Microbial, phytochemical, toxicity analyses and antibacterial activity against multidrug resistant bacteria of some traditional remedies sold in Buea Southwest Cameroon

Microbial Contamination of Herbal Medicines in Africa, 2000-2024: A Systematic Review

Introduction

Herbal medicine has been a cornerstone of healthcare for centuries, with an estimated 80% of the world's population relying on it. In Africa, herbal medicine is the backbone of rural healthcare, serving 80% to 90% of the population. Despite its widespread use, the safety of herbal medicine raises a significant concern considering the lack of regulation and testing, particularly in Africa. Microbial contamination is a primary safety risk threatening consumer health. In this systematic review, we aimed to synthesise evidence on microbial contamination in herbal medicines across Africa, provide a clear understanding of the problem, and inform effective public health interventions regarding microbial contamination of herbal medicines in Africa.

Method

The systematic review was conducted in accordance with the PRISMA guidelines. A literature search was conducted across PubMed, Web of Science, Science Direct, Scopus, and Google Scholar using appropriate search terms. Eligible studies were selected based on predetermined criteria, and data were extracted and analysed.

Results

The review included fifty eligible studies in Africa, with a combined sample size of 1996, of which 1791 showed microbial contamination. Bacterial contaminants were reported in 98% of studies, with Escherichia coli (62%) being the most reported bacteria, followed by Staphylococcus aureus (57%), and Bacillus spp. (55%). Fungal contaminants were reported in 70% of studies, with Aspergillus spp. (40%) being the most reported, followed by Penicillium spp. (27%) and Candida spp. (26%). Parasitic contaminants were reported in 2% of the studies reviewed. A total of 70 bacterial species, 37 fungal species, and 6 parasite species were identified in this review.

Conclusion

Herbal medicines in Africa pose significant health threats to consumers due to the high prevalence of diverse microbial contaminants and clinically significant pathogens. This emphasises the need for stricter regulations and quality control measures in the production, sale and use of herbal medicines.

Contamination of herbal medicinal products in low-and-middle-income countries: A systematic review

The use of herbal medicinal products (HMPs) has grown significantly across low-and-middle-income countries (LMICs). Consequently, the safety of these products due to contamination is a significant public health concern. This systematic review aimed to determine the prevalence, types, and levels of contaminants in HMPs from LMICs. A search was performed in seven online databases, i.e., Africa journal online (AJOL), Cumulative Index to Nursing and Allied Health Literature (CINAHL), Directory of Open Access Journals (DOAJ), Health Inter-Network Access to Research Initiative (HINARI), World Health Organization Global Index Medicus (WHO GIM), Scopus, and PubMed using appropriate search queries and reported as per the "Preferred Reporting Items for Systematic Reviews and Meta-Analyses" (PRISMA) guidelines. Ninety-one peer-reviewed articles published from 1982 to 2021 from 28 different countries across four continents were included in the study. Although metals, microbial, mycotoxins, pesticides, and residual solvents were the reported contaminants in the 91 articles, metals (56.0%, 51/91), microbial (27.5%, 25/91), and mycotoxins (18.7%, 17/91) were the most predominant. About 16.4% (1236/7518) of the samples had their contaminant levels above the regulatory limits. Samples tested for microbial contaminants had the highest proportion (46.4%, 482/1039) of contaminants exceeding the regulatory limit, followed by mycotoxins (25.8%, 109/423) and metals (14.3%, 591/4128). The proportion of samples that had their average non-essential metal contaminant levels above the regulatory limit was (57.6%, 377/655), 18.3% (88/480), 10.7% (24/225), and 11.3% (29/257) for Pb, Cd, Hg, and As, respectively. The commonest bacteria species found were Escherichia coli (52.3%, 10/19) and Salmonella species (42.1%, 8/19). This review reported that almost 90% of Candida albicans and more than 80% of moulds exceeded the required regulatory limits. HMP consumption poses profound health implications to consumers and patients. Therefore, designing and/or implementing policies that effectively regulate HMPs to minimize the health hazards related to their consumption while improving the quality of life of persons living in LMICs are urgently needed.

