Flavonoids of Chromolaena odorata (L.) R.M.King & H.Rob. as potential leads for treatment against tuberculosis

Tuberculosis (TB) is currently rated as the 13th leading cause of mortality and the second leading cause of death after COVID-19, and above AIDS. Existing challenges relating to the development of multidrug-resistant strains and dangerous side effects of currently used drugs add impetus to the search for additional TB treatments. Hence, interest has grown in the use of medicinal plants as a source of bioactive preparations with efficacy against TB-causing organisms, and also with the ability to ameliorate the negative effects of TB drugs. This study aimed to evaluate the antimycobacterial and hepatoprotective potentials of extracts and isolated flavonoid compounds from invasive Chromolaena odorata. Test organisms used were pathogenic Mycobacterium bovis and M. tuberculosis H37RV, and the fast-growing M. aurum, M. fortuitum and M. smegmatis. The selectivity index (SI) values of the test substances were determined through cytotoxicity assays to promote these extracts and compounds as leads for the development of effective and safe anti-tubercular drugs. The antimycobacterial activity was evaluated using a serial microdilution method, and the SI was calculated from the 50% lethal concentrations calculated from cytotoxicity tests. Hepatoprotective activity was determined using HepG2 liver cells treated with rifampicin as a toxin. The extracts and compounds had a range of antimycobacterial activity with minimum inhibitory concentration (MIC) values ranging from 0.031 to 2.5 mg/mL. Two flavonoid compounds, 5,7,4'-trimethoxy flavanone and 5‑hydroxy-3,7,4'-trimethoxyflavone showed promising antimycobacterial potential, and minimal toxicity was observed, as most SI values were higher than 1. The flavonoid compound 5,7,4'-trimethoxy flavanone had the highest SI (6.452), which was against M. tuberculosis H37RV. The HepG2 cells were reduced to 65% due to toxicity by rifampicin, however, the flavonoid compounds were able to improve cell viability to between 81 and 89% at different concentrations tested. Results obtained indicate that C. odorata may serve as a lead for the development of safe and effective antimycobacterial and hepatoprotective drugs.

Antibacterial and anti-inflammatory activity of plant species used in traditional poultry ethnomedicine in Zimbabwe: A first step to developing alternatives to antibiotic poultry feed additives

ETHNOPHARMACOLOGICAL RELEVANCE

Global interest in phytogenic feed additives as alternatives to antibiotics in feed has been spurred by the banning of antibiotic growth promoters by several countries. Suitable plant extracts for development of phytogenic feed additives should have therapeutic value and should also be safe.

AIM OF STUDY

The aim of this study was to evaluate the antibacterial, antioxidant and anti-lipoxygenase activities as well as cytotoxicity of selected plant species used in poultry ethnomedicine in Zimbabwe.

METHODS

Antibacterial activity was determined against three ATCC strains (Staphylococcus aureus, Escherichia coli, Salmonella Enteritidis) and two clinical strains isolated from chickens (Escherichia coli and Salmonella Gallinarum) using a two-fold serial microdilution assay. Qualitative antibacterial bioautography was also carried out using the ATCC strains. Antioxidant activities of crude acetone and methanol extracts were determined using free radical scavenging assays whilst anti-lipoxygenase activity was evaluated using a ferrous oxidation-xylenol orange (FOX) assay. Cytotoxicity was evaluated using a tetrazolium-based colorimetric assay (MTT assay) on Vero monkey kidney cells.

