Evaluation of Anti-inflammatory and Antioxidant Effects of Ethanol Extract of Dissotis Rotundifolia Leaves

Abstract

This study investigated the anti-inflammatory and antioxidant effects of the ethanol extract of Dissotis rotundifolia leaves. This study utilized maceration with ethanol as the extraction method. The phytoconstituents, antioxidant vitamin content as well as acute toxicity of the plant leaf extract were all determined. The anti-inflammatory activity of the ethanol extract was evaluated by determining its inhibitory effect on egg albumin-induced rat paw oedema, phospholipase A2 activity, calcium chloride-induced platelet aggregatory response, hypotonicity-induced hemolysis of red blood cells, protease inhibition and albumin denaturation. The extract was also investigated for its antioxidant action against free radicals using diverse methods including; lipid peroxidation, 2,2-diphenyl-1-picryl hydrazyl (DPPH) radical scavenging activity, nitric oxide radical and Ferric Reducing Antioxidant Power (FRAP) assays. Linear regression analysis was used to calculate the IC50 value. The percentage yield of the leaves was 3.76 % w/w. Phytochemical analyses of the extract revealed the presence of phenols (1774.19 ± 32.26 mg/100 g), tannins (836.54 ± 12.82 mg/100 g) and terpenoids (236.98 ± 3.60 mg/100 g), (1.17 ± 0.21 mg/100 g), glycosides (22.29 ± 22.29 mg/100 g (0.39 ± 0.02 mg/100 g) and alkaloids (12.37 ± 0.72 mg/100 g). The antioxidant vitamin composition showed trace amounts of the antioxidant vitamins; A, C and E in the leaf extract. The acute toxicity test of the extract showed no toxicity up to 5000 mg/kg body weight. The egg albumin-induced rat paw oedema study showed that at 100, 200 and 400 mg/kg body weight, the extract exhibited a significant (p < 0.05) reduction in the rat paw volume from within 5 hours when compared to the control. The extract also significantly inhibited phospholipase A2 activity in a concentration-dependent manner when compared to the control, with a range of 0.2 to 1.0 mg/ml inhibiting the enzyme activity by 47 % to 61 %. The extract also significantly (p < 0.05) inhibited, calcium chloride induced platelet aggregation, hypotonicity-induced hemolysis of red blood cells, protease inhibition and albumin denaturation in a concentration-dependent manner. The ethanol extract of D. rotundifolia leaves was able to significantly (p < 0.05) inhibit the initiation or propagation of oxidative chain reactions by effectively inhibiting lipid peroxidation, DPPH radical, NO radical and also, by reducing ferric ions to ferrous ions in the FRAP assay. The inhibitory effect of the extract on free radicals may partially explain why the extract is beneficial in ameliorating inflammatory conditions. The diverse mechanisms of action of the different concentrations of the ethanol extract of D. rotundifolia leaves could be due to the presence of some of the identified constituents present in the leaf extract. The investigation therefore, shows that D. rotundifolia leaf extract, used in folkloric treatment of inflammatory disorders, has anti-inflammatory and antioxidant properties