Biofilm battles: confronting stubborn resistance in dental healthcare by harnessing the antimicrobial potential of South African medicinal plants

An in vitro investigation of indigenous South African medicinal plants used to treat oral infections

Goats are an integral part of the livelihoods of South Africans, particularly in the rural communities, yet reproductive inefficiencies (low libido, poor semen quality, uterine infections, postpartum disorders, parasitism, and nutrition gaps) limit their productivity. Most resource challenged farmers resort to the use of ethnoveterinary plants for reproductive health of their goats due to their safety and ease of access; however, there is still a lack of standardization on their safety, dosing and efficacy. This study aimed to review and document the South African traditional medicinal plants used to enhance reproductive performance in goats. The study carried out a narrative review of ethnoveterinary surveys and pharmaco-ethnobotanical literature focused on South Africa, complemented by relevant goat reproduction studies. Our search used various keywords, including "medicinal plants," "goat breeding," "ethnoveterinary," and "medicinal plants" to identify relevant literature in several databases, including Scopus, Web of Science, Access to Global Online Research in Agriculture, and ScienceDirect. Additional searches were conducted using citations found in articles in these databases. The focus was on peer reviewed journals published between the year 2000 and 2025 on South African medicinal plants used to enhance goat reproduction, whether directly or indirectly. During the literature review, it was found that among other plants Securidaca longepedunculata Fresen. (violet tree), Moringa oleifera Lam (moringa), Elephantorrhiza elephantina (Burch.) Skeels (elephant root), Kigelia africana (Lam.) Benth. (sausage tree), Aloe ferox Mill., were frequently mentioned. Strong evidence was noted from ethnobotanical use to in vitro/in vivo validation, though limited but growing, especially for anthelmintic and antioxidant actions. Based on the literature, it can be concluded that South Africa's ethnobotanical resources hold credible value for improving goat reproduction by acting as antioxidants, regulating hormones, fighting infections, and controlling parasites that affect body condition. However, well-designed goat studies with proper dosing and safety testing are limited.

Endophytes are bacteria or fungi which live inside the host plant and participate in many biological processes without causing disease or other adverse effects. Endophytes are recognised as a rich source of secondary metabolites with potentially useful pharmacological properties. Many South African medicinal plants are highly under-investigated sources of potentially useful endophytic microbes. In this report six endophytic fungi were obtained from the leaves, stems and roots of South African medicinal plants which are known for their traditional uses and pharmacological properties. The endophytic fungi were isolated from Cotyledon orbiculata L., Psychotria zombamontana (Kuntze) Petit, Tecomaria capensis (Thunb.) Lindl., Catha edulis (Vahl) Endl. and Melianthus comosus Vahl. The crude extracts of the isolated endophytic fungi were investigated for their antimicrobial potential, extracellular enzymatic activity and phosphate solubilization. Additionally, the present study used genetic screening to assess the ability of the endophytic fungi to synthesize bioactive compounds, indicated by the presence of the polyketide synthase type 1 (PKS 1) gene. In preliminary microbial inhibition screening the fungal extracts had promising antifungal activity against Cryptococcus neoformans and Candida albicans. Furthermore, the endophytic fungus Talaromyces funiculosus displayed extracellular enzymatic activity, namely xylanase and cellulase. Five fungal strains demonstrated ability to solubilize phosphate and three strains demonstrated the presence of polyketide synthase type 1 (PKS 1) gene. It is worth considering further investigation of their bioactive secondary metabolites.

