In Vitro Antioxidant Activity and Nitric Oxide Scavenging Activity of Citrullus Lanatus Seeds.

Citrullus lanatus (water melon) is a commonly consumed fruit worldwide .The seeds are often thrown away without considering its potential nutritional and medicinal benefits. In this study, a methanol extract of citrullus lanatus seeds was analyzed for the presence of bioactive secondary metabolites and to determine its ability to scavenge 2, 2? diphenyl ?1? picrylhydrazyl (DPPH.) radical, superoxide anion radical (O2.?), and nitric oxide radical (NO.). Quantitative phytochemical analysis was done spectrophotometrically using standard methods. The result showed that the total phenol concentration was 0.96 ± 0.12 mg RE and flavonoid was 9.96 ± 0.86 mg GAE. The extract showed a potent DPPH radical scavenging activity by changing the extract spots from purple to yellow on the thin layer chromatographic (TLC) plate. At the concentration of 1000 µg/ml the extract had its maximum inhibition of 93.85 ± 4.73 % compared to that of ascorbate (95.70 ± 1.71 %).The extract also had a good O2- anion radical scavenging ability with IC50 = 44.65 ± 3.21 µg/mL compared to rutin (IC50 = 12.01 ± 2.59 ?g/mL). In the 5 mM sodium nitroprusside (SNP) only medium the levels of nitrite and hence nitric oxide (NO.) was significantly higher (p<0.05) at every time interval compared to the observed levels in the presence of the citrullus lanatus seed extract. This therefore suggests that the citrullus lanatus seed could be a good source of antioxidants to ameliorate conditions in diseases whose pathogenesis implicates oxidative stress. Keywords; Citrullus lanatus, oxidative stress, antioxidants,Scavenging activity,Metabolites