Comparative study on chemical composition, polyphenols, flavonoids, carotenoids and antioxidant activities of various cultivars of sweet potato

Chemical composition, polyphenols, flavonoids, carotenoids and antioxidant activities of twenty-five cultivars of sweet potato were investigated. Starch, crude protein, crude fat, total dietary fibre, reducing sugar and ash contents ranged between 51.88-69.21, 2.36-7.79, 0.24-1.11, 5.02-14.35, 1.07-9.78 and 1.95-4.29 g per 100 g dry weight (DW), respectively. Cultivars of Longshu, Pushu 32 and Qinshu No.7 (Shanxi province) displayed the highest values in total polyphenol contents (9.38, 9.11 and 8.76 mg GAE per g DW, respectively), Huangmeigui showed higher flavonoids content (2.54 mg RE per g DW), Xiangshu presented higher anthocyanin content (1.02 mg per g DW), whereas Pushu 32 had the highest beta-carotene content (208.11 mu g per g DW). Strong significant positive correlations were presented between antioxidant activities and total polyphenol and flavonoid contents, indicating that polyphenols and flavonoids are essential antioxidants in sweet potatoes. Among all cultivars, Pushu 32 presented the highest grey relational grade (GRG) value (0.7811), suggesting its importance as a healthy diet.