3.3. Antioxidant activity
The antioxidant activity was determined by using DPPH method, one of the most effective methods for evaluating radical-scavengers [12].
The scavenging activity of the methanolic extracts of peel powder and peel jelly and IC50 value were showed in Table 3 and Table 4 respectively. At the concentration of 0.1 mg/mL, the peel powder with IC50 value of 1.56 mg/mL showed 20% scavenging activity, while at the highest concentration of 10 mg/mL, it showed the greatest scavenging activity reached at 89%. The 5%–7% peel jelly showed IC50 values from 3.11 to 3.95 mg/mL, and the scavenging activity at the lowest concentration ranged from 7% to 11%. Otherwise, the 5%–7% peel jelly at 10 mg/mL increased scavenging activity from 74% to 84%. That remarkable scavenging activity was quite high as compared with commercial jelly with IC50 of 4.28 mg/mL and scavenging activity of 36% which was almost half of scavenging activity of 7% peel jelly. In addition, at the same concentrations, the scavenging activities of 5% and 6% peel jelly were also slightly higher than that of commercial jelly.