Studies on anthelmintic activity of medicinal plants have received insufficient interest and attention from researchers despite the high incidence of helminth infections in the poorer communities of South Africa. There are only a few anthelmintic remedies available which are inadequate in terms of accessibility, affordability and probably efficacy. In this review, we reappraised the various anthelmintic studies on South African medicinal plants to highlight how much and/or how little is known. The rich botanical and medicinal plant knowledge in South Africa is an indication of the potential of discovering potent treatments against helminth diseases in both humans and livestock. A total of 115 plant species encompassing 43 families screened for their anthelmintic potential (mainly nematodes) are listed in the current review. Combretaceae and Fabaceae were the most commonly used families. Tetradenia riparia, Hypoxis colchicifolia, Apodytes dimiata and Leucosidea sericea are a few examples of the South African species that have demonstrated promising anthelmintic activity. Even though other species such as Dicerocaryum eriocarpum, Berchemia zeyheri and Acorus calamus are potent anthelmintics, caution must be exercised in administering these plant extracts because of their potential toxic effects. Besides the benefit of validating the efficacy of traditional medicines, compounds from South African medicinal plants could also provide a template for novel synthetic anthelmintics. However, the major bottleneck in exploring more South African medicinal plants for anthelmintic properties is probably the lack of a robust, rapid and reliable screening technique as well as adequate funding schemes. Perhaps, there could be more success stories via increased research outputs with the development and availability of high throughput screening methods for assessing the activity of these medicinal plants as well as their resultant bioactive compounds. In addition, accessibility of funds to acquire latest technology and motivate researchers will inevitably stimulate more studies geared toward alleviating the problems posed by helminth infections.

Microbial biofilm and quorum sensing are two intertwined traits that have been used by microorganisms for their survival and improved virulence. They have been implicated as the cause of severe infections in humans as their incidence makes it difficult to treat common infections and the possibility of recurrent infections is high. Microbial biofilm and quorum sensing have also been increasingly implicated in the food processing and the medical industry where they have caused food and surface contamination. As a result of emerging resistance, conventional control methods are fast becoming ineffective. In this review, we highlight the potential of South African plants as sources of antibiofilm and quorum quenching bioactive secondary metabolites. The review emphasizes antimicrobial studies of medicinal plants with regard to foodborne pathogens and the relevant public health importance. Also discussed is the role of quorum sensing and biofilm formation in antimicrobial resistance. A total of 46 plant species belonging to 27 families and 31 isolated bioactive compounds were documented to have antibiofilm and quorum quenching capacity against foodborne pathogens. This review seeks to summarize present knowledge on South African medicinal plants with antibiofilm and quorum quenching potential. It also provides support for continuing investigations on South African medicinal plants with previously reported good to excellent antimicrobial activities.

A review of the traditional use of southern African medicinal plants for the treatment of malaria

South Africa has a long history and strong belief in traditional herbal medicines. Using ethnobotanical knowledge as a lead, a large number of South African medicinal plants have been discovered to possess a wide spectrum of pharmacological properties. In this review, bioprospecting of endophytes is highlighted by following the advantages of the ethnomedicinal approach together with identifying unique medicinal plants where biological activity may be due to endophytes. This review focuses on the current status of South African medicinal plants to motivate the research community to harness the benefits of ethnobotanical knowledge to investigate the presence of endophytic microbes from the most potent South African medicinal plants. The potential chemical diversity and subsequent putative medicinal value of endophytes is deserving of further research. A timely and comprehensive review of literature on recently isolated endophytes and their metabolites was conducted. Worldwide literature from the last 2 years demonstrating the importance of ethnobotanical knowledge as a useful approach to discover endophytic microbes was documented. Information was obtained from scientific databases such as Pubmed, Scopus, Scirus, Google Scholar, Dictionary of Natural Products, Chemical s Services, official websites, and scientific databases on ethnomedicines. Primary sources such as books, reports, dissertations, and thesises were accessed where available. Recently published information on isolated endophytes with promising bioactivity and their bioactive natural products worldwide (2015-2017) was summarized. The potential value of South African medicinal plants as sources of endophytes is discussed. The insights provided through this study indicate that medicinal plants in South Africa are highly under-investigated sources of potentially useful endophytic microbes. New approaches may be used by medicinal plant scientists for further exploration of natural products from endophytic fungi and bacteria in southern Africa.

