Evaluation of anthelmintic, antiamoebic and antibacterial activity in traditional South African medicinal plants.

Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 2001.Traditional medicine in southern Africa draws upon a vast selection of plants to treat gastrointestinal disorders such as diarrhoea and intestinal parasites. The evaluation of these plants for biological activity is necessary, both to substantiate the use of these plants by healers, and also a possible lead for new drugs or herbal preparations. After a survey of the existing ethnobotanical literature, plants used to treat stomach ailments such as diarrhoea, dysentery or intestinal worm infestations were selected and submitted to bioassays according to their traditional uses. Extracts of the chosen plants were made using the solvents hexane, ethanol and water, to ensure the extraction of compounds with a wide range of polarity. In total, 138 extracts were tested for antibacterial activity, 72 for anthelmintic activity, and 42 for antiamoebic activity. Antibacterial activity was evaluated using the disc-diffusion assay, and Minimal Inhibitory Concentration (MIC) values were determined using a microdilution assay. The extracts were tested against the Gram-positive bacteria Bacillus subtilis and Staphylococcus aureus, and the Gram-negative bacteria Escherichia coli and Klebsiella pneumoniae. Ethanolic extracts showed the greatest activity and Gram-positive bacteria were the most susceptible microorganisms. The free-living nematode Caenorhabditis elegans, which is morphologically similar to parasitic nematodes, was used in two different assays to evaluate anthelmintic activity. A microdilution technique was employed to investigate antiamoebic activity against the enteropathogenic Entamoeba histolytica, the causal organism of amoebic dysentery. These assays were suitable for the screening of a large number of extracts at one time. Several plants exhibited significant activity against these test organisms. Many species of plants belonging to the family Combretaceae are used in southern African traditional medicine against a variety of ailments, including abdominal complaints, bilharzia and diarrhoea. Extracts of powdered leaf material of 24 species belonging to the Combretaceae were prepared using the solvents ethyl acetate, acetone, methanol and water. These extracts were screened for anthelmintic activity. Significant activity was exhibited by C. apiculatum, C. hereroense and C. mossambicense. The most anthelmintic activity was shown by acetone extracts, followed by ethyl acetate, water and then methanol extracts. The aromatic rhizomes of Acarus calamus L. are used extensively in traditional medicine worldwide. They reportedly relieve stomach cramps and dysentery, and are used as anthelmintics. Rhizome extracts of A. calamus growing in KwaZulu-Natal, South Africa, exhibited anthelmintic and antibacterial activity in the initial general screening. Using bioassay-guided fractionation, the phenylpropanoid β-asarone was isolated from the rhizome. This compound possessed both anthelmintic and antibacterial activity. It has previously been isolated from A. calamus, and a related species, A. gramineus. Different varieties of A. calamus exhibit different levels of β-asarone, with the diploid variety containing none of the compound. Mammalian toxicity and carcinogenicity of asarones has been demonstrated by other researchers, supporting the discouragement of the medicinal use of Acarus calamus by traditional healers in South Africa. Schotia brachypetala was another plant to show good antibacterial activity in the initial screening. The roots and bark of S. brachypetala are used in South African traditional medicine as a remedy for dysentery and diarrhoea. The lack of pharmacological and chemical data on this plant prompted a further investigation into its antibacterial activity. The differences in activity of ethanol and water extracts with respect to plant part, season and geographical position were analysed. No extreme fluctuations in activity were noted. Two other Schotia species, S. afra and S. capitata, were included in the study, and both displayed good antibacterial activity. The storage of the plant, either as dried, ground plant material at room temperature, or as an extract residue at -15°C, had little effect on the antibacterial activity. Preparing the extracts from fresh or dry material also did not notably affect the activity. In general, the ethanolic extracts were more active than the aqueous extracts. The chemical profiles on TLC chromatograms were compared and found to be very similar in the case of ethanol extracts prepared in different months of the year, and from different trees. The extracts of the three species, and of the leaves stored under various conditions, as well as extracts prepared from fresh or dry material, also showed similar TLC fingerprints. However, various plant parts of S. brachypetala showed distinctly different chemical compositions. The leaves of S. brachypetala showed slightly higher antibacterial activity than the roots. Fractionation of the ethanol extract of the dried leaves using liquid-liquid partitioning and chromatographic techniques yielded 9,12,15-octadecatrienoic (linolenic) acid and methyl-5, 11,14,17-eicosatetraenoate. These fatty acids displayed antibacterial activity against the Gram-positive bacteria Bacillus subtilis and Staphylococcus aureus, and activity to a lesser extent against the Gram-negative Escherichia coli and Klebsiella pneumoniae. Linolenic acid is known to have antibacterial activity. The screening of plants for biological activity yielded valuable preliminary information about the plants used by traditional healers to treat gastrointestinal illnesses. The isolation of biologically active compounds from two highly active plants was achieved

