A comparison of the antimicrobial activity and toxicity of six combretum and two terminalia species from southern Africa

Fractionation and Antibacterial Evaluation of the Surface Compounds from the Leaves of Combretum zeyheri on Selected Pathogenic Bacteria

Combretum zeyheri is traditionally used for the treatment of many infections, including bacterial infections. The aim of this study was to fractionate and evaluate antibacterial activity of the crude extract of C. zeyheri, as well as the surface compounds from the leaves of C. zeyheri, in two pathogenic bacteria, Staphylococcus aureus and Pseudomonas aeruginosa. The antibacterial activities of fractions obtained from chromatographic separations were determined using broth microdilution assay on the laboratory and clinical strains of S. aureus and P. aeruginosa. The fractionation of the compounds on the leaf surface yielded 262 fractions. The fractionated compounds with similar TLC profiles were pooled together to yield 47 pools. The extract and pooled fractions CZSC151154, CZSC155160, and CZSC209213 showed significant antibacterial activity with MIC values ranging from 12.5 μg/ml to 100 μg/ml. The clinical strain of S. aureus had MIC greater than 100 μg/ml for CZSC151154 and CZSC155160. The minimum bactericidal concentration values for these fractions were also in the range of 12.5 μg/ml to 100 μg/ml. The extract and fractions CZSC151154, CZSC155160, and CZSC209213 showed a concentration-dependent inhibition of growth in S. aureus. Analyses of the CZSC209213 pool by LC-MS showed the presence of nine compounds which are (3R,7R)-1,3,7-octanetriol, (-)-tortuosamine, 11-aminoundecanoic acid, 1-piperidinecarboxaldehyde, 3-hydroxy-4-isopropylbenzyl alcohol 3-glucoside, hydroxy-isocaproic acid, oleamide, palmitic amide, phytospingosine, and sphinganine. In conclusion, C. zeyheri leaf surface compounds exhibited antibacterial activity. The crude extract and the pooled fractions showed concentration-dependent inhibition of growth on S. aureus. Results from this study indicate the potential of C. zeyheri as a source of lead compounds that may be further developed into antibacterial drugs.

Antioxidant and Antibacterial Activities of the Leaf and Stem Extracts of Combretum molle (R. Br. ex G. Don.) Engl. & Diels

Medicinal plants offer reasonable and accessible alternatives to synthetic drugs and are often devoid of the adverse side effects, toxicity, and pathogenic resistance associated with synthetic medicine. Combretum molle has been utilized in African traditional medicinal practices and purportedly contains bioactive compounds with medicinally beneficial effects. This study investigated the hexane, chloroform, and methanol leaf and stem extracts for their antioxidant properties using the 2,2'-diphenyl-1-picrylhydrazyl radical scavenging and ferric-reducing antioxidant power assays. The study additionally analyzed the methanol extracts for their antibacterial activity against Gram-negative Escherichia coli (ATCC 25922) and Gram-positive Staphylococcus aureus (ATCC 25923) bacteria using agar well diffusion. Relative to the scavenging activity of the ascorbic acid control (79.15 ± 0.63% at 15 µg/mL to 94.61 ± 0.12% at 240 µg/mL), the plant's radical scavenging activities were exceptionally high in the methanolic leaf and stem extracts (p < 0.05), ranging from 94.58 ± 1.10% at 15 µg/mL to 99.22 ± 0.30% at 240 µg/mL and 91.57 ± 1.71% at 15 µg/mL to 99.60 ± 0.20% at 240 µg/mL, respectively, suggesting a strong capacity to donate hydrogen ions. High scavenging activities were additionally observed in the chloroform stem (78.68 ± 1.18% at 15 µg/mL to 98.14 ± 1.22% at 240 µg/mL) and hexane leaf (72.12 ± 4.38% at 15 µg/mL to 89.87 ± 1.50% at 240 µg/mL) extracts (p < 0.05). All extracts exhibited poor ferric-reducing abilities in relation to the gallic acid control (100 ± 0.00%) at all concentrations (p < 0.05). The leaf and stem extracts exhibited broad-spectrum antibiotic capabilities against both tested strains, with significant activity at higher concentrations (p < 0.05). Overall, both the leaf and stem extracts of C. molle exhibited similar antioxidant and antibacterial activities. These findings warrant further pharmacological research on C. molle for potential drug development.

