Investigating antimicrobial compounds in South African Combretaceae species using a biochemometric approach.

ETHNOPHARMACOLOGICAL RELEVANCE: Many species within the family Combretaceae are popular medicinal plants that are used traditionally to treat various conditions, of which many are related to bacterial infections. Global concerns regarding the increasing resistance of pathogens towards currently available antibiotics have encouraged researchers to find new drugs with antibacterial activity, particularly from plant sources. AIM OF THE STUDY: This study was aimed at exploring the broad-spectrum antibacterial potential of methanol extracts of species representing four genera of Combretaceae (Combretum, Pteleopsis, Quisqualis, Terminalia), indigenous to South Africa, using a biochemometric approach. MATERIALS AND METHODS: The microdilution assay was used to determine the antibacterial activities, measured as minimum inhibitory concentrations (MICs), of the 51 methanol extracts representing 35 Combretaceae species, against nine species of pathogenic bacteria. Integrative biochemometric analysis was performed, thereby correlating the MIC values with the metabolomic data obtained from ultra-performance liquid chromatography-mass spectrometry (UPLC-MS) analysis. Orthogonal projections to latent structures-discriminant analysis (OPLS-DA) models were constructed for six pathogens displaying variation in their susceptibility towards the extracts. RESULTS: Evaluation of the overall MIC values obtained indicated that extracts of species from the four genera displayed the highest activity towards Bacillus cereus ATCC 11778 (average MIC 0.52 mg/mL) and Salmonella typhimurium ATCC 14028 (average MIC 0.63 mg/mL). These bacteria were the most sensitive Gram-positive and Gram-negative bacteria, respectively. Extracts from Combretum acutifolium, Combretum imberbe and Combretum elaeagnoides were the most active, with average MIC values of 0.70 mg/mL, 0.52 mg/mL and 0.45 mg/mL, respectively. Five triterpenoid compounds were tentatively identified as biomarkers from the biochemometric analysis. CONCLUSION: Correlation of the phytochemistry of species from four genera in the Combretaceae family with antibacterial activity revealed that triterpenoids are responsible for the broad-spectrum antibacterial activity observed.

Acetone leaf extracts of some South African trees with high activity against Escherichia coli also have good antimycobacterial activity and selectivity index.

BACKGROUND: Tuberculosis is a world-wide problem affecting humans and animals. There is increasing development of resistance of the pathogens to current antimycobacterial agents. Many authors have investigated activities of extracts and isolated compounds from plants. The traditional uses of plants have frequently been the criterion to select plants investigated. In this contribution, we investigate whether plant extracts with very good activity against Escherichia coli may also be active against mycobacteria. METHODS: The antimycobacterial activity of eight South African tree leaf extracts with high activity against Escherichia coli were determined in vitro against Mycobacterium smegmatis, M. fortuitum and M. aurum, using a serial microdilution method. The cellular cytotoxicity was also determined by the MTT assay using Vero monkey kidney cells. The selectivity index was determined by dividing the cytotoxicity of extracts by MIC. RESULTS: The antimycobacterial activity of the extracts ranged from 0.02 to 2.5 mg/ml. Mycobacterium smegmatis was more sensitive to the extracts (Average MIC = 0.96 mg/ml) and Mycobacterium aurum was comparatively resistant (Average MIC = 2.04 mg/ml). The extracts of Cremaspora triflora had strong antimycobacterial activity with a MIC of 0.05 mg/ml that compared reasonably well with that of streptomycin (0.01 mg/ml) and rifampicin (0.03 mg/ml), p > 0.05. Cremaspora triflora had the best selectivity index of 2.87 against Mycobacterium fortuitum. CONCLUSION: The high activity of C. triflora extracts against the fast-growing mycobacteria and good cellular safety is promising. It may be interesting to investigate extracts against pathogenic M. tuberculosis, M. bovis and M. avium cultures and to isolate active antimycobacterial compounds.

Potency and selectivity indices of acetone leaf extracts of nine selected South African trees against six opportunistic Enterobacteriaceae isolates from commercial chicken eggs.

BACKGROUND: The rise in antimicrobial resistance in a plethora of nosocomial and opportunistic bacterial pathogens often isolated from commercial eggs, poses a serious public health concern. The existence of these contaminants may also serve as a drawback in the current efforts of improving the well-being of immunocompromised patients. The aim of this study was to determine the efficacy of plant extracts that had good activity on Escherichia coli in previous word on pathogens isolated from eggs for possible use in combating pathogens from eggs. METHODS: Acetone leaf extracts of nine trees with good activities against Escherichia coli were tested for their in vitro antibacterial activity against six opportunistic bacterial isolates from commercial eggs (Stenotrophomonas maltophilia, Klebsiella pneumoniae, Salmonella serotype Typhimurium, Proteus mirabilis, Enterobacter cloacae and Escherichia coli) using a serial microdilution method with tetrazolium violet as indicator of growth. Cytotoxicity was determined using a tetrazolium-based colorimetric assay against Vero kidney cells, and selectivity index calculated. RESULTS: The MIC values range of the different extracts against Stenotrophomonas maltophilia was 0.08-0.31 mg/ml, Klebsiella pneumonia 0.08-0.63 mg/ml, Salmonella ser. Typhimurium 0.08-0.63 mg/ml, Proteus mirabilis 0.02-1.25 mg/ml, Enterobacter cloacae 0.08-0.31 mg/ml and Escherichia coli 0.08-0.16 mg/ml respectively. Escherichia coli was the most sensitive while Proteus mirabilis was most resistant pathogen to the different test extracts, with mean MIC values of 0.08 mg/ml and 0.46 mg/ml respectively. Cremaspora triflora extracts had good activity against all the pathogenic egg isolates, with the exception of Proteus mirabilis. Maesa lanceolata and Elaeodendron croceum had the best total antibacterial activity (TAA), while generally the selectivity index of the extract was low (SI < 1). CONCLUSION: The exceptional activity of C. triflora extracts suggests that the plant has potential as a therapeutic agent against some members of the Enterobacteriaceae. Further pharmacological investigations may be interesting in the search for new antimicrobial leads.

Ethnobotanical survey of medicinal plants used in the treatment of animal diarrhoea in Plateau State, Nigeria.

BACKGROUND: 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. RESULTS: A total of 248 questionnaires were completed, out of which 207 respondents (83.47%) acknowledged the use of herbs in diarrhoea management, while 41 (16.53%) do not use herbs or apply other traditional methods in the treatment of diarrhoea in their animals. Medicinal plants cited as beneficial in the treatment of animal diarrhoea numbered 132, from which 57(43.18%) were scientifically identified and classified into 25 plant families with the families Fabaceae (21%) and Combretaceae (14.04%) having the highest occurrence. The plant parts mostly used in antidiarrhoeal herbal preparations are the leaves (43.86%) followed by the stem bark (29.82%). The herbal preparations are usually administered orally. CONCLUSION: Rural communities in Plateau State are a rich source of information on medicinal plants as revealed in this survey. There is need to scientifically ascertain the authenticity of the claimed antidiarrhoeal properties of these plants and perhaps develop more readily available alternatives in the treatment of diarrhoea.