The development of antibiotic resistant bacteria stems from a number of factors, including inappropriate use of antibiotics in human and animal health and their prolonged use as growth promoters at sub-clinical doses in poultry and livestock production. We were interested in investigating plants that could be useful in protecting humans or animals against diarrhoea. We decided to work on extracts of nine plant species with good activity against Escherichia coli based on earlier work in the Phytomedicine Programme. Leaves of nine medicinal plant species with high antibacterial activity against Escherichia coli were extracted with acetone and their minimal inhibitory concentration (MIC) values determined using a microplate serial dilution technique against Gram-positive (Staphylococcus aureus, Enterococcus faecalis and Bacillus cereus) and Gram-negative (Escherichia coli, Salmonella Typhimurium and Pseudomonas aeruginosa) bacteria. Bioautography was used to determine the number of bioactive compounds in each extract. In vitro safety of the extracts was determined using the 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide reduction assay on Vero cells. The extracts were active against all the pathogens with average MICs ranging from 0.02 to 0.52 mg/ml. As expected E. coli was relatively sensitive, while E. faecalis and S. Typhimurium were more resistant to the extracts (average MICs of 0.28 mg/ml and 0.22 mg/ml respectively). Cremaspora triflora and Maesa lanceolata leaf extracts had higher activity than the other extracts against Gram-positive and Gram-negative pathogens with mean MICs of 0.07 mg/ml and 0.09 mg/ml respectively. Extracts of Maesa lanceolata and Hypericum roeperianum had the highest total antibacterial activity (TAA) at 1417 and 963 ml/g respectively. All extracts with the exception of that of Maesa lanceolata, Elaeodendron croceum and Calpurnia aurea had relatively low cytotoxicity with LC50 > 20 μg/ml. Cremaspora triflora had the best selectivity index (SI) against S. aureus and E. coli of 2.87 and 1.15 respectively. Hypericum roeperianum had a SI of 1.10 against B. cereus. Bioautography revealed 1–6 visible antimicrobial compounds that were generally non-polar. There was a weak positive, but statistically non-significant correlation between the potency of the extracts and their cytotoxicity (R = 0.45, ρ > 0.05). The activity of the extracts on the test bacteria was in some cases not correlated with cytotoxicity, as shown by selectivity indices >1. This means that cellular toxicity was probably not due to compounds with antibacterial activity. Some of the extracts had a good potential for therapeutic use against the bacterial pathogens or for application in treating diarhoea. It does not appear that activity against E. coli is a good predictor of activity against Gram-negative rather than Gram-positive bacteria. Further investigation is in progress on C. triflora and H. roeperianum, both of which had promising activities and potential safety based on cytotoxicity.

Oxidative stress predisposes the human and animal body to diseases like cancer, diabetes, arthritis, rheumatoid arthritis, atherosclerosis and chronic inflammatory disorders. Hence, this study seeks to determine the antioxidant, anti-inflammatory and anti-arthritic activities of acetone leaf extracts of nine South African medicinal plants that have been used traditionally to treat arthritis and inflammation. The anti-inflammatory activity of the extracts was determined by investigating inhibition of nitric oxide production in lipopolysaccharide activated RAW 264.7 macrophages as well as 15-lipoxygenase enzyme inhibition. An anti-protein denaturation assay was used to determine the anti-arthritic properties of the extracts. The antioxidant activity was determined using the 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2′-azino-bis (3-ethyl-benzthiazoline-6-sulfonic acid) (ABTS) radical scavenging assays and ferric reducing antioxidant power (FRAP). The total phenolic and total flavonoid concentration of extracts were determined by using standard methods. All extracts inhibited nitric oxide production in a dose-dependent manner in the LPS-stimulated RAW 264.7 macrophages. Extracts of Maesa lanceolata and Heteromorpha arborescens inhibited NO production by 99.16 % and 89.48 % at a concentration of 30 μg/ml respectively. Elaeodendron croceum and Calpurnia aurea extracts had strong activity against 15-lipoxygenase activity with IC50 values of 26.23 and 34.70 μg/ml respectively. Morus mesozygia and Heteromorpha arborescens extracts had good in vitro anti-arthritic activity with IC50 values of 11.89 and 53.78 μg/ml, the positive control diclofenac sodium had IC50 value of 32.37 μg/ml. The free radical scavenging activity of the extracts in DPPH assays ranged between 7.72 and 154.77 μg/ml. Trolox equivalent antioxidant capacity (TEAC) and FRAP values ranged from 0.06 to 1.32 and 0.06 to 0.99 respectively. Results from this study support the traditional use of the selected medicinal plants in the management of arthritis and other inflammatory conditions. The free radical scavenging capacity of the extracts may be related to an immune boosting potential.

The use of medicinal plants in the treatment of diseases has generated renewed interest in recent times, as herbal preparations are increasingly being used in both human and animal healthcare systems. Diarrhoea is one of the common clinical signs of gastrointestinal disorders caused by both infectious and non-infectious agents and an important livestock debilitating condition. Plateau State is rich in savannah and forest vegetations and home to a vast collection of plants upheld in folklore as having useful medicinal applications. There is however scarcity of documented information on the medicinal plants used in the treatment of animal diarrhoea in the state, thus the need for this survey. Ten (10) out of 17 Local Government Areas (LGAs), spread across the three senatorial zones were selected. Farmers were interviewed using well structured, open-ended questionnaire and guided dialogue techniques between October and December 2010. Medicinal plants reported to be effective in diarrhoea management were collected using the guided field-walk method for identification and authentication.

The One Health concept considers the interconnectivity, interactions and interdependence of humans, animals and the environment. Humans, animals and other organisms are constantly exposed to a wide range of natural toxins present in the environment. Thus, there is growing concern about the potential detrimental effects that natural toxins could pose to achieve One Health. Interestingly, alkaloids, steroids and bioactive peptides obtained from natural toxins could be used for the development of therapeutic agents. Our literature search focused on the following keywords; toxins, One Health, microbial toxins, mycotoxins, phytotoxins, phycotoxins, insect toxins and toxin effects. Google Scholar, Science Direct, PubMed and Web of Science were the search engines used to obtain primary databases. We chose relevant full-text articles and review papers published in English language only. The research was done between July 2022 and January 2023. Natural toxins are poisonous substances comprising bioactive compounds produced by microorganisms, invertebrates, plants and animals. These compounds possess diverse structures and differ in biological function and toxicity, posing risks to human and animal health through the contamination of the environment, causing disease or death in certain cases. Findings from the articles reviewed revealed that effects of natural toxins on animals and humans gained more attention than the impact of natural toxins on the environment and lower organisms, irrespective of the significant roles that lower organisms play to maintain ecosystem balance. Also, systematic approaches for toxin control in the environment and utilization for beneficial purposes are inadequate in many regions. Remarkably, bioactive compounds present in natural toxins have potential for the development of therapeutic agents. These findings suggest that global, comprehensive and coordinated efforts are required for improved management of natural toxins through an interdisciplinary, One Health approach. Adopting a One Health approach is critical to addressing the effects of natural toxins on the health of humans, animals and the environment.