Compounds 2-6 showed the TEAC values close or over 1.0, relative to a vitamin E analog Trolox, suggesting that their radical scavenging ability is similar or greater than that of Trolox. As anticipated from the calculated E° values, relatively low TEAC values were observed for 2 and 3 over 4 and 6. This investigation manifests the significance of the number of hydroxyl groups on the A ring towards redox properties and antioxidant activity. Despite three hydroxyl groups on the A ring, 5 with an electron-withdrawing chloro group displayed a similar TEAC value with 2 and 3 containing two hydroxyl groups. Our computational and experimental studies confirm that the flavonoid (6) embodying three hydroxyl groups without an electron-withdrawing substituent on the A ring can has the lowest redox potential among 1-6, with the consequent noticeable radical scavenging ability.