Pittosporum viridiflorum Sims (Pittosporaceae) : a review on a useful medicinal plant native to South Africa and tropical Africa

ETHNOPHARMACOLOGICAL RELEVANCE : Pittosporum viridiflorum Sims, a Pittosporaceae species, is used extensively in African traditional medicine (ATM) by various tribes. This review is an appraisal of the information concerning the description, distribution, conservation status, traditional uses, phytochemistry, pharmacology and toxicology of this species with the aim of reconciling it with its traditional use. MATERIALS AND METHODS : A wide-ranging literature search was conducted using database platforms such as Scopus, Google Scholar, Web of Science, ScienceDirect, PubMed and books including local reports and thesis submissions. RESULTS : Ten categories to which P. viridiflorum finds use in traditional medicine (TM) were found, and they include well-being, wounds, treatment of veterinary ailments, gastrointestinal and sexually transmitted diseases, kidney, circulatory and inflammatory disorders, as well as diseases such as cancer, tuberculosis, and malaria. Pharmacological tests conducted include those investigating antimicrobial, antidiarrhoeal, antimalarial, anticancer, anti-inflammatory, antioxidant and acaricidal properties. Promising activity was shown in a number of assays. Toxicological effects have also been reported from this species. However, it is recommended to conduct a detailed toxicological study, including genotoxicity, as this has not yet been evaluated. Compound(s) with antimalarial, anticancer and acaricidal properties have been isolated from P. viridiflorum. CONCLUSIONS : The collective pharmacological and phytochemical properties of P. viridiflorum gives credence to the use of this plant species against various diseases in ATM, thus steering significant interest towards in vivo studies and further research.The National Research Foundation (NRF), Pretoria, South Africa (NRF-Scarce Skills Post-doctoral Fellowship UID 96848 to BM and NRF Incentive Funding to LJM).http://www.elsevier.com/locate/jep2018-06-09hj2017Paraclinical Science

Bioprospecting of South African plants as a unique resource for bioactive endophytic microbes

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 endophyticmicrobes from the most potent South Africanmedicinal 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 Abstracts 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.The University of Pretoria, South Africahttp://www.frontiersin.org/Pharmacologyam2019Paraclinical Science

Bioprospecting of South African plants as a unique resource for bioactive endophytic microbes

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 endophyticmicrobes from the most potent South Africanmedicinal 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 Abstracts 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.The University of Pretoria, South Africahttp://www.frontiersin.org/Pharmacologyam2019Paraclinical Science

South African plants with nematicidal activity against root-knot nematodes : a review

