Ethnobotanical study of plants from Pondoland used against diarrhoea.

Abstract

Diarrhoea and related diseases are the most common causes of death in children, especially from developing countries, killing about 1.5 million children under the age of five yearly. In South Africa, diarrhoea is the third leading cause of death. This condition results from food and water sources infected with Campylobacter spp., Escherichia coli, Salmonella spp., Shigella spp., Giardia intestinalis and Cryptospondium parvum amongst others. Diarrhoea spreads through faeces-contaminated water. Hence, infection is more common when there is a short supply of clean drinking and cooking water. Waterborne diseases are common in rural communities of Bizana because the majority of rural dwellers depend largely on water from unprotected sources. Most of the pathogens that cause diarrhoea have developed resistance to several antibiotics. Therefore there is a need for new and safe antidiarrhoeal drugs. Most people in developing countries use traditional medicine to treat all kinds of diseases including diarrhoea and South Africa is no exception. Each cultural group in South Africa has different medical solutions for the prevention and curing of the same disease. The people from Pondoland (AmaMpondo), around Bizana have a strong tradition of using medicinal plants for the cure and prevention of several conditions including diarrhoea. Although several researchers have conducted different types of studies in many parts of South Africa to evaluate the efficacy of traditional medicine used in the treatment of diarrhoea, there is, however, still a lot of undisclosed data that should be collected. The aims of this research were to record and collect medicinal plants that are used for treating diarrhoea in Bizana, Pondoland in the Eastern Cape and evaluate them for their pharmacological properties. An ethnobotanical approach is one of several methods that have been useful in selecting plants for pharmacological research, yielding better results than other plant selection methods. Using questionnaires, this approach was used to record plants that are used for treating diarrhoea in Bizana for testing in pharmacological assays. From the completed questionnaires, nine plants were selected for bioassays based on their higher frequency index, and the fact that the plants have never been evaluated against diarrhoea causing-microorganisms. The study revealed 34 plant species belonging to 21 families as being used in treatment of diarrhoea in the study area. Psidium guajava was the most mentioned plant species. The dried, ground plant materials were each extracted non-sequentially using petroleum ether (PE), dichloromethane (DCM), 70% ethanol (EtOH) and water. Among all the extracts, 70% ethanol yielded the highest quantity of crude extract. The extracts were each evaluated for their antibacterial, anti-inflammatory and genotoxicity properties. For the antibacterial activity, the following diarrhoea causing microorganisms were used: Gram-positive Staphylococcus aureus and Gram-negative Campylobacter jejuni, E. coli and Shigella flexneri. A microdilution assay (for S. aureus, E. coli and S. flexneri) and the disk diffusion technique (for C. jejuni) were used for antibacterial testing. The extracts were also evaluated for their ability to inhibit cyclooxygenase (COX-1 and -2) enzymes. Genotoxicity was evaluated using the Salmonella microsome assay without S9 metabolic activation. Three strains of Salmonella typhimurium TA98, TA1535 and TA1537 were used. The evaluated plant extracts showed a broad spectrum of inhibitory activity with MIC values ranging from 0.098-12.5 mg/ml and mean zone inhibition percentage ranging from 0-73%. The best activity was exhibited by DCM extracts of Rapanea melanophloeos, EtOH extracts of Ficus craterostoma and Maesa lanceolata with MIC values of 0.098 mg/ml and EtOH extracts of Searsia chirindensis with 73% mean zone inhibition percentage. The inhibitory activity against COX-1 enzyme was higher than COX-2, with 19 plant extracts for the former and 7 for the latter. The highest inhibition of COX-1 was shown by EtOH extracts of F. craterostoma and the DCM extract of S. chirindensis at 100%. Highest percentage COX-2 inhibition was shown by water extracts of F. craterostoma and DCM extracts of Tecoma capensis with 99.5% and 99.0% respectively. None of the tested plant extracts were mutagenic, at all concentrations tested against all tester strains of the bacteria. The results of this study demonstrate that people still have a rich and diverse pool of knowledge concerning the uses of plants against diarrhoea. The data also show that plants form part of the cultural heritage of the communities in Pondoland. Therefore it is important to urgently save the people’s cultural heritage by recording the existing knowledge and confirming therapeutic uses of plants through scientific methods. This will prevent the information from vanishing together with the ageing knowledge holders. In light of the fact that the evaluated plants were selected based on their ethnobotanical use for treating diarrhoea, the activities reported here goes a long way in adding value to the plants used as part of traditional medicine.