Effects of Treatment Methods on Total Polyphenol Content and Antioxidant Activity of Polygonum Multiflorum Thunb Root Extract

Abstract

The study shows the changes of total polyphenol compounds and antioxidant activities of Polygonum multiflorum Thunb root extract during the preservation time by freezing method. In addition, the treatment of initially raw materials by drying process also affects strongly total polyphenol compounds and antioxidant activity. Total phenolic compounds were determined by the Folin Ciocalteu method and antioxidant activity was analyzed by radical scavenging activity on 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical. The results point out that Polygonum multiflorum Thunb (fresh samples) can be preserved for 3 months at -20oC but content of polyphenol and antioxidant activity decrease significantly by 60%. Fresh samples were dried at 60oC for 4 hours and methods including magnetic stirrer extraction (MSE), microwave-assisted extraction (MAE), ultrasound-assisted extraction (UAE), and enzyme (Termamyl SC) assisted extraction (EAE) with deionized water as solvent, were used to extract polyphenol in this research. MAE has the shortest treatment time (6 minutes) and the best results (highest total polyphenol) as 44.37 mg GAE/g DW and antioxidant activity value was 132.73 μmol Trolox/g DW. Conversely, EAE and MSE methods give the worst yield (22.81 mg GAE/g DW, 24.51 mg GAE/g DW and 136 μmol Trolox/g DW, 175.29 μmol Trolox/g DW respectively) and require the longest extraction time (from 1 to 2 hours).