Antimicrobial and cytotoxicity properties of the organic solvent fractions of Clerodendrum myricoides (Hochst.) R. Br. ex Vatke: Kenyan traditional medicinal plant

A Systematic Review of Medicinal Plants of Kenya used in the Management of Bacterial Infections

Kenya’s vision 2030 partly aims at ensuring adequate health care for all, and the integration of traditional healthcare practices into the national healthcare system would present a more rapid alternative towards the realization of universal health coverage in Kenya. Currently, research on Kenyan medicinal plants with potential antibacterial activity remains vastly fragmented across numerous literature studies and databases; thus, it is imperative to collate and appraise these data for the ease of future research and possible clinical application. Objective. This review aims at exploring and compiling research evidence on medicinal plants used in the management of bacterial infections in Kenya, with a focus on their efficacy and safety. Methodology. A comprehensive web-based systematic review using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines was executed to highlight the Kenyan medicinal plants used for the management of bacterial infections in Kenya. This review includes studies published until January 2021 from the PubMed, Science Direct, AJOL, and Google Scholar databases. Results. A total of 105 Kenyan medicinal plants belonging to 43 families have their in vitro activity against various human pathogenic bacteria evaluated. Plants from the Lamiaceae, Rutaceae, and Fabaceae families were the most commonly studied. Aloe secundiflora, Toddalia asiatica, Senna didymobotrya, Warbugia ugandensis, Tithonia diversifolia, Fuerstia africana, Olea africana, and Harrisonia abyssinica were the plants frequently evaluated within Kenya. The plants with the strongest antimicrobial activities were Toddalia asiatica, Hagenia abyssinica, Ocimum gratissimum, Harrisonia abyssinica, Senna didymobotrya, Olea Africana, Camellia sinensis, and Tarmarindus indica. Conclusion. Based on a published work, it is evident that traditional medicine is seemingly an acceptable and efficient system among Kenyan communities in the management of bacterial infections. Kenya’s rich biodiversity with diverse secondary metabolites presents a promising source of new therapeutic alternatives with possibly different mechanisms of action against bacteria.

Antiviral iridoid glycosides from Clerodendrum myricoides

The methanol root extract of Clerodendrum myricoides (Hochst.) Vatke afforded two new (1, 2) and two known (3, 4) iridoid glycosides. The structures of the isolated compounds were established based on NMR, IR, UV and MS data analyses. The crude extract and the isolated constituents were assayed for antiviral activity against the human respiratory syncytial virus (RSV) in human laryngeal epidermoid carcinoma (HEp-2) cells. The crude extract inhibited RSV infectivity at EC₅₀ = 0.21 μg/ml, while it showed cytotoxicity against HEp-2 cells with CC₅₀ = 9 μg/ml. Compound 2 showed 43.2% virus inhibition at 100 μM, while compounds 1 as well as 3 and 4 had only weak antiviral and cytotoxic activities.

The Botanical, Chemical and Ethnobotanical Diversity of Southern African Lamiaceae

The Lamiaceae is undoubtedly an important plant family, having a rich history of use that spans the globe with many species being used in folk medicine and modern industries alike. Their ability to produce aromatic volatile oils has made them valuable sources of materials in the cosmetic, culinary, and pharmaceutical industries. A thorough account of the taxonomic diversity, chemistry and ethnobotany is lacking for southern African Lamiaceae, which feature some of the region’s most notable medicinal and edible plant species. We provide a comprehensive insight into the Lamiaceae flora of southern Africa, comprising 297 species in 42 genera, 105 of which are endemic to the subcontinent. We further explore the medicinal and traditional uses, where all genera with documented uses are covered for the region. A broad review of the chemistry of southern African Lamiaceae is presented, noting that only 101 species (34%) have been investigated chemically (either their volatile oils or phytochemical characterization of secondary metabolites), thus presenting many and varied opportunities for further studies. The main aim of our study was therefore to present an up-to-date account of the botany, chemistry and traditional uses of the family in southern Africa, and to identify obvious knowledge gaps.