Antiplasmodial Properties of Aqueous and Ethanolic Extracts of Ten Herbal Traditional Recipes Used in Thailand against Plasmodium falciparum

This study evaluated the in vitro and in vivo antiplasmodial efficacy and toxicity of aqueous and ethanolic extracts from traditional recipes used in Thailand. The aqueous and ethanolic extracts of ten traditional recipes were tested for in vitro antiplasmodial activity (parasite lactate dehydrogenase assay), cytotoxicity (MTT assay), and hemolysis). Oxidant levels were measured using cell-permeable probe 5-(and-6)-chloromethyl-2',7'-dichlorodihydrofluorescein diacetate fluorescent dye-based assays. The best candidate was chosen for testing in mouse models using 4-day suppressive and acute toxicity assays. An in vitro study showed that ethanolic extracts and three aqueous extracts exhibited antiplasmodial activity, with an IC₅₀ in the range of 2.8-15.5 µg/mL. All extracts showed high CC₅₀ values, except for ethanolic extracts from Benjakul, Benjalotiga, and Trikatuk in HepG2 and Benjalotiga and aqueous extract from Chan-tang-ha in a Vero cell. Based on the results of the in vitro antiplasmodial activity, an aqueous extract of Triphala was chosen for testing in mouse models. The aqueous extract of Triphala exhibited good antiplasmodial activity, was safe at an oral dose of 2 g/kg, and is a potential candidate as a new source for the development of antimalarial drugs.

Medically important bacteria isolated from commercial herbal medicines in Kampala city indicate the need to enhance safety frameworks

The high global bacterial infection burden has created need to investigate the neglected potential drivers of pathogenic bacteria, to inform disease prevention. Kampala is facing a proliferation of herbalists, selling herbal medicine (HM), of largely unregulated microbiological quality. We evaluated the bacterial contamination burden in HM sold in Kampala, to support evidence-based redress. The total viable loads (TVL), total coliform counts (TCC), E. coli counts, and prevalence of selected bacterial strains in 140 HM were examined using conventional culture, following the guidelines of World Health Organization (WHO), and Uganda National Drug Authority (NDA). Data were analyzed using D'Agostino-Pearson test, frequencies, proportions, Chi-square, and Mann-Whitney U test with STATA version-15.0. Fifty (35.7%), fifty-nine (42.1%), and twelve (8.6%) HM were unsafe for human use because they exceeded WHO's permissible limits for TVL, TCC, and E. coli counts respectively. Solids had significantly higher mean TVL than liquids. Violation of NDA's guidelines was significantly associated with high TVL. Fifty-nine bacteria, viz., Klebsiella pneumoniae (n = 34; 57.6%), Escherichia. coli (12; 20.3%), Staphylococcus aureus (7; 11.9%), Klebsiella oxytoca (3; 5.1%), Bacillus cereus, Pseudomonas aeruginosa, and Enterobacter spp. (1; 1.7% each), were isolated from 45 (32.1%) samples. These bacteria can cause severe clinical diseases, and promote deterioration of HM potency.

In Vitro Antibacterial Potential against Multidrug-Resistant Salmonella, Cytotoxicity, and Acute Biochemical Effects in Mice of Annona muricata Leaf Extracts

The treatment of Salmonella infections is threatened by multidrug resistance necessitating the search for alternative treatments, such as from medicinal plants. There are several reports on the antibacterial activity of Annona muricata. This study assessed the activity against multidrug-resistant (MDR) Salmonella and also the toxicity of the leaves of this plant. The hexane and methanol extracts of the leaves were screened against characterized MDR isolates by disc diffusion and microdilution methods. A cytotoxicity test was performed on monkey kidney epithelial cells; an acute toxicity test was conducted in BALB/c mice and the liver and kidney functions were assessed at the end of the test. Both extracts recorded weak activity in the disc test. Conversely, the extracts showed a wide range of activity against specific Salmonella isolates in the microdilution assay, and the lowest minimum inhibitory concentration value recorded was 0.0625 mg/mL. The hexane extract (ANO_HEX) was not cytotoxic (CC₅₀ = 57.7 µg/mL) and was also not toxic to the mice at 2000 mg/Kg bodyweight, while the methanol extract (ANO_MET) was cytotoxic (CC₅₀ = 18.44 µg/mL), and mortality was recorded at 2000 mg/Kg but not at 300 mg/Kg. There were no significant changes in biomarkers of the liver (alanine aminotransferase and aspartate aminotransferase) and kidney (creatinine and urea) functions (P > 0.05), except for ANO_HEX which significantly decreased creatinine (P = 0.01), in the test mice which was not considered a toxic effect. In conclusion, this study has demonstrated high bacteriostatic activity against MDR Salmonella and a low risk of toxicity of A. muricata leaves. Hence, the leaves are a potential alternative treatment for resistant Salmonella infection. The natural products should be further investigated in vitro and in vivo.

