This study investigated the acute toxicity of aqueous and ethanol extracts of eleven Jamaican medicinal plants against Thiara granifera (Lamarck, 1758). The plants were Annona muricata L., Blighia sapida Koenig, Croton linearis Jacq., Eupatorium odoratum L., Ficus benjamina L., Gossypium barbadense L., Guaiacum officinale L., Pithecellobium unguis-cati (L.) Benth., Psidium guajava L., Sida acuta Burm. and Terminalia catappa L. Extracts with a 24hr LC50 value greater than 50 mgL-1 or a 24hr LC90 value greater than 100 mgL-1 were deemed to lack significant molluscicidal activity. G. officinale, C. linearis, E. odoratum and P. unguis-cati were highly active. The potencies as indicated by the 24hr LC50 values (mgL-1) in brackets, of the aqueous and ethanol extracts were in the order: G. officinale (1.7) > C. linearis (29.1) > E. odoratum (54.1), and P. unguis-cati (3.0) > G. officinale (7.6) > E. odoratum (27.6), respectively. The aqueous extract of G. officinale and the ethanol extracts of G. officinale and P. unguis-cati were more potent than the synthetic molluscicide, Plantgard Slug and Snail Liquid® (24hr LC50 = 18.3 mgL-1). The secondary metabolites of the aqueous and ethanol extracts of G. officinale, C. linearis and E. odoratum were also investigated. The aqueous extracts all contained saponins, alkaloids and triterpenes. The ethanol extracts contained saponins, tannins, flavonoids, triterpenes, steroids and reducing compounds for G. officinale, saponins, flavonoids, triterpenes and steroids for C. linearis and flavonoids, triterpenes and steroids for E. odoratum.
Keywords: Acute toxicity, medicinal plants, secondary metabolites, Thiara granifera.