Research on using plants as control agents for plant-parasitic nematodes has received substantial attention due to the ability of plant-derived extracts and compounds to either paralyze or kill nematodes. Nematicidal properties of certain plants have been tested in vitro and in vivo using glasshouse and field trials, either using powdered meal (plant material) or extracts by incorporating them as soil amendments or as seed treatments. The present review aims to document South African plants used for controlling root-knot nematodes, i.e. Meloidogyne spp., summarizing in vitro and in vivo results of experiments conducted to assess their efficacy. Several databases were mined to obtain information on plant use as organic amendments for controlling Meloidogyne infections in South Africa. Inclusion criteria focused on plants as organic amendments and the use of plants against Meloidogyne infection. Meloidogyne incognita race 1 and race 2 are the most commonly studied nematodes infecting tomatoes, which are highly susceptible to nematode infection. Seventeen plant species were reported to effectively reduce the population density of nematodes in the soil in glasshouse, microplot and field trials. The in vitro experiments are generally used as guides for investigating if activity occurs via mortality or egg hatchability. Further research exploring South African plants as control agents for root-knot nematodes, chemicals responsible for activity and the plants’ mode of action is warranted.The Agricultural Research Council Professional Development Programme (ARC-PDP), Health and Welfare Sector Education and Training Authority (HWSETA) and University of Pretoria Doctoral Support Bursary.http://www.elsevier.com/locate/sajbhj2021Paraclinical Science

Bioactive constituents from Malvastrum coromandelianum (L.) Garcke leaf extracts

Please read abstract in the article.The National Research Foundation (NRF) South Africa and a Visiting Professorship Fellowship 2018 at the Department of Paraclinical Sciences, Phytomedicine Programme, Faculty of Veterinary Sciences, University of Pretoria, South Africa.http://www.elsevier.com/locate/sajb2020-11-01hj2020Paraclinical Science

Tannin content of leaf extracts of 53 trees used traditionally to treat diarrhoea is an important criterion in selecting species for further work

AIM OF THE STUDY : In southern Africa many plant species are used to treat different ailments and diseases related to infections. Diarrhoea is not only an important disease of humans but also causes large losses in the animal production industry. The antimicrobial activity of many of these species may however, be based on their tannin content. Even though high tannin content may be therapeutically effective against pathogens causing diarrhoea, nutritional side effects limit its prophylactic use in animal production. The aims of the study were two-fold. In the first place it was to compile a list of species used traditionally to treat diarrhoea. The second aim was to identify and remove those species where a potential antidiarrhoeal activity may be due to tannins, because it would be counterproductive to use in production animal systems. MATERIALS AND METHODS : After a literature study, 53 tree species used to treat diarrhoea or dysentery in humans or animals in southern Africa were identified. Plant material was collected and dried powdered leaves were extracted with acetone. To select plants with potential use as prophylactics against diarrhoea, the tannin content was determined by a radial diffusion method of precipitation of bovine serum albumin in agar and expressed as gallic acid equivalents. RESULTS : Based on our literature research plant species from at least 37 tree families are used traditionally to treat diarrhoea in southern Africa. Most of the species were from the Fabaceae (9), Euphorbiaceae (6), Anacardiaceae (3) and Combretaceae (3). The highest tannin content of 11.3 mg/ml gallic acid equivalents was detected in leaf extracts of Combretummolle and Sclerocarya birrea. About 40% of the species tested contained no tannin based on the assay used. CONCLUSIONS : As other authors have found, the tannin content within a family varied strongly. Therefore it is dangerous to make any conclusions on the tannin content of the same plant family. About 42% of the species had no detectable tannin content and another 25% contained 0–2 mg/ml gallic acid equivalent tannins. In general it appears that inmost cases tannins do not play a major role in treating diarrhoea in southern African ethnomedicine. If aqueous extracts were used, the situation could have been different.The Medical Research Council and the Faculty of Veterinary Science, University of Pretoria, South Africa. Open Access funded by SAAB.http://www.elsevier.com/locate/sajbhb2017Paraclinical Science

Antibacterial and antibiofilm activity of selected medicinal plant leaf extracts against pathogens implicated in poultry diseases

