Comparative antioxidant studies of methanol pericarp, mesocarp, seed and whole-fruit extracts and fractions of Citrullus lanatus

Abstract

Aim: This study evaluated the antioxidant potentials of methanol seed, pericarp, mesocarp, and whole-fruit extracts and fractions of Citrillus lanatus. Methods: Various extracts and fractions (dichloromethane, ethyl acetate, n-butanol and aqueous) of Citrillus lanatus whole-fruit were investigated for 1, 1-diphenyl-2-picrylhydrazyl (DPPH) scavenging activities, total phenolic content (TPC) and ferric reducing antioxidant power (FRAP). Results: In the DPPH assay, the seed extract showed the highest activity (48%) followed by the whole-fruit extract (27%), pericarp (26%) and the mesocarp (22%) at 100 ug/ml. The whole-fruit fractions also showed improved activity with DCM fraction (64%), ethyl acetate (62%), aqueous fraction (46%) and n-butanol (24%) at 100 ug/ml but the activity observed with ascorbic acid, was much higher (84%). The seed extract had the highest phenolic content (14.30 mg) gallic acid equivalents per gram followed by the pericarp (9.58 mg/g), whole-fruit (6.94 mg/g) and mesocarp (2.78 mg/g). The DCM fraction exhibited the highest TPC (78.19 mg/g) followed by ethyl acetate (61.11 mg/g), aqueous (26.66 mg/g) and n-butanol (10.69 mg/g). FRAP assay showed strongest activity with the whole-fruit extract (0.640nm) followed by seed, mesocarp and pericarp extracts. The DCM fraction showed the highest antioxidant potential (0.735nm) followed by ethyl acetate, aqueous and n-butanol fractions but not comparable to ascorbic acid. Conclusion: The results revealed that C. lanatus seeds, pericarp, mesocarp and whole-fruit extracts and fractions contain varying amounts of flavonoids, tannins and phenolic compounds which exhibit potent antioxidant and free radical scavenging activities.