Antibiotic-resistance in medically important bacteria isolated from commercial herbal medicines in Africa from 2000 to 2021: a systematic review and meta-analysis

Background

Antimicrobial resistance is swiftly increasing all over the world. In Africa, it manifests more in pathogenic bacteria in form of antibiotic resistance (ABR). On this continent, bacterial contamination of commonly used herbal medicine (HM) is on the increase, but information about antimicrobial resistance in these contaminants is limited due to fragmented studies. Here, we analyzed research that characterized ABR in pathogenic bacteria isolated from HM in Africa since 2000; to generate a comprehensive understanding of the drug-resistant bacterial contamination burden in this region.

Methods

The study was conducted according to standards of the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA). We searched for articles from 12 databases. These were: PubMed, Science Direct, Scifinder scholar, Google scholar, HerbMed, Medline, EMBASE, Cochrane Library, International Pharmaceutical Abstracts, Commonwealth Agricultural Bureau Abstracts, African Journal Online, and Biological Abstracts. Prevalence and ABR traits of bacterial isolates, Cochran’s Q test, and the I² statistic for heterogeneity were evaluated using MedCalcs software. A random-effects model was used to determine the pooled prevalence of ABR traits. The potential sources of heterogeneity were examined through sensitivity analysis, subgroup analysis, and meta-regression at a 95% level of significance.

Findings

Eighteen studies met our inclusion criteria. The pooled prevalence of bacterial resistance to at least one conventional drug was 86.51% (95% CI = 61.247–99.357%). The studies were highly heterogeneous (I² = 99.17%; p < 0.0001), with no evidence of publication bias. The most prevalent multidrug-resistant species was Escherichia coli (24.0%). The most highly resisted drug was Ceftazidime with a pooled prevalence of 95.10% (95% CI = 78.51–99.87%), while the drug-class was 3^rd generation cephalosporins; 91.64% (95% CI = 78.64–96.73%). None of the eligible studies tested isolates for Carbapenem resistance. Extended Spectrum β-lactamase genes were detected in 89 (37.2%) isolates, mostly Salmonella spp., Proteus vulgaris, and K. pneumonia. Resistance plasmids were found in 6 (5.8%) isolates; the heaviest plasmid weighed 23,130 Kilobases, and Proteus vulgaris harbored the majority (n = 5; 83.3%).

Conclusions

Herbal medicines in Africa harbor bacterial contaminants which are highly resistant to conventional medicines. This points to a potential treatment failure when these contaminants are involved in diseases causation. More research on this subject is recommended, to fill the evidence gaps and support the formation of collaborative quality control mechanisms for the herbal medicine industry in Africa.

Macrofilaricidal Activity, Acute and Biochemical Effects of Three Lichen Species Found on Mount Cameroon

Onchocerciasis is a parasitic infection affecting a relatively small population globally but has very devastating pathological outcomes. Ivermectin and recently moxidectin are the only drugs approved for clinical management of the disease, both of which have several limitations. In particular, they are efficacious against microfilariae (microfilaricidal) with no activity against adult worms (nonmacrofilaricidal). Promising anthelmintic activity has been reported in some lichens. This study investigated three lichens, Usnea articulata, Parmotrema tinctorum, and Heterodermia obscurata, found on Mount Cameroon, for potential macrofilaricidal activity. Organic extracts were screened for anti-Onchocerca activity against Onchocerca ochengi isolated from cattle skin using worm motility and MTT formazan assays. Toxicity of highly active extracts was investigated on monkey kidney epithelial (LLCMK2) cells and in BALB/c mice (2000 mg/kg body weight) including effects on liver enzymes. The methanol extract of P. tinctorum (Pam_met) was the most active against adult male worms (IC₅₀ = 8.1 μg/mL) with the highest selectivity index (SI = 21.3). U. articulata was the most active against the adult female (IC₅₀ = 36.3 μg/mL) but had a low SI value (3.4). No mortality and no adverse effects were recorded in the acute toxicity test. These two most active extracts had no significant effect on liver enzymes, alanine aminotransferase, and aspartate (P values < 0.05), but a high AST : ALT ratio (2.59) for Pam_met indicates likely reversible adverse hepatic toxicity. The high macrofilaricidal activity and selectivity of P. tinctorum suggest it is a potential source of new macrofilaricides which should be further investigated to identify its bioactive constituents.

