Screening of 16 poisonous plants for antibacterial, anthelmintic and cytotoxic activity in vitro

Acetone extracts of the leaves of 16 plants known to have toxic effects when ingested by livestock were screened for biological activity, on the basis that toxic plants have proven pharmacological activity. The plants were tested for antibacterial effects against two Gram-negative (Escherichia coli and Pseudomonas aeruginosa) and two Gram-positive (Enterococcus faecalis and Staphylococcus aureus) bacteria. Anthelmintic activity against the free-living test nematode Caeno-rhabditis elegans was assessed. The potential cytotoxicity of the extracts was investigated using the brine shrimp lethality assay. Gossypium herbaceum, Lantana camara, L. rugosa, Thevetia peruviana and Sorghum bicolor inhibited the growth of all test bacteria with MIC values ranging from 0.39mg ml− 1 to 6.3mg ml− 1. A few plants, namely Gossypium herbaceum, Hertia pallens, Jatropha multifida and Lantana rugosa, showed notable effects against the nematodes at a concentration of 1mg ml− 1. Only Hertia pallens (LC50 = 0.54mg ml− 1) and Lantana rugosa (LC50 = 0.69mg ml− 1) exhibited cytotoxic activity as indicated by the brine shrimp assay. These results establish the limited applicability of the brine shrimp assay to determine the toxicity of plant extracts.