Insights into the Microbicidal, Antibiofilm, Antioxidant and Toxicity Profile of New O-Aryl-Carbamoyl-Oxymino-Fluorene Derivatives

The unprecedented increase in microbial resistance rates to all current drugs raises an acute need for the design of more effective antimicrobial strategies. Moreover, the importance of oxidative stress due to chronic inflammation in infections with resistant bacteria represents a key factor for the development of new antibacterial agents with potential antioxidant effects. Thus, the purpose of this study was to bioevaluate new O-aryl-carbamoyl-oxymino-fluorene derivatives for their potential use against infectious diseases. With this aim, their antimicrobial effect was evaluated using quantitative assays (minimum inhibitory/bactericidal/biofilms inhibitory concentrations) (MIC/MBC/MBIC), the obtained values being 0.156-10/0.312-10/0.009-1.25 mg/mL), while some of the involved mechanisms (i.e., membrane depolarization) were investigated by flow cytometry. The antioxidant activity was evaluated by studying the scavenger capacity of DPPH and ABTS•+ radicals and the toxicity was tested in vitro on three cell lines and in vivo on the crustacean Artemia franciscana Kellog. The four compounds derived from 9H-fluoren-9-one oxime proved to exhibit promising antimicrobial features and particularly, a significant antibiofilm activity. The presence of chlorine induced an electron-withdrawing effect, favoring the anti-Staphylococcus aureus and that of the methyl group exhibited a +I effect of enhancing the anti-Candida albicans activity. The IC50 values calculated in the two toxicity assays revealed similar values and the potential of these compounds to inhibit the proliferation of tumoral cells. Taken together, all these data demonstrate the potential of the tested compounds to be further used for the development of novel antimicrobial and anticancer agents.

Ethnopharmacology, Antimicrobial Potency, and Phytochemistry of African Combretum and Pteleopsis Species (Combretaceae): A Review

Bacterial and fungal resistance to antibiotics is of growing global concern. Plants such as the African Combretum and Pteleopsis species, which are used in traditional medicine for the treatment of infections, could be good sources for antimicrobial extracts, drug scaffolds, and/or antibiotic adjuvants. In African countries, plant species are often used in combinations as traditional remedies. It is suggested that the plant species enhance the effects of each other in these combination treatments. Thus, the multi-species-containing herbal medications could have a good antimicrobial potency. In addition, plant extracts and compounds are known to potentiate the effects of antibiotics. The objective of this review is to compile the information on the botany, ethnopharmacology, ethnobotany, and appearance in herbal markets of African species of the genera Combretum and Pteleopsis. With this ethnobotanical information as a background, this review summarizes the information on the phytochemistry and antimicrobial potency of the extracts and their active compounds, as well as their combination effects with conventional antibiotics. The databases used for the literature search were Scopus, Elsevier, EBSCOhost, PubMed, Google Scholar, and SciFinder. In summary, a number of Combretum and Pteleopsis species were reported to display significant in vitro antibacterial and antifungal efficacy. Tannins, terpenes, flavonoids, stilbenes, and alkaloids-some of them with good antimicrobial potential-are known from species of the genera Combretum and Pteleopsis. Among the most potent antimicrobial compounds are arjunglucoside I (MIC 1.9 µg/mL) and imberbic acid (MIC 1.56 µg/mL), found in both genera and in some Combretum species, respectively. The in vitro antimicrobial properties of the extracts and compounds of many Combretum and Pteleopsis species support their traditional medicinal uses.

