Lyndy Joy McGaw

The biological activity and chemistry of the southern African Combretaceae

AIM OF THE STUDY Members of the Combretaceae family are widely traded in the traditional medicine market in southern Africa. The family is also used for medicinal purposes in the rest of Africa and Asia for close to 90 medicinal indications. Many of these indications are related to treating infections. This contribution summarizes work done to date and identifies avenues for future research. MATERIALS AND METHODS Substantial work has already been done on the chemistry of especially Combretum and Terminalia species over many years. During the last decade we have focussed on bio-assay guided isolation of biologically active compounds with the aim of producing new effective antimicrobial products. RESULTS AND DISCUSSION Methods developed to facilitate this process and data on 25 compounds isolated from 7 species are presented. The large majority of compounds isolated were known, but the biological activities were not known. In practically all cases the antibacterial or antifungal activity of compounds isolated were much lower than expected from the activity of the crude extracts. It appears that synergism plays a role in antimicrobial activity of plant extracts and that the hope of isolating a single compound that can be used as a new agent to address antibiotic resistance has been frustrated. By simple manipulation such as selective extraction the activity of some crude extracts could however, be increased substantially and this offers a new approach to address antibiotic resistance via the herbal medicine industry. Practically all extracts obtained using intermediate polarity extractants had reasonable to very good activity with MICs as low as 40 microg/ml, validating the traditional use for infectious diseases. Aqueous extracts however, generally had hardly any activity. CONCLUSIONS The Combretaceae contains a diversity of antimicrobial compounds. Because poor people usually have only water available as extractant, it raises the question how plants growing in poor rural communities can be used to treat infections more effectively, and what the mechanism of activity of aqueous extracts used to treat infections in traditional medicine are.

The potential of South African plants against Mycobacterium infections

ETHNOPHARMACOLOGICAL RELEVANCE In South Africa, tuberculosis (TB) caused by Mycobacterium tuberculosis is the most commonly notified disease and the fifth largest cause of mortality, with one in ten cases of TB resistant to treatment in some areas. Many plants are used locally in traditional medicine to treat TB-related symptoms. AIM OF THE STUDY The aim was to summarize currently available knowledge on South African plants used to treat TB symptoms, and antimycobacterial efficacy of plant-derived extracts and compounds. MATERIALS AND METHODS The traditional uses of plants for respiratory ailments and TB were collated and tabulated. The antimycobacterial activity tests of extracts and chemical constituents of several of these plants and others using different methods and target organisms were summarized. RESULTS Almost 180 plants used for TB-related symptoms in South African traditional medicine were documented. About 30% of these have been tested for antimycobacterial efficacy, mostly against fast-growing, non-pathogenic Mycobacterium species. CONCLUSIONS Many plant species are used in traditional South African medicine to alleviate symptoms of TB, and several interesting leads have originated for further inquiry following in vitro antimycobacterial activity evaluation. However, much work remains to be done on the systematic assessment of anti-TB efficacy of local plants against pathogenic Mycobacterium species, both in vitro and in vivo.

Inflammation: the foundation of diseases and disorders. A review of phytomedicines of South African origin used to treat pain and inflammatory conditions.

Great interest in herbal medicine as a potential source of phytopharmaceuticals has created the need to review common factors responsible for major diseases and body disorders. This review shows one such common factor in inflammation and the role herbal medicine can play. Traditional medicinal herbal remedies in the southern African region have long been used to treat various pain- or inflammation-related symptoms. Although the precise mechanisms of action of many herbal drugs have yet to be determined, some of them have been shown to exert anti-inflammatory and/or antioxidant effects in a variety of cells in the human and animal bodies. There is increasing evidence to indicate that both peripheral and central nervous system cells play a prominent role in the chronic inflammatory responses in the body system and anti-inflammatory herbal medicine and its constituents are being proved to be a potent protector against various pro-inflammatory mediators in diseases and disorders. These mediators have therefore been suspected of being the functional basis of diseases and disorders. The structural diversity of these medicinal herbs makes them a valuable source of novel lead compounds against the therapeutic molecular targets, cytokines and mediators, that have been newly discovered by the platforms of genomics, proteomics, metabolomics and highthroughput technologies. This article reviews the basic mechanisms of inflammation and the potential of 123 southern African plant species to be effective as chronic inflammatory disease preventive agents. With one third of these species there are no indications of the chemical composition, indicating possible subjects for further research.