Background: Pseudomonas aeruginosa is amongst the three high-ranking pathogens on the World Health Organization’s global priority list of antibiotic-resistant bacteria. The list highlights research priorities in drug discovery and development.Aim: This study aimed to provide a detailed account of efforts by researchers to find anti-P. aeruginosa compounds from South African medicinal plant species during the period 2000–2020.Method: Various online research and journal databases were used to obtain information relating to South African medicinal plants and P. aeruginosa.Results: During the study period (2000–2020), only 31 studies reported on the antibacterial properties of South African medicinal plants against the pathogen. Given that P. aeruginosa is a serious cause of morbidity and mortality worldwide, it was interesting to note that none of the published reports were dedicated solely to the pathogen. Furthermore, only one study included the antibiotic-resistant mutants of the pathogen as a test organism. Over 150 plant species belonging to 78 families were screened against the bacterium. Barringtonia racemosa, Croton megalobotrys, Erythrina caffra, Leucosidea sericea, Maesa lanceolata, Morella serrata and Trichilia emetica exhibited potent anti-P. aeruginosa properties (minimum inhibitory concentration [MIC] ˂ 0.1 mg/mL). Plumbagin, a compound isolated from the leaves of Aristea ecklonii demonstrated promising activities (MIC = 0.008 mg/mL) against the bacterium. Essential oils extracted from some plants demonstrated noteworthy antibacterial synergistic effects (fractional inhibitory concentration index [FICI] ˂ 0.5) when used in pairwise combinations with conventional antibiotics.Conclusion: Overall, empirical evidence presented in the scantly available literature suggests that novel anti-P. aeruginosa agents could be developed from South African herbal extracts.

Antifungal, anti-oxidant activity and cytotoxicity of South African medicinal plants against mycotoxigenic fungi

As the use of medicinal plants continues to gain popularity worldwide, there is dire need for herbal medicines to be guaranteed in their safety and efficacy. South Africa has a largely under-explored medical flora scientifically due to the vast number of plant species that are consumed for medicinal purposes by the public, creating an urgent need to better define plants with therapeutic effects. To meet these aims, a combination of high-throughput analytical techniques that are sensitive and versatile are used for the standardization and authentication of commercialized natural products as part of quality control regimes. These methods also serve to highlight the role of analytical methods in providing accurate and reliable information pertaining to the biochemicals of medicinal plants in those species whose chemistry remains partially understood or poorly characterized. The review highlights the advancements made in analytical technology for the assessment of biochemical profiles, biomarker compounds and quality control in chosen commercialized products, produced from indigenous South African species. We also summarize studies on the phytochemistry, pharmacology, clinical trials and available patents associated with some of South Africa’s medicinal plants where commercialization has occurred or is imminent. This was achieved through a detailed literature search using web-based database searches including Google Scholar, Scopus and Web of Science (WoS) as well as ethnobotanical literature on South African medicinal plants. Bibliometric analysis was performed on the data mined from WoS. It is clear that future advancements and further development of the natural products industry in South Africa will benefit from a diverse range of technological approaches.

BackgroundOxidative stress predisposes the human and animal body to diseases like cancer, diabetes, arthritis, rheumatoid arthritis, atherosclerosis and chronic inflammatory disorders. Hence, this study seeks to determine the antioxidant, anti-inflammatory and anti-arthritic activities of acetone leaf extracts of nine South African medicinal plants that have been used traditionally to treat arthritis and inflammation.MethodsThe anti-inflammatory activity of the extracts was determined by investigating inhibition of nitric oxide production in lipopolysaccharide activated RAW 264.7 macrophages as well as 15-lipoxygenase enzyme inhibition. An anti-protein denaturation assay was used to determine the anti-arthritic properties of the extracts. The antioxidant activity was determined using the 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2′-azino-bis (3-ethyl-benzthiazoline-6-sulfonic acid) (ABTS) radical scavenging assays and ferric reducing antioxidant power (FRAP). The total phenolic and total flavonoid concentration of extracts were determined by using standard methods.ResultsAll extracts inhibited nitric oxide production in a dose-dependent manner in the LPS-stimulated RAW 264.7 macrophages. Extracts of Maesa lanceolata and Heteromorpha arborescens inhibited NO production by 99.16 % and 89.48 % at a concentration of 30 μg/ml respectively. Elaeodendron croceum and Calpurnia aurea extracts had strong activity against 15-lipoxygenase activity with IC50 values of 26.23 and 34.70 μg/ml respectively. Morus mesozygia and Heteromorpha arborescens extracts had good in vitro anti-arthritic activity with IC50 values of 11.89 and 53.78 μg/ml, the positive control diclofenac sodium had IC50 value of 32.37 μg/ml. The free radical scavenging activity of the extracts in DPPH assays ranged between 7.72 and 154.77 μg/ml. Trolox equivalent antioxidant capacity (TEAC) and FRAP values ranged from 0.06 to 1.32 and 0.06 to 0.99 respectively.ConclusionsResults from this study support the traditional use of the selected medicinal plants in the management of arthritis and other inflammatory conditions. The free radical scavenging capacity of the extracts may be related to an immune boosting potential.