RESULTS

Erythrina abyssinica had the best antibacterial activity against both ATCC strains and clinical strains with minimum inhibitory concentration (MIC) values ranging from 0.02 to 0.156 mg/ml. Aloe greatheadii, Adenia gummifera (leaves), Senna singueana and Aloe chabaudii had moderate activity against the poultry pathogens. Bioautography showed that all ten plant species have antibacterial activity against the tested microorganisms with E. abyssinica and S. singueana having prominent bands of inhibition against both Gram-negative and Gram-positive bacteria. The acetone extract of S. singueana and the methanol extract of Euphorbia matabelensis had the most powerful antioxidant activities with mean IC₅₀ values of 1.43 μg/ml and 1.31 μg/ml respectively in the ABTS assay which were comparable with those of the positive controls (ascorbic acid and trolox). Bobgunnia madagascariensis, A. chabaudii, E. abyssinica and Tridactyle bicaudata extracts had reasonable antioxidant activity. The S. singueana extract had the most potent anti-lipoxygenase activity with a mean IC₅₀ value of 1.72 μg/ml. The cytotoxicity results showed that only the acetone extracts of A. greatheadii and S. singueana were relatively safe at concentrations that were active against the tested microorganisms (selective index >1). Regarding anti-lipoxygenase activity, extracts of B. madagascariensis, S. singueana, T. bicaudata and E. matabelensis were more active than toxic (selective index >5) indicating anti-inflammatory potential.

CONCLUSIONS

This study showed that S. singueana had a cocktail of therapeutic activity and supports further investigation of this plant species for development of phytogenic poultry feed additives. Other plant species with noteworthy biological activities include B. madagascariensis, E. abyssinica, A. greatheadii, T. bicaudata and E. matabelensis.

Anthelmintic and antimycobacterial activity of fractions and compounds isolated from Cissampelos mucronata

ETHNOPHARMACOLOGICAL RELEVANCE

Cissampelos mucronata A. Rich., a perennial climber belonging to the family Menispermaceae, has been used traditionally to treat parasites and tuberculosis-related symptoms. Co-infection of helminth parasites and tuberculosis-causing pathogens heightens the risk of developing active tuberculosis.

AIM OF THE STUDY

The aim was to isolate and characterize antimycobacterial compounds from Cissampelos mucronata and to investigate their antibiofilm and anthelmintic efficacy as well as cytotoxicity.

MATERIALS AND METHODS

The acetone extract of C. mucronata leaves and stems was fractionated by vacuum liquid chromatography using hexane, ethyl acetate, acetone and methanol:chloroform (3:7). Separation of the active ethyl acetate fraction by column and preparative thin layer chromatography led to the isolation and identification of five compounds using NMR and LC-MS, as well as GC-MS for non-polar compounds. The anthelmintic, antimycobacterial, antibiofilm, antioxidant and anti-inflammatory effects as well as cytotoxicity of the fractions and compounds were determined.

RESULTS

The ethyl acetate fraction had the best antimycobacterial activity (MIC = 0.015-0.08 mg/ml). The fractions were relatively non-toxic to Vero cells (0.03-0.79 mg/ml) and had good anti-inflammatory and antibiofilm effects. Five compounds were identified as stigmasterol, hentriacontane, simiarenol, nonacosene and carbonic acid. Nonacosene had moderate anthelmintic effects but poor antimycobacterial activity (MIC = 0.375 mg/ml). Nonacosene and hentriacontane had good biofilm inhibitory effect (90-100%).

CONCLUSIONS

This study reveals that C. mucronata is a potential source of promising compounds with a range of useful bioactivities that support its use in traditional medicine. Development of plant-based remedies may assist in reducing the impact of co-infections with helminth parasites and tuberculosis-causing mycobacteria.

Isolation and characterisation of nematicidal compound, leolorin C, from Leonotis leonurus acetone leaf extract

ETHNOPHARMACOLOGICAL RELEVANCE

Leonotis leonurus (L.) R.Br. (Lamiaceae) is a perennial shrub native to South Africa used to treat various diseases including digestive tract problems, intestinal worms and constipation.

AIM OF THE STUDY

The aim was to isolate and characterise nematicidal compounds from leaves of L. leonurus.

