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

Abstract

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.