Effect of Heat on Antioxidant Activity of Some Tropical Leafy Vegetables

The present study examined the effect of different cooking times on total phenolics, total flavonoids, ascorbic acid content and antioxidant properties of seven tropical leafy vegetables: Pterocarpus mildbraedii, Gongronema latifolium, Ocimum gratissimum, Solanecio biafrae, Piper guineense, Celosia argentea and Solanum melongena. The thermal treatments employed were both long simmer (20 minutes at 80oC) and short simmer (5 minutes at 80oC). The result show that both short and long simmer results to a significant decrease (P< 0.05) in the ascorbic acid content in all the vegetables. There was a significant increase in the total phenol, total flavonoid, DPPH radical scavenging ability, reducing property, Fe2+ chelating ability and hydroxyl radical scavenging ability. In like manner, short simmer treatment enhances the total antioxidant activities of all the vegetables. These results suggest that although thermal treatments enhances the nutritional value of vegetables by increasing the bio-accessible phenolic content and total antioxidant activity, long simmer treatment results in the disruption of the phytochemicals constituents present. The study therefore concludes that short time simmer treatment may result to optimum yield of antioxidant activities in leafy vegetables.Keywords: Antioxidant activity, Ascorbic acid, Leafy vegetables, Total flavonoids, Total phenolic

Preliminary evaluation of some aspects of the ecology (growth pattern, condition factor and reproductive biology) of African pike, Hepsetus odoe (Bloch 1794), in Lake Eleiyele, Ibadan, Nigeria

Abstract A preliminary investigation of length-weight relationship, condition factor and reproductive ecology of African pike fish, Hepsetus odoe, was conducted between June to August 2010 in Lake Eleiyele. A total of 90 samples of the fish species were caught by fishermen using gill nets. The results obtained showed that fish species had isometric growth pattern (contrary to negative allometry expected) with the growth exponent, b value of 2.64, that is not statistically different from 3 and with high statistical power of 0.866 when tested. The mean condition factor, K, was found to be 2.6, indicating that the fish species were in good condition in the study area. For reproductive biology, mean fecundity and gonadosomatic index were found to be 1349 eggs and 3.53% respectively. This study was necessary to fill the knowledge gap and provide information for management and conservation of the investigated species in the lake system. This study recommended that further research needs to be conducted because the sampling was carried out in the rainy season period and within a quarter of a year