Herbal medicine used for the treatment of diarrhea and cough in Kampala city, Uganda

BACKGROUND

Globally, diarrheal and respiratory diseases are among the main causes of mortality and morbidity. In Uganda, cities are facing proliferation of trade in herbal medicines (HM), including those for diarrhea and/or cough. Information on the economic, and the ethnopharmacological aspects of these HM is scarce, deterring the sector from achieving optimal capacity to support national development. We profiled the anti-diarrhea and/or anti-cough HM, and the basic economic aspects of HM trade in Kampala city, to support ethnopharmacological knowledge conservation and strategic planning.

METHODS

A cross-sectional survey was conducted on 65 herbalists using semi-structured questionnaires. This was supplemented by an observational survey using a high-resolution digital camera. Data were collected following the guidelines for research on HM, established by Uganda National Drug Authority, and World Health organization.

RESULTS

Eighty-four plant species from 41 families were documented. Fabaceae and Myricaceae had the highest number of species (9, 10.7% each). Citrus limon (L.) Osbeck was the most commonly cited for cough, with a relative frequency of citation (RFC) of 1.00, and its relative medical importance was not significantly different from the other top 5 species except for Azadirachta indica A.Juss (RFC = 0.87). Entada abyssinica A. Rich (RFC = 0.97) was the most cited for diarrhea. Trees (34, 40.5%) were mostly used, and mainly harvested from wild habitats (55.2%) in 20 districts across Uganda. These HM were mainly sold as powders and concoctions, in markets, shops, pharmacies, and roadside or mobile stalls. The highest prices were Uganda Shillings (UGX) 48,000 ($13.15)/kg for Allium sativum L, and UGX 16,000 ($4.38)/kg for C. limon. All participants used HM trade as a sole source of basic needs; majority (60.0%) earned net monthly profit of UGX. 730,000 ($200) ≤ 1,460,000 ($400). The main hindrances to HM trade were the; disruptions caused by the COVID-19 pandemic (n = 65, 100%), and the scarcity of medicinal plants (58, 89.2%).

CONCLUSION

There is a rich diversity of medicinal plant species traded in Kampala to treat diarrhea and cough. The HM trade significantly contributes to the livelihoods of the traders in Kampala, as well as the different actors along the HM value chain throughout the country.

Evaluation of macrofilaricidal and microfilaricidal activities against Onchocerca ochengi and cytotoxicity of some synthesized azo compounds containing thiophene backbone

Control and treatment of onchocerciasis, a devastating tropical filarial disease caused by Onchocerca volvulus, rely solely on the community directed treatment with ivermectin. However, ivermectin is only microfilaricidal with evidence of resistance of the parasite among other limitations, which necessitate the search for new efficacious and safe filaricides. Ten synthetic thienylazoryl dyes were screened in vitro against adult and microfilariae worm stages of Onchocerca ochengi based on worm motility and MTT formazan assay. Cytotoxicity of active compounds was assessed on monkey kidney epithelial cells (LLC-MK2) using the MTT formazan assay. Seven (7) compounds showed both macrofilaricidal activity against adult male worms and microfilaricidal activity among which three 4a, 4c and 4e recorded the highest activity (IC₅₀ = 4.2 to 8.8μM) against adult male worms, comparable to some standard anthelmintics. Five compounds showed rapid activity against microfilariae with 100% inhibition after 24-h incubation. The active compounds were nontoxic on monkey kidney cells (CC₅₀> 4μg/mL), but their selectivity index values were relatively low (≤ 3). The thienylazoaryls with both macrofilaricidal and microfilaricidal activities may yield molecules which could be used for eradication of onchocerciasis following further medicinal chemistry modification of their structures to enhance their selectivity.