Antimicrobial activity, phytochemical characterization and gas chromatography-mass spectrometry analysis of Aspilia pluriseta Schweinf. extracts

Aspilia pluriseta is associated with various bioactivities, although with limited scientific justification. In this study, we evaluated the antimicrobial activity, and characterized the phytochemicals of root extracts of A. pluriseta aimed at validating its therapeutic potential. We used BACTEC MGIT™ 960 system to test for antitubercular activity, disc-diffusion together with the microdilution method to evaluate antimicrobial activities and qualitative phytochemical tests together with gas chromatography-mass spectrometry (GC-MS) analysis to determine the phytochemicals that associated with A. pluriseta extracts activity. We show that methanolic crude extract (at 1 g/mL) had high Mycobacterium tuberculosis (MTB) inhibitory activity (0 growth unit) and considerable potency against Escherichia coli (11.7 mm), Staphylococcus aureus (9.0 mm), and Candida albicans (7.7 mm). All the extract fractions exerted remarkable antimycobacterial activities with minimum inhibitory activity of between 6.26 – 25 μg/mL. The highest antimicrobial activity of petroleum ether and dichloromethane fraction was against E. coli at inhibition zone diameters of 8.3 mm, and 8.0 mm, respectively, while ethyl acetate fraction was against S. aureus with an inhibition zone of 8.7 mm. Methanolic fraction exhibited broad-spectrum activity against 87.5% of the tested microbes (inhibition zones 6.3–8.3 mm). Furthermore, we qualitatively detected terpenoids, alkaloids, and phenolics such as flavonoids, and anthraquinones in extract fractions. GC-MS analysis detected an abundance of fatty acid esters, 2-hydroxy-1-(hydroxymethyl) ethyl ester-hexadecanoic acid, and 2,3-dihydroxy propyl ester-octadecanoic acid and four alkanes. Taken together, we show that A. pluriseta extract fractions (especially ethyl acetate and methanolic fractions) have strong selective antitubercular activity, and thus, we scientifically validate the use of A. pluriseta as a potential source for the discovery of novel antitubercular agents.

Total alkaloids of Sophora alopecuroides- and matrine-induced reactive oxygen species impair biofilm formation of Staphylococcus epidermidis and increase bacterial susceptibility to ciprofloxacin

Objective

To investigate the mechanism by which total alkaloids of Sophora alopecuroides (TASA) and matrine (MT) impair biofilm to increase the susceptibility of Staphylococcus epidermidis (S. epidermidis) to ciprofloxacin.

Methods

The minimum biofilm inhibitory concentration (mBIC) was determined using a 2-fold dilution method. Structure of biofilm of S. epidermidis was examined by Confocal Laser Scanning Microscope (CLSM). The cellular reactive oxygen species (ROS) was determined using a DCFH-DA assay. The key factors related to the regulation of ROS were accessed using respective kits.

Results

TASA and MT were more beneficial to impair biofilm of S. epidermidis than ciprofloxacin (CIP) (P < 0.05). TASA and MT were not easily developed resistance to biofilm-producing S. epidermidis. The mBIC of CIP decreased by 2–6-fold following the treatment of sub-biofilm inhibitory concentration (sub-BIC) TASA and MT, whereas the mBIC of CIP increased by 2-fold following a treatment of sub-BIC CIP from the first to sixth generations. TASA and MT can improve the production of ROS in biofilm-producing S. epidermidis. The ROS content was decreased 23%−33% following the treatment of sub-mBIC CIP, whereas ROS content increased 7%−24% following treatment with TASA + CIP and MT + CIP combination from the first to sixth generations. Nitric oxide (NO) as a ROS, which was consistent with the previously confirmed relationship between ROS and drug resistance. Related regulatory factors-superoxide dismutase (SOD) and glutathione peroxidase (GSH) could synergistically maintain the redox balance in vivo.

Conclusion

TASA and MT enhanced reactive oxygen species to restore the susceptibility of S. epidermidis to ciprofloxacin.

Medicinal plants used in managing diseases of the respiratory system among the Luo community: an appraisal of Kisumu East Sub-County, Kenya

BACKGROUND

Poor access to healthcare in rural communities causes many people to seek herbalists who use medicinal plants for the treatment of various disease conditions. Most knowledge of traditional herbal medicine makes use of indigenous remedies which are often undocumented and are at risk of being lost. The preservation of this knowledge may facilitate scientific inquiry into promising new therapeutic molecules.

