Abstract
Aim of the studyIn southern Africa many plant species are used to treat different ailments and diseases related to infections. Diarrhoea is not only an important disease of humans but also causes large losses in the animal production industry. The antimicrobial activity of many of these species may however, be based on their tannin content. Even though high tannin content may be therapeutically effective against pathogens causing diarrhoea, nutritional side effects limit its prophylactic use in animal production. The aims of the study were two-fold. In the first place it was to compile a list of species used traditionally to treat diarrhoea. The second aim was to identify and remove those species where a potential antidiarrhoeal activity may be due to tannins, because it would be counterproductive to use in production animal systems. Materials and methodsAfter a literature study, 53 tree species used to treat diarrhoea or dysentery in humans or animals in southern Africa were identified. Plant material was collected and dried powdered leaves were extracted with acetone. To select plants with potential use as prophylactics against diarrhoea, the tannin content was determined by a radial diffusion method of precipitation of bovine serum albumin in agar and expressed as gallic acid equivalents. ResultsBased on our literature research plant species from at least 37 tree families are used traditionally to treat diarrhoea in southern Africa. Most of the species were from the Fabaceae (9), Euphorbiaceae (6), Anacardiaceae (3) and Combretaceae (3). The highest tannin content of 11.3mg/ml gallic acid equivalents was detected in leaf extracts of Combretum molle and Sclerocarya birrea. About 40% of the species tested contained no tannin based on the assay used. ConclusionsAs other authors have found, the tannin content within a family varied strongly. Therefore it is dangerous to make any conclusions on the tannin content of the same plant family. About 42% of the species had no detectable tannin content and another 25% contained 0–2mg/ml gallic acid equivalent tannins. In general it appears that in most cases tannins do not play a major role in treating diarrhoea in southern African ethnomedicine. If aqueous extracts were used, the situation could have been different.
Highlights
Diarrhoea often leads to reduced growth of animals or even to their death, as well as to high treatment costs and an economic loss for the farmer
This has led to the ban of antibacterial growth promoters that might interfere with human chemotherapy in European Union countries (Witte, 2000)
With values as high as 22% for Terminalia sericea and a higher value for Combretum zeyheri (6.6% compared to the 2.9% found here)
Summary
Diarrhoea often leads to reduced growth of animals or even to their death, as well as to high treatment costs and an economic loss for the farmer To address this problem, antibiotic feed additives were developed. Selective pressure exerted by the use of antibiotics as growth promoters in food animals appears to have created large reservoirs of transferable antibiotic resistance in these ecosystems (Witte, 2000) This has led to the ban of antibacterial growth promoters that might interfere with human chemotherapy in European Union countries (Witte, 2000). Following the ban, countries outside the EU will find it difficult to continue exporting animal products such as poultry and pork meat This opens up new opportunities for developing alternative feed additives
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
