Effect of Extraction Procedures, Genotypes and Screening Methods to Measure the Antioxidant Potential and Phenolic Content of Orange-fleshed Sweetpotatoes ( Ipomoea batatas L.)

摘要

The antioxidant activities and phenolic contents of the five orange-fleshed sweetpotato genotypes namely SP-122, SP-129, SP-115, SP-323 and SP-425 in relation to the two extraction methods (hydrophilic and lipophilic fraction) were examined. The antioxidant capacity was investigated with three different screening methods: the 2, 2?-azinobis (3-ethyl-benzothiazoline-6-sulfonic acid) (ABTS), 2, 2-diphenyl-1-picrylhydrazyl (DPPH) and Oxygen Radical Absorbance Capacity (ORAC). It was found that the antioxidant activity of sweetpotato extracts in hydrophilic fraction have a significant antioxidant effect when tested by each method. There was a relationship between total polyphenol content and antioxidant function in case of ABTS (r = 0.59) and ORAC (r = 0.35). The hydrophilic ABTS values correlate significantly with the hydrophilic DPPH values (r = 0.84) and the hydrophilic ORAC values correlate reasonably well with the hydrophilic ABTS values (r = 0.85). In case of the hydrophilic DPPH values and hydrophilic ORAC values also showed a strong correlation (r = 0.87). However, antioxidant activities with the lipophilic extracts were not significantly correlated. Among the sweetpotato genotypes studied, the SP-129 had significantly higher antioxidant activity in ORAC and ABTS methods. In case of DPPH methods, the genotypes SP-425 showed higher activity compared to others studied; however, phenolic content of all genotypes was ranged 3.5-4.8 mg TAE/g dry weight. Among the methods examined, ABTS proved the best for antioxidant determination in orange-fleshed sweetpotatoes followed by ORAC method. The information provided by this research will also facilitate the genetic and chemical breeding study for improvement of the desired quality criteria of orange fleshed sweetpotatoes as well as other produces.