Antimicrobial resistant poultry pathogens are responsible for treatment failure and economic losses, and can also be a source of resistant zoonotic infections representing a risk to human health. In 2006 the European Union banned the use of antibiotics as growth promoters in farm animals and other regions are likely to follow suit. Alternative products and strategies are sought to help maintain animal gut health to reduce the prevalence of pathogens in the food chain. The minimum inhibitory concentration (MIC) of organic and aqueous leaf extracts of Alchornea laxiflora, Ficus exasperata, Morinda lucida, Jatropha gossypiifolia, Ocimum gratissimum, and Acalypha wilkesiana were tested against bacterial poultry pathogens including Staphylococcus aureus, Enterococcus faecalis, Salmonella spp., Escherichia coli, Campylobacter spp., and fungal species (Aspergillus fumigatus, Aspergillus flavus, and Candida albicans) using a 2-fold serial microdilution method. Activity of extracts against biofilms of the pathogens was done using a modified crystal violet staining in vitro assay. The safety of extracts was determined against Vero and Caco-2 cells using a tetrazolium-based in vitro assay. Acetone and cold water extracts of M. lucida had the best activity against three bacteria (MIC = 0.05–0.07 mg/ml) and two fungal (MIC = 0.03–0.15 mg/ml) organisms, respectively. The E. coli isolate and A. flavus were the most susceptible bacteria and fungi, respectively. Caco-2 cells generally displayed higher selectivity index (SI) values compared to Vero cells and average SI values against Vero and Caco-2 cells for both bacteria and fungi ranged from 0.01 to 4.48 and 0.005 to 16.41, respectively. All plant extracts had good anti-biofilm activity (>50%) against at least one organism. The disruption of established biofilm growth by the plant samples proved to be more difficult to achieve than efficacy against planktonic forms of bacteria. This study shows that some of the plant species are potential candidates as alternative feed additives in poultry production. In the future, a poultry feed trial to evaluate their in vivo efficacy as herbal feed additives will be conducted.The National Research Foundation (NRF) of South Africa and the University of Pretoria.https://www.frontiersin.org/journals/veterinary-sciencedm2022Paraclinical Science

In vitro cytotoxicity and genotoxicity of five Ochna species (Ochnaceae) with excellent antibacterial activity

Extracts and fractions of some Ochna species had excellent antibacterial activity. Before considering the potential therapeutic use of these extracts it is important to determine the safety of extracts. The cytotoxicity of Ochna natalitia, Ochna pretoriensis, Ochna pulchra, Ochna gamostigmata, and Ochna serrulata (Ochnaceae) was determined in monkey kidney (Vero) cells, human hepatocellular carcinoma (C3A) cells and bovine dermis cells using the mitochondrial viability MTT assay. Their potential mutagenic effects were also determined using the Ames testwith strains Salmonella typhimuriumTA98 and TA100 with andwithoutmetabolic activation. The LC50 values (the lethal concentration at which 50% of the cells are killed) of the extracts on the various cell lines ranged from 26 to 99 μg/ml. None of the plant species was mutagenic (mutagenic index values ≤ 1.59 for TA98 and ≤0.92 for TA100). In a previous study, we determined the antibacterial activity of the five extracts against Staphylococcus aureus, Escherichia coli, Enterococcus faecalis and Pseudomonas aeruginosa. From this we calculated the selectivity index (SI) values by dividing the LC50 value by the minimum inhibitory concentration (MIC) to obtain the ratio of toxicity to bioactivity of each extract. The plant extracts had low SI values ≤ 1.307. This is a clear indication of non-selective toxicity, i.e. extracts are almost equally toxic to the bacteria and mammalian cell lines used in the assays. As a result, the extracts may have limited application as ingestible or intravenous therapeutic agents based on the in vitro findings. However, it may be necessary to also evaluate in vivo toxicity of the extracts in animal models as in vitro toxicity does not always equate to in vivo toxicity because of the difference in physiological microenvironment in live animals and tissue culture. Additionally, if it is the case that the toxic compounds are not the same as the active compounds, it may be possible to potentiate the extracts by the removal of toxic compounds and concentration of active compounds. The extracts may then be useful for development into treatments for topical bacterial infections.National Research Foundation of South Africa, the Medical Research Council and the University of Pretoria.http://www.elsevier.com/locate/sajbhb201