Effects of n-hexane, Ethyl Acetate and Methanol bark extracts of <i>Entada africana</i> Guill. & Perott. (Fabaceae) on the Snail <i>Bulinus globosus</i>

Abstract

Cases of schistosomiasis have assumed global public health significance, especially in Africa and sub-Saharan Africa (SSA); ranking  second to malaria as a neglected tropical disease (NTD). Control of this disease is majorly by the use of synthetic molluscicides, which are  known to cause ecotoxicity, with a long-term effect on human health. Besides, most synthetic molluscicides are often unaffordable by the  locals. Many of them do not have the technical knowledge of application, yet are continuously involved in activities that prone them  to re-infection by schistosomes. This study aimed to ascertain the molluscicidal effects of Entada africana (E. africana) stems bark solvent  extracts on Bulinus globosus. The stem bark of E. africana was obtained by successive cold extraction, using non-polar and polar solvents.  After running the phytochemical analysis, B. globosus adult snails were challenged with serialized concentrations of n-hexane,  ethyl acetate and methanol extracts, comparable to negative and positive controls. Data were analysed by use of GraphPad® Prism  version 8.4. Molluscicidal activities showed that methanol extract had the highest bioactivity (86.67±11.55 – 100.00±0.00), followed by n-hexane (56.67±5.77 – 100.00±0.00) and the least, ethyl acetate (46.67±5.77 – 80.00±10.00). There was a significant difference at p ≤ 0.05,  (LSD 8.38), of molluscicidal activities. The LC and LC values were (46.88/128.57; 9.38/93.10; and 50 90 7.89/38.58) for ethyl acetate,  n-hexane, and methanol respectively, at 24h post-exposure (PE). Methanol extract had 100% mortality at 50-100mg/L, 95% (CI -20.24 to  0.24), and compared favourably to the positive control, which had 100% mortality. The study concludes that E. africana stem bark  methanolic extract had the most bioactive properties and can be used as a molluscicidal agent in combating B. globosusintermediate  host of S. haematobium schistosome.