Evaluation of bioactive compound content, in-vitro antioxidant and anti-inflammatory effects of ethanol extract of the seed of Cucumis metuliferus fruit

Cucumis metuliferus commonly called Kiwano is a well-known plant in the middle belt area of Nigeria. It is consumed for nutritional and medicinal purposes. This study evaluated the bioactive compound content, In-vitro antioxidant and anti-inflammatory properties of ethanol extract of the seed of Cucumis metuliferus fruit. The antioxidant properties were evaluated using DPPH (2, 2 diphenyl-1-picrylhydrazyl) radical, iron reducing power and inhibition of lipid peroxidation tests. Ascorbic acid served as standard. The anti-inflammatory activity at concentration of 200-1000 µg/ml was measured In-vitro using anti-proteinase activity, membrane stabilization and inhibition of albumin denaturation assay systems. Aspirin and diclofenac were used as reference drugs. The bioactive compounds evaluated were phenol, flavonoid, beta carotene, lycopene and ascorbic acid. From the result, the seed extract contains phenol (149.40±9.93 mgGAE/g), flavonoids (97.84±2.84 mgCE/g), beta carotene (0.110±0.001 mg/g), lycopene (0.085±0.001 mg/g) and ascorbic acid (0.190±0.028 mgAA/g). In the antioxidant assays, the antioxidant activities were dependent on the concentration. At lower concentrations, the seed extract displayed higher activity in all the assays compared with the standard. The DPPH scavenging and lipid inhibition abilities of the seed were more potent with lower IC50 while the reductive potential of the standard was better. From the anti-inflammatory assays, the seed extract exhibited anti-proteinase activity of 0-8.78%, membrane stabilization (inhibition of heat-induced haemolysis) activity of 5.13-20.51% and percent inhibition of albumin denaturation of 0.78-16.15%. These results showed that ethanol extract of Cucumis metuliferus seed contains bioactive compounds which are beneficial to health and possess antioxidant and anti-inflammatory abilities.