Snake-Antivenom Activity of Selected Medicinal Plant Extracts from Turkana and Uasin-Gishu Counties of Kenya
Yego, Kennedy Kimurgor
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The present management regime of snake bites requires the use of antivenom immunoglobulins. However, these antivenoms have the limitations of being expensive, requiring cold storage facilities and have problems of hypersensitivity reactions in some individuals. A. spinosus, C. articulatus, C. spinarum, C. molle and R. usambarensis have been used traditionally in the management of snake bites in Turkana and Uasin-Gishu Counties, Kenya. However, their efficacy and safety have not been scientifically validated. The aim of this study was therefore to determine in vivo and in vitro efficacy and safety of these selected medicinal plants using the mouse model, agarose-erythrocyte-egg yolk gel plate and human citrated plasma methods. Relevant plant parts from these medicinal plants were collected, dried under shade, crushed into powder and then extracted with distilled water. The potency of the antivenom activity of the plant extracts was estimated by determining the least dose of venom required to kill 50% of the mice (LD50) and the dose of the extract required to protect half the animals (ED50) in a statistically significant group of animals from two times the LD50. The antivenom studies suggest that the aqueous plant extracts possess antivenom activity against Naja subfulva venom both in vivo and in vitro. Evaluation of acute and sub-acute toxicity studies indicated no lethality after intraperitoneal administration of the extracts in mice at 1600, 2500 and 5000 mg/kg body weight. Repeated daily oral administration (sub-acute studies) of the five aqueous plants extracts at 10, 300 and 1000 mg/kg body weight to mice for 14 days demonstrated significant decreases in the average weekly body weight, increases in percent organ to body weight, decreases in several biochemical analytes and enzymes, and increases in white blood cell and differential white blood cell count. However, no changes in the level of red blood cells, hemoglobin and the related indices were observed except for C. spinarum extract-treated mice where red blood cells, hemoglobin and packed cell volume were decreased. Phytochemical screening of the five aqueous plants extracts demonstrated the presence of phenols, alkaloids, flavonoids, flavones, steroids, terpenoids, triterpenoids, tannins, saponins and cardiac glycosides. Of the seventeen mineral elements levels estimated in the five aqueous plants extracts, twelve were below the recommended daily allowances and five were above the recommended daily allowances. In conclusion, the aqueous extracts of A. spinosus, C. articulatus, C. spinarum, C. molle and R. usambarensis, neutralized snake venom activity of Naja subfulva and demonstrated toxicity in the subacute toxicity studies. The observed antivenom activity and subacute toxicity could be explained by the phytochemicals and mineral elements present in these five aqueous plants extracts from Turkana and Uasin-Gishu counties. The five studied plants could therefore be used at the tested extract efficacy doses.