In vitro biological activities of selected plant species used in traditional livestock medicine in Zimbabwe: A useful step in the quest for novel therapeutic options against some bacterial infections of economic importance in goats

• Bioactivity was tested of five plants used in traditional goat medicine in Zimbabwe. • S. singueana and E. abyssinica extracts had various bioactivities with low toxicity. • The best anti-lipoxygenase activity was yielded by E. divinorum acetone extract. • Some plants could be developed into widely used and accepted livestock treatments. The search for novel antibacterial agents in livestock is prompted by the scourge of antibiotic resistance and costly nature of conventional drugs. Potential antibacterial alternatives should be cheap, safe and therapeutically active. Biological activities of five selected ethnobotanical plant species ( Euclea divinorum Hiern., Kigelia africana (Lam.) Benth., Senna singueana (Delile) Lock, Cassia abbreviata Oliv. and Erythrina abyssinica Lam . ) were investigated. The serial microdilution assay was used to evaluate antibacterial activities of extracts against six bacterial strains ( Salmonella Typhimurium , Clostridium perfringens, Corynebacterium pseudotuberculosis, Salmonella Enteritidis , Escherichia coli and Staphylococcus aureus ). Antioxidant and anti-lipoxygenase activities were evaluated using the free radical scavenging and ferrous oxidation-xylenol orange assays, respectively. The tetrazolium-based colorimetric (MTT) reduction assay was used to assess cytotoxicity of extracts. Acetone extracts of S. singueana and E. abyssinica had broad spectrum antibacterial activity (MIC < 100 µg/ml; total activity > 1000 mg/g). All acetone extracts had substantial antibiofilm activity against at least one of the tested bacterial strains (≥ 50 % inhibition). Acetone and DCM/methanol extracts of S. singueana and the DCM/methanol extract of E. abyssinica had the best antioxidant capacity. The LC 50 values were similar to those of the positive controls (P > 0.05). The best anti-lipoxygenase activity was shown by acetone extracts of E. divinorum (LC 50 = 4.67 ± 0.08 µg/ml). All extracts tested were less toxic than the control anticancer agent, doxorubicin (P < 0.05). In conclusion, acetone extracts of S . singueana, E. abyssinica and E. divinorum had a cocktail of therapeutic activity and could be leads in the development of useful livestock antibacterial drugs.