Bioautography-guided HPTLC-MS as a rapid hyphenated technique for the identification of antimicrobial compounds from selected South African Combretaceae species

INTRODUCTION

Many species within Combretaceae are traditionally used for the treatment of bacterial infections. The similarity in chemistry and antimicrobial activities within the family pose a challenge in selecting suitable species for herbal drug development.

OBJECTIVE

This study aimed at rapidly identifying antimicrobial compounds using bioautography-guided high-performance thin-layer chromatography coupled with mass spectrometry (HPTLC-MS).

METHODS

Hierarchical cluster analysis of ultra-performance liquid chromatography-mass spectrometry data from the methanol extracts of 77 samples, representing four genera within Combretaceae, was carried out. Based on groupings on the dendrogram, 15 samples were selected for bioautography analysis against four pathogens (Staphylococcus aureus, Bacillus cereus, Escherichia coli and Salmonella typhimurium). Active compounds were identified using HPTLC-MS analysis of bands corresponding to the inhibition zones.

RESULTS

Bioautography revealed 15 inhibition zones against the four pathogens, with the most prominent present for Combretum imberbe. Analysis of the active bands, using HPTLC-MS indicated that flavonoids, triterpenoids and combretastatin B5 contributed to the antibacterial activity. The compounds corresponding to molecular ions m/z 471 (Combretum imberbe) and 499 (Combretum elaeagnoides) inhibited all four pathogens, and were identified as imberbic acid and jessic acid, respectively. Chemotaxonomic analysis indicated that arjunic acid, ursolic acid and an unidentified triterpenoid (m/z 471) were ubiquitous in the Combretaceae species and could be responsible for their antibacterial activities.

CONCLUSION

Application of HPTLC-MS enabled the rapid screening of extracts to identify active compounds within taxonomically related species. This approach allows for greater efficiency in the natural product research workflow to identify bioactive compounds in crude extracts.

Ethnobotanical Study of Medicinal Plants Used for Management of Cancer in Karonga District, Northern Malawi

BACKGROUND

In Malawi, cancer is one of the leading causes of morbidity and mortality. This has led to increased use of herbal medicines for cancer management.

OBJECTIVE

This study aimed at identifying medicinal plants that are used for the management of cancer in the southern area of Karonga district, Northern Malawi.

METHODS

Semi-structured individual questionnaire interviews were used to collect ethnobotanical data from traditional herbal practitioners in the study area.

RESULTS

A total of twenty-six (26) plant species from seventeen (17) botanical families were reported by Traditional Herbal Practitioners to be effective in the management of cancer. The botanical families with the representation of more than one plant species were Fabaceae with five species, followed by Combretaceae and Anacardiaceae with tree species each and Meliaceaewith two species. The relative frequency of citation (RFC) showed that Senna singueana (RFC = 0.833), Lannea discolour (RFC = 0.833), Melia azedarach (RFC = 0.667), and Moringa oleifera (RFC = 0.667) were the medicinal plant species that were frequently mentioned and used in the study. The recipes could be a mixture of plant species or plant parts such as the leaves, barks, roots, rhizomes, seeds, flowers, and fruits.

CONCLUSION

The study showed that a potential cancer management drug could be developed from the medicinal plant species found in the area. The results of this study could provide baseline information on medicinal plant species for further phytochemical studies and other studies to validate their use.

Antibacterial Activity and Time-kill Assay of Terminalia catappa L. and Nigella sativa L. against Selected Human Pathogenic Bacteria

