The antioxidant and phenolic profiles of five green vegetables grown in Southern Nigeria.

BACKGROUND

Regular consumption of vegetables has been associated with reduced risk of chronic diseases. The phenolic and free radical scavenging properties of five green vegetables grown in southern Nigeria were determined.

METHODS

The phenolic and antioxidant profile of African spinach, bitter leaf, jute leaf, scent leaf and water leaf harvested in the month of August were assessed using standard protocols.

RESULTS

The total phenolic content (GAE mg/100 g) of the fresh vegetables ranges from 738.70 ±7.90 in African spinach to 1464.63 ±7.60 in scent leaf. A higher flavonoid content (QE mg/100 g) was found in water leaf (512.07 ±1.47) and jute leaf (510.13 ±2.22) compared to the other vegetables examined; scent leaf (496.51 ±1.31), African spinach (457.40 ±1.50), bitter leaf (371.89 ±0.44). Scent leaf possesses the highest DPPH radical scavenging activity with an EC50 [μg/mL] of 74.64 ±7.73. The other vegetables show a lower EC50 [μg/mL]; jute leaf (125.86 ±11.34) > water leaf (132.43 ±9.43) > bitter leaf (156.02 ±5.43) > African spinach (213.44 ±9.29). The hydroxyl radical scavenging activity (EC50, μg/mL) of the vegetables in order of decreasing activity, was bitter leaf (50.38 ±7.17) > water leaf (103.41 ±6.27) > African spinach   (110.54±8.15) > jute leaf (144.39 ±9.37) > scent leaf (217.51 ±6.90). The total antioxidant capacity (EC50, μg/mL) of the vegetables increases in the following order; African spinach (227.39 ±7.25) < bitter leaf (169.96±6.86) < water leaf (106.31 ±7.66) < scent leaf (65.47 ±14.43) < jute leaf (27.52  ±4.14).

CONCLUSIONS

The green vegetables possess appreciable phenolic and antioxidant potentials, which underscore their regular consumption as part of healthy Nigerian diet. Principal component analysis (PCA) buttresses the correlations and variations of the aforementioned potential among vegetable species.