Prophylactic Efficacy of Moringa Oleifera Leaf Extracts Against Liver Injury Induced by Artesunate-amodiaquine Antimalarial Combination

Abstract

Malaria is a mosquito-borne disease caused by plasmodium falciparum parasites. It is treated using antimalarial agents. In malaria endemic countries such as Kenya, self-medication with antimalarial agents is rife. This increases the likelihood of occurrence of severe adverse effects associated with drug misappropriation. Artesunate-amodiaquine (AS-AQ) is an antimalarial combination currently in use for malaria therapy. This combination causes liver damage, neurotoxicity, agranulocytosis and haemolytic anaemia as adverse effects. These effects have been shown to be due to the free radicals generated by the drug. Plants with antioxidant effects may be used to alleviate the adverse effects of AS-AQ. Moringa oleifera (MO) is a plant that originates in Asia but is nowadays extensively cultivated in the tropics and sub-tropics. The plant is claimed to have antioxidant properties and other medicinal values. The antioxidant and` hepatoprotective effects of this plant are some of the medicinal claims that have not been fully investigated although scanty literature is available on these claims. The objective of the current study was to evaluate the antioxidant capacity and hepatoprotective potential of leaf extracts of MO against liver degradation caused by AS-AQ antimalarial combination. The leaves of MO were obtained from a plantation of the plant in a farm of the University of Nairobi located at Kibwezi in Makueni county. Water (AQ) and aqueous-methanol (AQ-ME) leaf extracts were prepared. Qualitative phytochemical analysis was performed on both extracts to identify compounds of pharmacological value. The antioxidant capacity of these extracts was then assessed in vitro by preparing calibration curves of the antioxidant standards; gallic acid, catechin, ascorbic acid, ethylene diamine tetra acetic acid and butylated hydroxy toluene using a UV-Visible xv spectrophotometer and thereafter extrapolating the concentration of the antioxidants in the extracts from these curves. The results of these in vitro assays informed the decision of the extract to be selected for testing in vivo hepatoprotective efficacy in female albino rats. Acute oral toxicity of the selected extract was evaluated using the limit test dose of the up and down procedure based on OECD guidelines. From acute oral toxicity results, a safe dose (1000mg/kg) was selected and evaluated for hepatoprotective activity against AS-AQ induced toxicity in female rats using the biochemical parameters aspartate amino transferase (AST), alanine amino transferase (ALT) and total bilirubin (TB) as well as histopathological examination of rat liver sections. The extraction yield of the AQ and AQ-ME extracts was 14 % and 18 % respectively. Qualitative phytochemical screening of the extracts revealed the presence of alkaloids, cardiac glycosides, flavonoids, phenolics, saponins, tannins and ascorbic acid in both extracts. The total content of phenolics in the AQ and AQ-ME extracts was 35.42 ± 5.80 and 52.04 ± 3.13 milligrams of gallic acid equivalents (GAE) per gram of the dry plant material respectively and the total content of flavonoids was 78.69 ± 13.04 and 365.52 ± 86.76 milligrams of catechin equivalents (CE) per gram of the dry plant material respectively while the content of ascorbic acid was 2.02 ± 0.66 and 3.04 ± 2.06 milligrams of ascorbic acid equivalents (AAE) per gram of the dry plant material respectively. The LD50 of the AQ-ME extract was found to be > 2000mg/kg. A 1000mg/kg dose of the AQ-ME extract lowered the serum ALT and total bilirubin non-significantly (p>0.05) but significantly (p<0.05) lowered the AST levels to values comparable to those of the standard hepatoprotectant, siliphos®. The AQ-ME extract reduced the histological distortion of liver cells in the experimental rats induced by high doses of AS-AQ. The findings of this study suggest xvi that the bio protective activity of the leaves of MO may have some relation to its antioxidant properties which are attributable to the phenolic, flavonoid and ascorbic acid contents. Thus, leaves of MO may be useful in the mitigation of free-radical initiated disease conditions. Keywords; Moringa oleifera, antioxidant potential, hepatoprotective capacity, artesunate-amodiaquine, albino rats, liver