A review on traditionally used South African medicinal plants, their secondary metabolites and their potential development into anticancer agents

There has been a steady rise in antibiotic resistance of bacteria and this urgently calls for the discovery of alternative therapeutic agents. Honey possesses therapeutic potentials which includes antimicrobial activity. Although the antimicrobial activity of honey has been effectively established against an extensive spectrum of microorganisms, it differs depending on the type of honey. To date, not much extensive studies of the antibacterial properties of South African honeys on enteric microorganisms have been conducted. The objective of this study was to compare the antibacterial activity of extracts of six different honeys with those of medical plants commonly used in South Africa. Using a broth dilution method, the antibacterial activity extracts of six South African honeys and medicinal plants against six enteric microorganisms viz- Enterobacter cloacae, Escheriachia coli, Klebsiella pneumoniae, Citrobacter freundii isolated from geophagia samples and Aeromonas hydrophila and plesiomonas isolated both from stool and water samples using agar well diffusion method was done. Different concentrations of honey and plant extracts were tested against each type of microorganism. Briefly, two-fold dilutions of honey solutions were tested to determine the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against each type of microorganism. Extracts from both South African honeys and medicinal plants showed zones of inhibition that ranged from 6.94 to 37.94 mm. The most susceptible bacteria were Escheriachia coli, Aeromonas hydrophila and Plesiomonas shigelloides . MIC and MBC values of extracts were found in the range of 0.625 to 5.000 mg/ml. Extracts of honey showed good antibacterial activity against most organisms than the standard antibiotics such as Ampicillin and Gentamycin. Honey extracts showed antibacterial activity against most microorganisms which were showing some degree of resistance to commercial antibiotics. Extracts from South African honeys and medicinal plants exhibited variable activities against different microorganisms. This result suggests that the honeys could potentially be used as an alternative therapeutic agent against certain microorganisms. Keywords: Agar well diffusion assay, honey, minimum inhibitory concentration, minimum bactericidal concentration African Journal of Biotechnology , Vol. 13(4), pp. 616-625, 22 January, 2014

Fungal infections are still most prevalent in the South African population. Fungal respiratory infections and diseases are the cause of severe clinical challenges and mortality in patients with compromised immune systems. Clinical signs of coronavirus disease of 2019 (COVID-19) such as lung injury, hyperglycemia due to diabetes, host iron and zinc depletion, hypoxia, immunosuppression, steroid therapy, and long-term hospitalization predispose patients to opportunistic fungal infections. Fungal pathogens, including Cryptococcus, Aspergillus, and Candida species, cause coinfections in patients infected with (COVID-19), and this has a negative impact on the patients’ pharmacological management goals. Cryptococcus, Aspergillus, and Candida species cause respiratory infections and illnesses including pneumonia, pulmonary aspergillosis, pulmonary candidiasis, and pulmonary cryptococcosis. South African traditional medicinal plants have been used in the treatment of respiratory symptoms and diseases caused by these fungal pathogens. Medicinal plants contain secondary metabolites possessing antifungal activity against Cryptococcus, Aspergillus, and Candida species. Moreover, medicinal plants are cheaper and easily accessible and are believed to be safe. This review documents the use of South African traditional medicinal plants including Artemisia absinthium, Artemisia afra, Dicoma anomala, Felicia species, Mentha species, Ruta graveolens, and Seasia erosa in the treatment of fungal infections and diseases caused by these pathogens.

Potential antiparkinsonian agents derived from South African medicinal plants