Determination of phenolic content and its effect on antioxidant activity in selected edible plants / Noor Adillah Abdullah

The main objectives of this final year project are to determine the total phenolic content and antioxidant acticity in 6 selected edible plants and also to evaluate the relationship between total phenolic content and antioxidant activity in the plants. six edible plants namely kesum leaves, pucuk manis, mint, ulam raja, selom leaves and tapioca shoot were selected for this study. The total phenolic content in the plants were determined by using drying method and direct spectrophotometric absorption at 750nm against a standard calibration curve with gallic acid as standard. The amount of total phenolic content determined by using the drying method were 9.72%, 7.66%, 6.34%, 5.25%, 3.31% and 0.57% in kesum leaves, selom leaves, tapioca shoots, mint, ulam raja and pucuk manis, respectively. Kesum leaves, selom leaves, tapioca shoots, ulam raja, pucuk manis and mint contained 109.96mg, 65.58mg, 36.54mg, 32.06mg, 26.07mg and 12.71mg of total phenolic content per lOOg of the plants determined by using the spectrophotometer method.The percentage of antioxidant activity in the plants was expressed as the percentage of inhibition relative to the control. The measurement of antioxidant activity by the p-carotene bleaching method showed that the antioxidant activity in the samples were 42.24%, 25.64%, 20.51%, 12.82% 12.70%, and 8.06% respectively, which were significantly lower than those of the standards tocopherol 50 ppm (71.79%) and BHT 50 ppm (53.48%). The correlation coefficient value obtained for total phenolic content determined by using drying method and the antioxidant activity was r2 = 0.6273, while the correlation coefficient value obtained for total phenolic content determined by using spectrophotometer method and the antioxidant activity was i2 = 0.5172.