Ethnopharmacological and Toxicological Study of Medicinal Plants Used Against Respiratory Infections in Kisumu East Sub- County

Abstract

Respiratory diseases are a major cause of mortality in developing countries. Poor access to healthcare in rural areas makes many people in such communities to rely on traditional medicine. The current study was designed to address the following objectives: identify medicinal plants used to manage respiratory diseases in Kisumu East Sub-County, analyze the phytochemical composition of the plant extracts, establish the in- vitro antimicrobial activity of the crude extracts and evaluate in-vitro cytotoxicity of crude plants extracts against Artemia salina Leach (Artemiidae) larvae. An ethnobotanical survey was conducted in Kisumu East Sub -County. Semi- structured questionnaires were used to collect information from 30 Traditional Medicine Practitioners (TMPs). Sociodemographic characteristics of informants, local names of plants used, habit, active parts, indications, method of preparation, routes of administration, scientific identity and conservation status were recorded. A literature search was conducted via PubMed, Google Scholar, and Research Gate to identify reported activities of the plants. Three plants parts namely, the root of Acanthus polystachius Delile (Acanthaceae), the root bark of Keetia gueinzii (Sond.) Bridson (Rubiaceae) and the root tuber of Rhynchosia elegans A. Rich. (Leguminosae) were collected using standard methodologies. The parts were extracted using double distilled water, 100% acetone, and 100% methanol. The aqueous, acetonic and methanolic crude extracts were subjected to secondary phytochemical screening; antimicrobial activity against Staphylococcus aureus (S. aureus), Bacillus cereus (B. cereus), Escherichia coli (E. coli), and Candida albicans (C. albicans); and cytotoxic potential using the brine shrimp lethality assay. Standard methods were adopted for efficacy, safety evaluation and for identification of secondary metabolites in the test crude extracts. Majority of the TMPs were female and comprised of 26 practitioners (86.7%). From the survey, 45 plant species, belonging to 43 genera and 28 families were identified. Leguminosae and Rutaceae were the most dominant plant families. Leaves were mentioned by 19 respondents (32.8%), hence were the most commonly used, while trees were mentioned by 20 respondents (44.4%) and comprised the commonest habitat. A literature search established that at least 43/45 plant species had reported pharmacological activities. Qualitative phytochemical analysis of aqueous extracts of Keetia gueinzii showed presence of flavonoids, glycosides, phenols, saponins and tannins. Aqueous extracts of Acanthus polystachius contained saponins, phenols and tannins. Results from the antimicrobial evaluation showed the extracts had varying degrees of activity against the tested microorganisms. Aqueous and acetonic root bark extracts of Keetia gueinzii had the lowest Minimum Inhibitory Concentration (MIC) of 12.5 mg/ml against Staphylococcus aureus. The methanolic extract of Keetia gueinzii had the lowest MIC value of 100 mg/ml against Candida albicans. Brine lethality results showed that aqueous, acetonic and methanolic extracts of Rhynchosia elegans A. Rich. were toxic with LC50 values of 422.09 μg/ml, 175.77 μg/ml and 168.76 μg/ml respectively. Acetonic and methanolic extracts of Acanthus polystachius were also toxic with a LC50 value of 195.17 μg/ml and 174.26 μg/ml respectively. All extracts of Keetia gueinzii were non- toxic. This serves as the first report on the phytochemical composition, antimicrobial and cytotoxic activity of Acanthus polystachius, Keetia gueinzii and Rhynchosia elegans. With the exception of the root barks of Keetia gueinzii, the use of all other plants tested are limited by safety concerns. In their current crude form, these plants are not recommended for the management of microbial infections. However, the root bark of Keetia gueinzii warrants further research