The current investigation aims to test the susceptibility of human pathogenic clinical isolates and MTCC strains to leaf and seed extracts of Terminalia catappa and Nigella sativa. Disc diffusion assay, micro dilution assay and minimum Bactericidal Concentration investigated the susceptibility of bacteria to the test extracts. The active extract was subjected to phytochemical screening, separation of the phytochemicals by Thin Layer Chromatography, bioactivity guided assay and Time- kill assay. Acetone and methanol extracts of T.catappa revealed, significant inhibition of clinical origin Staphylococcus aureus followed by Proteus vulgaris and the MTCC strains Staphylococcus aureus, Salmonella typhi, Pseudomonas aeroginosa and Bacillus subtilis. Nigella sativa inhibited the growth of clinical origin Staph.aureus and MTCC strain of Staph.aureus, Salmonella typhi and B.subtilis. Minimum inhibitory concentration for all the test bacteria was reported in the range of 5000μg/ml to 9 μg/ml in T. catappa extract. Most sensitive being the clinical isolate Staph. aureus and Proteus vulgaris. The bactericidal concentration for the test bacteria was found to be between 5000μg/ml and 625μg/ml. Phyto-chemical analysis of leaf extracts of T. catappa found to have dominated by polyphenols (Terpenoids, steroids, flavonoids, flavones, saponins and tannins) and N.sativa extracts recorded the presence of alkaloids, proteins and oils and fats. TLC profiling of the acetone extract revealed many antibacterial active bands. Bands having Retention factor 0.47 and 0.52 were active against the test bacteria. Time kill assay of the acetone extract of T. catappa were carried out for the first time. The extract exhibited dose dependent bactericidal and bacteriostatic activity against the clinical isolates.

Formulation and Antibacterial Activity of Liquid Soap Containing Ketapang (Terminalia catappa L.) Leaves Extract

Ketapang (Terminalia catappa L.) is traditionally used by the community to treat infections of the skin caused by bacteria or fungi. In this study, T. catappa leaves extract was added to the liquid soap formula as an antibacterial. The purpose of this study was to determine the secondary metabolite compounds contained in T. catappa leaves extract, physical evaluation of the preparation, and antibacterial activity of liquid soap. Liquid soap formula is made with various concentrations of T. catappa leaves extract F0 (0%), F1 (1%), F2 (2%), and F3 (3%). The resulting soap was evaluated for organoleptic, pH, high foam, homogeneity, irritation, and its activity against Staphylococcus aureus, Staphylococcus epidermidis, and Escherichia coli using the disc diffusion method. The results showed that the T. catappa leaves extract contained flavonoids, tannins, saponins, and triterpenoids. The liquid soap formula F0 is clear, while F1, F2, and F3 have the characteristics of brown-dark brown, homogeneous, pH between 4.6-5.2, foam stability between 67-72%, which is not significantly different and stable after five minutes of testing, and it does not irritate the skin. Terminalia catappa leaves extracts liquid soap has antibacterial activity at a concentration of 1%, 2%, and 3%, with the largest inhibition zone diameter produced by S. aureus.

The traditional use of southern African medicinal plants for the treatment of bacterial respiratory diseases: A review of the ethnobotany and scientific evaluations

ETHNOPHARMACOLOGICAL RELEVANCE

Multiple plant species were used traditionally in southern Africa to treat bacterial respiratory diseases. This review summarises this usage and highlights plant species that are yet to be verified for these activities.

AIM OF THE STUDY

This manuscript reviews the traditional usage of southern African plant species to treat bacterial respiratory diseases with the aim of highlighting gaps in the literature and focusing future studies.

MATERIALS AND METHODS

An extensive review of ethnobotanical books, reviews and primary scientific studies was undertaken to identify southern African plants which are used in traditional southern African medicine to treat bacterial respiratory diseases. We also searched for southern African plants whose inhibitory activity against bacterial respiratory pathogens has been conmfirmed, to highlight gaps in the literature and focus future studies.

RESULTS

One hundred and eighty-seven southern African plant species are recorded as traditional therapies for bacterial respiratory infections. Scientific evaluations of 178 plant species were recorded, although only 42 of these were selected for screening on the basis of their ethnobotanical uses. Therefore, the potential of 146 species used teraditionally to treat bacterial respiratory diseases are yet to be verified.

CONCLUSIONS

The inhibitory properties of southern African medicinal plants against bacterial respiratory pathogens is relatively poorly explored and the antibacterial activity of most plant species remains to be verified.