METHODS

Semi-structured questionnaires were used to collect the sociodemographic information of 30 herbalists in Kisumu East Sub County. The local names of medicinal plants used in managing illnesses of the respiratory system, their habit, active parts, indications, methods of preparation, routes of administration, scientific identity, and conservation status were also recorded. Other reported traditional uses, pharmacological activities, and toxicological data were identified via a literature search.

RESULTS

Most herbalists were female (86.7%), aged between 61 and 70 years (43.3%) with no formal education (56.7%), and had 21-30 years of practice (30%). 44 plant species, belonging to 43 genera and 28 families were identified. Leguminosae and Rutaceae plant families were predominant, leaves were frequently used (33%), and trees were the most common habit (44.4%). Most plants were collected in the wild (79.2%), preparation was mainly by decoction (68.8%), and the administration was mainly orally. The main indication was cough and 79.5% of all documented plant species had previously been reported to have a pharmacological activity relevant to the mitigation of respiratory illnesses. Toxicological data was available for 84.1% of the plant species identified.

CONCLUSIONS

The predominant use of roots, root barks, and root tubers by herbalists in Kisumu East Sub County threatens to negatively impact the ecological survival of some plant species. The preservation of herbalists' knowledge of medicinal plants in the study area is a pressing concern considering their advanced age and little formal education. There is a need to conserve some of the medicinal plants documented in this study. The medicinal claims made by herbalists also warrant scientific scrutiny.

Potential Role of Plant Extracts and Phytochemicals Against Foodborne Pathogens

Foodborne diseases are one of the major causes of morbidity and mortality, especially in low-income countries with poor sanitation and inadequate healthcare facilities. The foremost bacterial pathogens responsible for global outbreaks include Salmonella species, Campylobacter jejuni, Escherichia coli, Shigella sp., Vibrio, Listeria monocytogenes and Clostridium botulinum. Among the viral and parasitic pathogens, norovirus, hepatitis A virus, Giardia lamblia, Trichinella spiralis, Toxoplasma and Entamoeba histolytica are commonly associated with foodborne diseases. The toxins produced by Staphylococcus aureus, Bacillus cereus and Clostridium perfringens also cause these infections. The currently available therapies for these infections are associated with various limited efficacy, high cost and side-effects. There is an urgent need for effective alternative therapies for the prevention and treatment of foodborne diseases. Several plant extracts and phytochemicals were found to be highly effective to control the growth of these pathogens causing foodborne infections in in vitro systems. The present review attempts to provide comprehensive scientific information on major foodborne pathogens and the potential role of phytochemicals in the prevention and treatment of these infections. Further detailed studies are necessary to evaluate the activities of these extracts and phytochemicals along with their mechanism of action using in vivo models.

Antiquorum sensing, antibiofilm formation and cytotoxicity activity of commonly used medicinal plants by inhabitants of Borabu sub-county, Nyamira County, Kenya

Productions of various bacterial traits like production of virulence factors (e.g. toxins, enzymes), biofilm formation, luminescence among others, have been known to be controlled by quorum sensing (QS), a process that is dependent on chemical signals or autoinducers (AIs). Bacteria known to rely on such AIs are known to be virulent and tend to be resistant against various antimicrobial agents. Therefore, strategies aimed at the inhibition of QS pathways, are regarded as potential novel therapies in managing bacterial virulence hence reducing their ability to induce infections in humans. In the present study, a portfolio of 25 medicinal plant extracts (ethanol 50% v/v) used in southwestern Kenya were assayed against a transformed E. coli Top 10 reporter QS strain. This biosensor responds to the exogenous addition of 3-oxo-N-hexanoyl homoserine lactone (3OC₆HSL) expressing green fluorescent protein (GFP). The large majority of the screened medicinal plants seemed to exhibit toxic effects and almost none of them induced antiquorum sensing (AQS) activity. This could be the consequence of the presence of mixed compounds in the extracts. Elaeodendron buchananii Loes and Acacia gerrardii Benth extracts that seemed to show AQS activity were further proved found to possess mild AQS but with defined antimicrobial activities, and no antibiofilm formation inhibition. As a control, an E. coli pBCA9145_jtk2828::sfGFP strain that produces constitutively GFP was used and confirmed that none of the two extracts quenched the fluorescence of sfGFP. Cytotoxicity assays with mammalian MDCK cells also did indicate that the selected extracts with putative AQS activity, also reduced the cell viability. Therefore, further studies will be needed to separate and re-test the individual compounds especially from the selected two promising plants.