Evaluation of plants used in African traditional medicine for asthma and related conditions.
Motlhatlego, Katlego Ellena.
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Traditional medicine is a form of discipline that has been applied within most South African societies with the objective of enhancing the physical and psychological health system in the country. Asthma is a complex inflammatory disease that involves the narrowing of the airways. The prevalence of asthma is increasing worldwide, and this chronic disease has been identified as a significant cause of morbidity and mortality. Asthma poses a major threat to health across the population of South Africa. The adverse effects of current treatments have encouraged the use of traditional medicine. The primary aim of the research study was to evaluate the efficacy of plants used in African traditional medicine against asthma and chest infections. This was achieved by screening Adansonia digitata, Ballota africana, Catha edulis, Datura stramonium, Pelargonium sidoides, Siphonochilus aethiopicus, Xerophyta retinervis and Zantedeschia aethiopica for their pharmacological properties against key bacteria; Staphylococcus aureus (ATCC 12600), Klebsiella pneumonia (ATCC 13883), Streptococcus pyogenes (ATCC 12344) and Haemophilus parainfluenzae (ATCC 7901) as well as the fungus Candida albicans (ATCC 10231) these microorganisms are known to cause chest infections. In the microdilution antibacterial assay, the crude extracts of the screened medicinal plants showed activity at minimal inhibitory concentrations (MICs) ranging from 0.098 to >12.5 mg/ml. In the disc-diffusion assay, only the ethanol extract of stems from Siphonochilus aethiopicus and water extract of leaves from Zantedeschia aethiopica showed zones of inhibition of 13.24 and 21.10 mm. All the other screened extracts showed no zones of inhibition, which may possibly indicate that plants were ineffective against Haemophilus parainfluenzae. One or more extracts from the tested plants were effective against one or both Gram-positive bacteria investigated in the study. There was no good antifungal activity shown in the study as the MIC and minimal fungicidal concentrations (MFCs) values were higher than 1 mg/ml. Genotoxicity of medicinal plant extracts that showed good antibacterial activity ≤ 0.5 mg/ml was evaluated using the Salmonella microsome assay without S9 metabolic activation. Two strains of Salmonella TA98 and TA102 were used in the Ames test. Most tested extracts were non-mutagenic in the Ames test except for the Siphonochilus aethiopicus roots which showed a dose dependent increase. The ethanolic crude extracts were screened in an immunological assay to determine the level of competitive binding to the receptors for the treatment of asthma and related conditions. Histamine is intimately associated with allergies. Datura stramonium flowers and fruits experienced remarkable histamine binding of approximately 97% at both concentrations (400 and 800 μg/ml). The immunological activity may be attributed to the various phytochemical constituents in the crude extracts. Ballota africana leaves and stems, Datura stramonium flowers and fruits, roots and stems as well as Zantedeschia aethiopica leaves showed excellent affinity with histamine ranging between 88 and 97% and these medicinal plants could potentially serve as a new effective antihistamine when compared to the currently available pharmaceuticals. Most of the medicinal plants tested may potentially provide remedies for asthma and related conditions such as eczema, rhinitis (hayfever), anaphylaxis, sinusitis, chronic obstructive pulmonary disease (COPD), emphysema, bronchiectasis and bronchitis.