Contribution of .BETA.-Carotene to Radical Scavenging Capacity Varies among Orange-fleshed Sweet Potato Cultivars

Abstract

Orange-fleshed sweet potato (OR-SP) cultivars rich in β-carotene are considered to exhibit higher antioxidant capacity than yellow-fleshed sweet potato (YE-SP) cultivars, consumed commonly in Japan. However, little information exists on the contribution of β-carotene to the antioxidant property. In this study, 2,2′-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) cation radical (ABTS•+) scavenging capacity in eight OR-SP cultivars and three YE-SP cultivars were measured and compared. The radical scavenging capacity of OR-SP ranged from 493 to 969μmol Trolox equivalent (TE)/kg fresh weight (FW), and that of YE-SP ranged from 254 to 728μmol TE/kg FW. The β-carotene content in OR-SP ranged from 139 to 330μmol/kg FW and it exhibited 1.66 times higher radical scavenging capacity than a Trolox standard. The contribution of β-carotene to the total radical scavenging capacity was estimated to be in a range of 36.3 to 79.6% in OR-SP. Moreover, by staining the TLC plate with an ABTS•+ solution after separating the constituents, it was suggested that a species of radical scavengers were common to all cultivars.