Evaluation of the Antioxidant Properties of Some Commonly Eaten Vegetables in Akwa Ibom State of Nigeria

Aims: To evaluate the antioxidant components and also antioxidant activities of ten local vegetables commonly consumed in Akwa Ibom State, Nigeria.
Place and Duration of Study: Department of Pharmaceutical and Medicinal Chemistry, Faculty of Pharmacy, University of Uyo, Akwa Ibom State, Nigeria between April 2011 and July 2012.
Methodology: Standard methods were used to evaluate the concentration of total phenols, vitamin C, vitamin E, total flavonoids, total tannins, anthocyanin, β-carotene and lycopene in the leaves of Heinsia crinata, Ocimum gratissimum, Telfaira occidentalis, Talinum triangulare, Corchorus olitorius, Amaranthus hybridus, Gnetum africana, Vernonia amygdalina, Gongronema latifolia and Lasianthera africana. Ferric reducing antioxidant power (FRAP), iron chelating activity, Nitric oxide and 2,2-Diphenyl-1-Picrylhydrazyl (DPPH)-radical scavenging activities, and total antioxidant activity were also determined using standard methods.
Results: Lasianthera africana recorded the highest amount of Lycopene (0.9951±2.23×10-3.mg/100ml) and Anthocyanin (0.0943±1.30×10-3). Gongronema latifolium also recorded the highest amount of Tannin (6.6±1.01×10-3 mg/100g) and β-carotene (1.692±1.31×10-4 mg/100 ml). Similarly, Hensia crinata, Cochorius olitorius and Vernonia amygdalina recorded the highest amount of Vitamin E (24.761±7.22×10-2 µM), total phenol (0.100±6.84×10-5 mg/ml) and flavonoids (36.784±1.72×10-2 mg/ml), respectively. Ocimum gratissimum gave the highest % inhibition (74.0%) of DPPH at a concentration of 60 µg/ml of extracts compared to the standard drugs (Vitamin C, 92.0% and Vitamin E, 35.0%). Vernonia amygdalina showed highest inhibition (89.97%) of Nitric Oxide while Ocimum gratissimum inhibited ferric reducing antioxidant activity by 91.43%. It was found that Vitamin C correlated significantly with the antioxidant activity (r2=0.7072, P=0.05). Flavonoids also correlated significantly with the Ferric Reducing antioxidant Power (r2=0.6784, P<0.05).
Conclusion: Ocimum gratissimum exhibited the best antioxidant activity and should be explored further for this purpose.