Determination of Polyphenol, Antioxidant Activity, and Individual Phenolic Compounds in Tubers of Sweet Potato Varieties Grown in South Carolina

The effect of varieties of sweet potato (Purple, Burgundy, Beaureguard and Porto Rico) grown in South Carolina on the antioxidant activity, polyphenol content, and individual phenolic compounds were tested. The sweet potato tuber shapes being studied consisted of an irregular, oval and elliptical while flesh color was purple for Purple, orange for Burgundy and Beaureguard, and light yellow for Porto Rico. The dry matter (DM) content was 30-37%. The Porto Rico cultivar showed the lowest polyphenol content of 57.5 mg gallic acid equivalent (GAE)/100g DM, and antioxidant activity 37.2 mg Trolox equivalent (TE)/100g DM. The highest polyphenol content, 382.7 mg GAE/100g DM and antioxidant activity 222.2 mg TE/100g of DM were found in purple cultivar. High performance liquid chromatography data showed the gallic acid, catechin, chlorogenic acid, caffeic acid, p-coumaric acid, ferulic acid, m-coumaric acid, rosmarinic acid in tubers, and the predominant ones were chlorogenic acids 11.4 mg/g of DM in Purple cultivar.