Microbial And Heavy Metal Contaminations In Selected Herbal Medicinal Products Sold In Nairobi, Kenya

Abstract

Background: The use of traditional herbal medicinal products has been increasing worldwide due to the readily available raw materials and low cost compared to the synthetic industrial preparations. Medicinal herbs have been reported to be contaminated with agents and microorganisms indigenous to the soil and plants where they are grown. Confounded with poor unhygienic and handling pactices, the microbial safety and quality of these products is a public health concern. Broad objective: The study aimed at determining microbial and heavy metals contamination in selected herbal medicinal products sold in Nairobi, Kenya. Methodology: The study employed an exploratory as well as laboratory based experimental design. The herbal products were purchased from the markets, and transported to the Kenya Medical Research Institute laboratory for processing. Microbial contamination was determined using standard procedures and compared with European pharmacopoeia specifications. The levels of infestation were expressed as colony forming units. Antibiotic resistant genes were determined using polymerase chain reactions. Screening of the presence of mycotoxins was done using Envirologix Quick toxin kits. Heavy metal analysis was determined using Atomic Absorption Spectroscopy. Data was coded and analysed using SPSS and Excel computer packages. Pearson chi square test and Fisher excert test was used to determine associations between variables at 95% confidence interval (p ≤ 0.05). Results and Discussion: The study sampled 138 herbal products from different market outlets. The sampled herbal products were in capsules, liquid, juice, cream/lotion, powder, and syrup formulations. Bacterial contaminated samples were 117(84.8%) while 61(44.2%) were contaminated with fungi. Products from street vendors, herbal clinics which were in powder and liquid forms had cfu/g beyond the European pharmacopeia accepted limits [bacteria <1.0x103cfu/g (47.6%) and fungi <104/105cfu/g (1.6%)]. About 15.2% of the samples had fumonisins levels beyond the accepted limits while 5.2% had aflatoxins levels beyond these limits (4ppb). These samples were from street vendors and herbal clinics, which were in powder and liquid formulations. There was no significant association between the presence of fungi and aflatoxins/fumonisin contamination in the herbal products (2 test; p>0.05). The maximum permissible level of copper, zinc and iron were within accepted permissible limits. However, the nickel levels among some herbal products were beyond (35ppm) the recommended limits. Bacillus, Klebsiella, Proteus, Staphylococcus, Streptomyces, Escherichia, Enterobacter, Serratia, Yersinia, Morganella, Citrobacter, Erwinia xvii and Shigella were the bacterial genera identified. While Aspergillus, Penicillium, Rhizomucor, Rhodotorula, Absidia, Alternaria and Fusarium are among the fungal genera identified in this study. Some [35(36.5%)] bacteria isolates were resistant to one or more antibiotic tested. The phenotypic drug resistant bacteria were positive for drug resistance genes. The sources of contaminations could be soils and dust since most herbal products are prepared from roots and stem barks that are already in contact with the soil/dust. Fungi which inhabits the soil produce mycotoxins has secondary metabolites hence explaining the fumonisins and aflatoxins detection in the herbal products. Hawkers and street vendors packaged their products in bottles and plastic containers previously used for other products hence could make the product susceptible to microbial or chemical contamination due to inadequate cleaning. Handling of herbal products by street vendors could expose them to contaminations because some are not properly packaged. Those sold in the herbal clinics and supermarkets could have been contaminated during processing and handling. Conclusion and Recommendation: From this study, it is evident that some herbal medicinal products sold in Nairobi are highly contaminated with potential microbial pathogens including fungal toxins. Herbalist should be trained on how to apply good manufacturing practices, good harvesting practices and the safe handling and storage of herbal medicinal products. The study therefore recommends that policies be enacted to enable regulation of herbal medicinal products sold in the Kenyan market for public health reasons.