Metabolite profiling, arginase inhibition and vasorelaxant activity of Cornus mas, Sorbus aucuparia and Viburnum opulus fruit extracts

The present study investigated the effects of Cornus mas, Sorbus aucuparia and Viburnum opulus fruit extracts on arginase activity and arterial vasodilation. V. opulus fruit extract exerted the highest vasorelaxant activity in phenylephrine precontracted rat aortic rings (EC₅₀ = 6.31 ± 1.61 μg/mL) and a significant inhibition of arginase (IC₅₀ = 71.02 ± 3.06 μg/mL). By contrast, S. aucuparia and C. mas fruit extracts showed no important anti-arginase activity and a significantly weaker activity in the rat aortic rings relaxation assay (EC₅₀ = 100.9 ± 11.63 and 78.52 ± 8.59 μg/mL, respectively). For all extracts, the main mechanism of vasodilation was proven to be endothelium-dependent. HPLC-ESI-Q-TOF-MS/MS studies revealed a very complex metabolite profiling in all three extracts with chlorogenic acid accounting for 30.89, 0.72 and 2.03 mg/g in V. opulus, C. mas and S. aucuparia fruit extracts, respectively. All extracts were declared non-toxic in the brine shrimp acute toxicity test. Our study highlights potential benefits of V. opulus fruit extract in diseases associated with endothelial dysfunction and impaired vasodilation.

Endophytic Fungi from Terminalia Species: A Comprehensive Review

Endophytic fungi have proven their usefulness for drug discovery, as suggested by the structural complexity and chemical diversity of their secondary metabolites. The diversity and biological activities of endophytic fungi from the Terminalia species have been reported. Therefore, we set out to discuss the influence of seasons, locations, and even the plant species on the diversity of endophytic fungi, as well as their biological activities and secondary metabolites isolated from potent strains. Our investigation reveals that among the 200-250 Terminalia species reported, only thirteen species have been studied so far for their endophytic fungi content. Overall, more than 47 fungi genera have been reported from the Terminalia species, and metabolites produced by some of these fungi exhibited diverse biological activities including antimicrobial, antioxidant, antimalarial, anti-inflammatory, anti-hypercholesterolemic, anticancer, and biocontrol varieties. Moreover, more than 40 compounds with eighteen newly described secondary metabolites were reported; among these, metabolites are the well-known anticancer drugs, a group that includes taxol, antioxidant compounds, isopestacin, and pestacin. This summary of data illustrates the considerable diversity and biological potential of fungal endophytes of the Terminalia species and gives insight into important findings while paving the way for future investigations.

Antimicrobial natural product research: A review from a South African perspective for the years 2009-2016

ETHNOPHARMACOLOGICAL RELEVANCE

This review provides information on the antimicrobial research which has taken place on South African natural products for the last eight years (2009-2016). This important field is the backbone of all studies involving the use of medicinal plants against infectious diseases and hence can form the mainstay for future studies.

MATERIALS AND METHODS

All publications within the years 2009-2016 were considered. Exclusion criteria were studies not involving South African medicinal natural products and those publications where full articles could not be accessed. An overview of the most common experimental methods used and new advances in terms of antimicrobial investigations are provided. Disease categories selected for further investigation were skin and wounds, respiratory, gastrointestinal, sexually transmitted and ophthalmic infections amongst others. Alternate natural products and combinations studies were also included.

RESULTS

The minimum inhibitory concentration (MIC) was the most commonly used experimental method to determine antimicrobial activity. Staphylococcus aureus was the most commonly tested skin pathogen and Klebsiella pneumoniae was the most common pathogen implicated in respiratory disorders. Only 20% of gastrointestinal studies included commonly implicated pathogens such as Shigella flexneri and Campylobacter species.

CONCLUSION

Multidisciplinary studies have emerged as a strong support for antimicrobial investigations and show the importance of including toxicity when studying antimicrobial efficacy. Alternate approaches (for example biofilms and quorum sensing) at examining antimicrobial effects are encouraged. Studies on resistant strains require more insight and future recommendations should look at consistent dosing and investigations on compound interactions amongst others.