Ethnoveterinary use of southern African plants and scientific evaluation of their medicinal properties

AIM OF THE STUDY Livestock keepers in many developing countries with restricted access to orthodox veterinary healthcare services commonly use traditional remedies to treat their animals when disease is encountered. This review collates the documented use of plants in South Africa for healing various ailments in domestic animals, and records bioactivity testing that has been carried out on these plants. MATERIALS AND METHODS A literature survey was conducted on the use of plants in South African ethnoveterinary medicine (EVM), as well as on biological activity investigations relating to their ethnoveterinary use where available. RESULTS The ethnoveterinary application of plants, and results of screening studies of EVM plant extracts in various bioassays is presented. For diseases such as coughs, wounds, skin diseases, mild diarrhoea and reproductive disorders, EVM may be a cheap and easily accessible alternative to expensive pharmaceuticals. Studies on biological activity of EVM plants can provide indications of promising leads for extracts that can be developed into standardized medications to be used on a commercial basis. Isolation studies on active plants may yield pure active compounds that could be chemically modified to optimize medicinal value and reduce possible toxic effects. CONCLUSION In South Africa, a large proportion of the population relies on traditional remedies to treat themselves and their animals for common diseases. Only a small percentage of EVM plants have been analysed for biological activity or toxic effects, and hence research in this field offers fertile possibilities for future investigation.

The value of plant extracts with antioxidant activity in attenuating coccidiosis in broiler chickens

Coccidiosis remains one of the most important diseases in the poultry industry and results in the annual loss of millions of US dollars by the poultry industry. In South Africa and other developing countries where a large percentage of the population is unemployed, cheap food production is necessary. If the control of the coccidian parasite could be made more economical, these savings could be passed on to the consumer. In Europe, where the economics are different, people are becoming more aware of the potential dangers of using antimicrobials in producing animal protein. A solution to both these problems could be the use of plant products that function by mechanisms other than those of chemotherapeutics, with the additional advantage of a natural origin. Antioxidant compounds could hold promise for the control of Eimeria infections due to the association of coccidial infection with lipid peroxidation of the intestinal mucosa. Four plant extracts with antioxidant activity were screened for their anticoccidial activity in vivo with toltrazuril as the positive control. Combretum woodii (160 mg/kg) proved to be extremely toxic to the birds, while treatment with Tulbaghia violacea (35 g/kg), Vitis vinifera (75 mg/kg) and Artemisia afra (150 mg/kg) resulted in feed conversion ratios similar to toltrazuril, and higher than the untreated control. T. violacea also significantly decreased the oocyst production in the birds. From this study we conclude that antioxidant-rich plant extracts have potential benefits in treating coccidial infections. The promising results obtained with T. violacea justify further studies on the potential value of the plant as a therapeutic or prophylactic anticoccidial agent.

Four pentacyclic triterpenoids with antifungal and antibacterial activity from Curtisia dentata (Burm.f) C.A. Sm. leaves.

ETHNOPHARMACOLOGICAL RELEVANCE Curtisia dentata is used in southern Africa to treat various diseases of bacterial and fungal origin in humans and animals to such a degree that the species is vulnerable and declining [Dold, A.R., Cocks, M.L., 2001. Traditional veterinary medicine in the Alice district of the Eastern Cape Province, South Africa. South African Journal of Science 97, 375-379]. Preliminary studies indicated good activity against Candida albicans. AIM OF THE STUDY The phytochemistry and antimicrobial activity of this plant species has not been extensively investigated, and a closer examination of the compounds responsible for antimicrobial activity was warranted. MATERIALS AND METHODS Broth microdilution assay and bioautography were used to evaluate antibacterial and antifungal activity in Curtisia dentata leaf extracts and fractions. Bioassay-directed fractionation using column chromatography yielded four compounds characterised by spectroscopic methods. RESULTS Lupeol (1), betulinic acid (2), ursolic acid (3) and 2alpha-hydroxyursolic acid (4) were isolated from Curtisia dentata leaves. Betulinic acid, ursolic acid and 2alpha-hydroxyursolic acid appreciably inhibited fungal growth with MIC values ranging from 8 to 63mug/mL. CONCLUSIONS The isolation of four antibacterial and antifungal triterpenoids is reported for the first time from Curtisia dentata. This study provides information on the antimicrobial compounds of this species, as well as a preliminary rationale for the use in traditional South African medicine.

