Preliminary laboratory assessment of the crude aqueous and ethanolic extracts of Dalbergia sissoo plant parts for molluscicidal, ovicidal and cercaricidal activities

Abstract

This study evaluated the molluscicidal, ovicidal and cercaricidal properties of the crude aqueous and ethanolic extracts of Dalbergia sissoo Roxb. 1832, a Nigerian plant species used in alternative medicine as anthelmintic/vermifuge. Using the WHO (1983) protocol for the testing of molluscicides, laboratory-bred adult Biomphalaria pfeifferi (Krauss, 1848), the snail intermediate host of Schistosoma mansoni (Sambon, 1907) in Nigeria and their viable 0–24 h old egg masses, were separately exposed to five different concentrations (7.81–2000 mg l −1 ) each, of the crude aqueous and ethanolic extracts of the fruits, leaves, roots and stem bark of D. sissoo , for 24 h. Freshly harvested cercariae obtained from snails infected with 6-7 miracidia of S. mansoni , were similarly exposed (7.81–4000 mg l −1 ) for 15–120 min. The LC 50 and LC 90 values of each extract for target organisms were calculated using probit analysis. Although all aqueous and ethanolic extracts of the leaves and stem bark as well as all aqueous extracts of the fruits and root, demonstrated molluscicidal properties, their 24 h-LC 90 values were significantly higher than 100 mg l −1 . Only the ethanolic extracts of the fruits and roots had significant LC 90 values −1 (74.33 and 93.93 mg l −1 , respectively). Snail exposure to test extracts caused behavioural changes which were concentration-dependent. The calculated 24 h-LC 50 and LC 90 values of the extracts for the eggs of B. pfeifferi varied from 39.91–861.47 mg l −1 and 89.29–2200.75 mg l −1 , respectively. Egg mortalities were manifested at the gastrula/exogastrula stage and or the prehatch snail stage of development, depending on concentration. Results of cercaricidal tests showed progressive declines in cercarial motility as the concentrations of extracts and exposure time increases. The crude ethanolic extracts of D. sissoo fruits and roots exhibited promising molluscicidal activities (LC 90 values −1 ) and also demonstrated additional toxicities towards 0–24 h-old egg masses of B. pfeifferi and cercariae of S. mansoni .