Phytochemical Screening and Anthelmintic Activity of Entada leptostachya (Harms) and Rapanea rhododendroides (L.) Mez against Haemonchus contortus

Abstract

Haemonchus contortus is parasitic helminths of the sheep capable of causing acute and high mortality. Control of gastrointestinal helminths infection in livestock relies mainly on the use of synthetic anthelmintics. However, these broad spectrum drugs are expensive, inaccessible or inadequately available to farmers in remote poor settings. The problem with synthetic anthelmintics is further compounded by development of anthelmintic resistance. The present study investigated the phytochemistry and anthelmintic activity of aqueous and solvent extracts (hexane, acetone and methanol) of root bark of Entada leptostachya (Harms) and stem bark of Rapanea rhododendroides (L.) Mez. To achieve the objectives, brine shrimp lethality test using brine shrimp (Artemia salina) larvae was used to determine the toxicity of the aqueous and organic extracts with modifications. The worm motility inhibition assay was utilized in order to investigate the direct effects of the plant extracts on the survival of adult worms of H. contortus. Four concentrations (12.5, 25, 50 and100 mg/ml) of each extract were studied in the bioassay. The Extracts of E. leptostachya exhibited higher toxicity and anthelmintic activity compared to those of R. rhododendroides. Methanolic extracts for both E. leptostachya and R. rhododendroides were more potent against H. contortus adult worms exhibiting 70 and 50 % mortality respectively. Hexane extracts of both E. leptostachya (20 %) and R. rhododendroides (10 %) were the least potent. Methanol and aqueous extracts of E. leptostachya showed brine shrimp lethality of 1.1 and 2.7 g/ml, respectively. E. leptostachya and R. rhododendroides methanolic extracts have significant anthelmintic activity (70 and 50 %) and have potential for development of new anthelmintic drugs. Saponins, tannins and flavonoids were some of the phytochemicals identified in the extracts. Oleanolic acid was isolated from E. leptostachya methanol extract using chromatographic techniques and characterized using spectroscopic techniques (IR, UV and MS). The data revealed the dose- dependent anthelmintic activity in the in vitro studies. There were notable anthelmintic activities by all extracts. Methanol extract of Entada leptostachya showed the highest anthelmintic activity and therefore it can be used as a lead compound to prepare anthelmintic drugs.