Antioxidant activity, nitric oxide scavenging activity and phenolic contents of Ocimum gratissimum leaf extract

Plant derived antioxidant could be useful as food additives to prevent food deterioration and also to impart human health and prevent oxidative stress associated diseases. In this study, the free radical scavenging potential of a methanol extract of the leaves of Ocimum gratissimum was assessed by measuring its capability for scavenging 2,2-diphenyl-1-picrylhydrazyl (DPPH.) radical, superoxide anion radical (O2.–), hydroxyl  radical (.OH), nitric oxide radicals (NO.), as well as its ability to inhibit lipid peroxidation, using appropriate assay systems compared to natural and synthetic antioxidants. Total phenolic, flavonoid and flavonol contents were determined by spectrophotometric methods. The extract significantly inhibited DPPH radical with an IC50 value of 12.3± 1.95µg/ml, inhibited O2.– (IC50 = 82.9 ± 5.12 µg/ml), .OH radical (IC50 = 38.9 ± 2.8µg/ml) and non-enzymatic lipid peroxidation (IC50 = 270.5 ± 8.2 µg/ml) and also inhibited the accumulation of nitrite in vitro. The plant extract yielded 0.839 ± 0.097mg gallic acid equivalents phenolic content and 39.12 ± 2.43 mg rutin equivalents flavonoid content. The observed antioxidant potentials and phenolic content of the extract suggest that an ethanol extract of O. gratissimum leaves is a potential source of natural antioxidants and could be useful in the food industry to retard oxidative degradation of lipids and thereby improve food quality. However, isolating the active principles and in vivo studies are warranted.   Key words: Ocimum gratissimum extract, antioxidant activity, NO. scavenging activity, phenolic content.