Antimicrobial activity and cytotoxicity of triterpenes isolated from leaves of Maytenus undata (Celastraceae)

BackgroundPlants of the genus Maytenus belong to the family Celastraceae and are widely used in folk medicine as anti-tumour, anti-asthmatic, analgesic, anti-inflammatory, antimicrobial and anti-ulcer agents, and as a treatment for stomach problems. The aim of this study was to isolate and identify active compounds with antifungal activity from Maytenus undata after a preliminary study highlighted promising activity in crude extracts.MethodsSequential extracts of M. undata leaves prepared using hexane, dichloromethane (DCM), acetone and methanol (MeOH) were tested for activity against Cryptococcus neoformans, a fungal organism implicated in opportunistic infections. Bioassay-guided fractionation of the hexane extract using C. neoformans as test organism was carried out to isolate antifungal compounds. The cytotoxicity of compounds isolated in sufficient quantities was evaluated using a tetrazolium-based colorimetric cellular assay (MTT) and a haemagglutination assay (HA).ResultsThe hexane extract was most active with an MIC of 20 μg/ml against C. neoformans. The triterpene compounds friedelin (1), epifriedelanol (2), taraxerol (3), 3-oxo-11α-methoxyolean-12-ene-30-oic acid (4), 3-oxo-11α-hydroxyolean-12-ene-30-oic acid (5) and 3,11-dihydroxyolean-12-ene-30-oic acid (6) were isolated. Compound 6 was isolated for the first time from a plant species. The antimicrobial activity of compounds 1, 3, 5 and 6 was determined against a range of bacteria and fungi implicated in opportunistic and nosocomial infections. Compounds 5 and 6 were the most active against all the tested microorganisms with MIC values ranging between 24 and 63 μg/ml, except against Staphylococcus aureus which was relatively resistant. Compounds 1 and 3 had a low toxicity with an LC50 > 200 μg/ml towards Vero cells in the MTT assay. Compounds 5 and 6 were toxic with LC50 values of 6.03±0.02 and 2.98±0.01 μg/ml, respectively. Compounds 1 and 3 similarly were not toxic to the red blood cells (RBCs) but compounds 5 and 6 were toxic, showing HA titer values of 1.33 and 0.67 respectively.ConclusionsCompounds 5 and 6 were the most active but were also relatively cytotoxic to monkey kidney cells and red blood cells, while the other isolated compounds were less active and less cytotoxic.

The antiviral activity of six South African plants traditionally used against infections in ethnoveterinary medicine

Viral infections remain a major threat to humans and animals and there is a crucial need for new antiviral agents especially with the development of resistant viruses. The hexane, dichloromethane, acetone and methanol extracts of six plant species selected for their traditional use against infections were tested for in vitro antiviral activity against canine distemper virus (CDV), canine parainfluenza virus-2 (CPIV-2), feline herpesvirus-1 (FHV-1) and lumpy skin disease virus (LSDV). All extracts were tested for their cytotoxicity using a colorimetric tetrazolium-based (MTT) assay and were tested for antiviral efficacy at concentrations below CC(50) values on the various cell types used in this study. The antiviral activity of extracts was tested using virucidal and attachment assays. In the virucidal assay, extracts were incubated with virus prior to infection. The most potent inhibition was observed with the acetone and methanol extracts of Podocarpus henkelii against CDV and LSDV, which inhibited replication of the viruses by >75% at 3μg/ml with selectivity index (SI) values ranging between 12 and 45. Excellent activity was also found with the hexane extracts of Plumbago zeylanica and Carissa edulis against CDV, with the extracts reducing viral-induced CPE by 50% and 75% respectively. The hexane extract of C. edulis had moderate activity against FHV-1 with EC(50)<70μg/ml and SI value <2. Only the acetone extract of P. henkelii moderately inhibited replication of LSD virus in the attachment assay, with low activity in other extracts. Of the four extracts with significant antiviral activity, two were prepared from P. henkelii. Therefore, future work will focus on isolating and characterizing the substance(s) responsible for bioactivity in extracts of this species.

