Anti-hyperglycaemic, anti-inflammatory and anti-oxidant activities of <i>Carica papaya</i> and <i>Citrullus lanatus</i> seeds

Abstract

The study investigated the anti-hyperglycaemic, anti-inflammatory and antioxidant potentials of methanolic seed extracts of Carica papaya and Citrillus lantus. The inhibitory effects of the extracts (100, 200 and 400 mg/kg, orally) on a-amylase and a-glucosidase were assessed in glucose and sucrose-induced hyperglycaemic rats using glimepiride (25 mg/kg) and acarbose (50 mg/kg), as positive controls. The anti-inflammatory activities were evaluated by  membrane stability, xanthine oxidase inhibition and inhibition of denaturation of albumin models. Their antioxidant potentials were determined using standard methods and their total phenolic and flavonoid contents were also estimated. The extracts gave a comparable (p>0.05) hyperglycaemia lowering and a-glucosidase inhibitory activities to glimepiride (25 mg/kg) and acarbose (50 mg/kg), respectively. However, C. papaya gave a significantly (p<0.05) higher a-amylase inhibitory activity than C. lanatus at all concentrations. The seed extract of C. papaya was significantly more active in red blood cell membrane stabilizing activity at all concentrations than C. lanatus and ibuprofen while their order of xanthine oxidase inhibitory activities was: allopurinol > C. papaya > C. lanatus. In albumin denaturation assay, C. papaya gave a comparable activity to the positive control at 0.25 – 1.00 μg/ml and significantly higher effect at 0.0625-0.125 μg/ml while in the 1, 1, diphenyl-2-picrylhydrazyl (DPPH) radical scavenging, total antioxidant capacity (TAC) and ferric reducing antioxidant power (FRAP) assays, the order of antioxidant activities was, ascorbic acid (positive control) > C. papaya > C. lanatus. The total phenolic and flavonoid contents of C. papaya expressed as gallic acid and quercetin equivalents were found to be 82.00 and 35.00 mg/g respectively; while those of C. lanatus were 40.00 and 20.00 mg/g, respectively. The results showed the seed extract of C. papaya to be a better anti-hyperglycaemic, antiinflammatory and antioxidant agent than C. lanatus and suggested that their high flavonoid and phenolic contents could be responsible for these activities.

Keywords: Hyperglycaemia lowering, Antioxidant, Anti-inflammatory, C. papaya, C. lanatus seeds