-α-L-(2''-galloyl)-arabinopyranoside (3), acertannin (4), gallic acid (5) and methyl gallate (6). In addition, we were still found that compounds 2, 3 and 5 had favorable antioxidant activity from the scannogram of the DPPH reaction plate. As a result, the isolated 6 compounds structures were in accord with the presumed structures. Furthermore, the free radical scavenging capacities of the available identified compounds were also investigated. Compounds 2, 3 and 5 showed significant DPPH. scavenging capacities, with IC50 values of 2.83 μg/mL, 2.34 μg/mL, 1.86μg/mL, respectively. The results indicated that this newly improved method could be widely applied for rapid screening and identification of natural antioxidants from Chinese herbal medicines.