The traditional use of plants to manage candidiasis and related infections in Venda, South Africa

ETHNOPHARMACOLOGICAL RELEVANCE This paper presents results of an ethnobotanical survey of medicinal plants used for the management of candidiasis and related fungal infections in the Venda area, South Africa. MATERIALS AND METHODS Ethnobotanical data about the uses of plants were gathered from eleven rural traditional healers using semi-structured interviews. RESULTS A total of 45 species belonging to 24 different families were identified, of which the dominant family was the Fabaceae with 13 species (28.9%) followed by the Asteraceae and Solanaceae with 3 species each (6.7 %). A total of 28 of these plant species (62.2%) have been shown to have anticandidal activity and 14 species (31%) have been recorded for antifungal uses in the literature. Amongst the 45 species recorded, 51% were trees, 33% were shrubs, and 16% were herbs. The most widely used plant species were Acacia caffra, Clerodendrum glabrum, Croton gratissimus, Elaeodendron transvaalense, Faurea saligna, Hippocratea longipetiolata, Osyris lanceolata, Richardia brasiliensis, Schkuhria pinnata, Schotia brachypetala, Spilanthes acmella, Strychnos potatorum, Vangueria infausta subsp. infausta and Withania somnifera. The plant parts mostly used in the therapeutic preparations were roots (27.7%), bark (23.2%), and a combination of roots, bark (18.7%) and leaves (14.3%). Decoctions (44.4%), infusions (20%), macerations (17.7%), burning (11.4%) and paste (6.5%) were used. Most of the herbal remedies were administered orally. The main factors threatening the conservation status of these plants are unsustainable methods of harvesting, logging for firewood, building materials and crafts. CONCLUSION The Venda area is rich in plant diversity and local indigenous knowledge of medicinal plants can play an important role as a model for low cost primary health care. Further studies are in progress to validate the indigenous plants recorded as traditional remedies in this area.

Antifungal activity and cytotoxicity of isolated compounds from leaves of Breonadia salicina

ETHNOPHARMACOLOGICAL RELEVANCE Breonadia salicina is used traditionally to treat wounds, ulcers, fevers, headaches, and fungal infections. The aim of this study was to investigate the antifungal activity of the plant extract and compounds isolated there from. MATERIALS AND METHODS Leaf extracts of Breonadia salicina were screened for antifungal activity against seven plant pathogens: Aspergillus niger, Aspergillus parasiticus, Colletotrichum gloeosporioides, Trichoderma harzianum, Penicillium expansum, Penicillium janthinellum and Fusarium oxysporum. Bioautography assay was used to determine the presence and number of antifungal compounds of the plant extracts. Bioassay-guided fractionation using column chromatography of the chloroform extract led to the isolation of four antifungal compounds. Nuclear Magnetic Resonance (NMR) spectroscopy, Mass Spectrometry (MS) and Electron Impact Mass Spectrometry (EIMS) were used for the identification of antifungal compounds. Cytotoxicity of the chloroform crude extract and isolated compounds was determined using the MTT (3-(4,5-dimethylthiazol)-2,5-diphenyl tetrazolium bromide) assay against Vero monkey kidney cells. RESULTS Compound 1 was identified as ursolic acid, while compounds 2, 3 and 4 were not identified conclusively owing to the presence of mixtures of long chain fatty acids. Compounds 3 and 4 had good antifungal activity against Aspergillus parasiticus and Penicillium janthinellum with MIC values of 10 and 16 µg/ml respectively. Compound 2 and ursolic acid had some activity with MIC values ranging between 20 and 250 µg/ml. The crude extract was less toxic to the Vero cells (LC50=82 µg/ml) than ursolic acid (LC50=25 µg/ml). Compounds 2 and 3 were not toxic at the highest concentration tested (LC50=200 µg/ml). Compound 4 was the most toxic to the cells with an LC50 of 35 µg/ml. CONCLUSIONS The results support the traditional use of Breonadia salicina for antifungal applications, and demonstrate the potential value of developing antifungal compounds from plant natural products. Indications of toxicity should be evaluated at an early stage as the selectivity of the product in affecting fungi preferentially to plant or mammalian cells should be identified when assessing the potential usefulness of the product.