MATERIALS AND METHODS

Bioassay-guided fractionation was carried out using the free-living nematode Caenorhabditis elegans as a model organism. Structural elucidation of the purified compound was carried out using NMR spectroscopic analyses and UPLC-QTOF-MS. The fractions and the isolated compound were tested for nematicidal activity on motility of plant-parasitic Meloidogyne incognita juveniles (J2s) and J2 hatch inhibition. Further screening was done to determine the minimum inhibitory concentration (MIC) of the fractions against bacterial phytopathogens and cytotoxicity against Vero kidney cells.

RESULTS

Leoleorin C isolated from L. leonurus had moderate activity against C. elegans juveniles (34%) but was not active against J2 motility and J2 hatch of M. incognita. Thus, activity against the free-living C. elegans did not correspond with efficacy against plant-parasitic nematodes. Leoleorin C was not active against the tested bacterial phytopathogens, but some activity was observed in the bioautography assay against Clavibacter michiganensis subsp. michiganensis, the organism causing bacterial canker in tomatoes. The plant extract, fractions and leolorin C were relatively non-toxic to Vero cells with LC50 values greater than 0.01 mg/mL.

CONCLUSION

The crude extract of L. leonurus and fractions may be useful in developing complementary treatments for controlling nematodes and phytopathogens. This study does not support the use of free-living nematodes as a model to isolate anti-parasitic compounds from plants.

Invasive alien plants and weeds in South Africa: A review of their applications in traditional medicine and potential pharmaceutical properties

ETHNOPHARMACOLOGICAL RELEVANCE

Traditional pharmacopoeias are constantly evolving and adapting, hence the assimilation of alien plants and weeds into traditional systems of healing. Invasive plants are detrimental to the ecosystem, however they are also potential sources of secondary metabolites with useful biological activities.

AIM OF THE REVIEW

The aim of this review was to investigate published reports of traditional use and biological activity of declared invasive alien plants and other weeds in South Africa.

MATERIALS AND METHODS

Information was retrieved from scientific databases including Scopus, Web of Science, ScienceDirect, Google Scholar, PubMed, Chemical Abstracts Services and books, theses, dissertations and technical reports. Keywords used for the search engines were "South Africa" or "southern Africa" in conjunction with "(native weeds OR alien invasive)" AND "medicinal". Separate searches were conducted on the individual invasive plant species recorded as having been used in ethnobotanical surveys to determine their known biological activities and chemical components.

RESULTS

A total of 89 plant species regarded as invasive species or weeds in South Africa were identified as being used in traditional medicine. The most commonly mentioned plant family was the Asteraceae with a total of 15 species followed by the Fabaceae and Solanaceae with 6 species each. Of the 89 species recorded, 68% were reported to have traditional usage with both phytochemical and biological data available. A history of traditional usage coupled with biological data was available for 12% of species. Records of traditional usage alone were linked to 11% of species. Invasive alien species comprised 61% of recorded species, while native and non-invasive alien weeds formed the remaining 39%.

CONCLUSIONS

The exploration of alternative uses for weeds and particularly invasive plants, whether native or alien, as medicines for possible commercialisation may lead to innovative mechanisms for putting such species to good use.

Differentiation of Tarchonanthus camphoratus L. and Tarchonanthus parvicapitulatus P.P.J. Herman (Asteraceae) using electron microscopy, and comparison of their biological activities

ETHNOPHARMACOLOGICAL RELEVANCE

Tarchonanthus camphoratus L. complex has numerous medicinal uses amongst the sub-Saharan African populace, including treatment for bronchospasm. This study focused on providing scientific rationale for the traditional use of the extracts of T. camphoratus and T. parvicapitulatus. T. camphoratus L. complex has been published under diverse names by various taxonomists. Tarchonanthus parvicapitulatus was one of the newly described taxa, leaving Tarchonanthus camphoratus L. sens. strict. as a homogenous taxon. However, some of the morphological characters used tend to overlap, making it difficult to identify the different taxa.

AIMS

The aim of this study was to evaluate the bronchodilatory, antioxidant and toxicological properties of the leaves of T. camphoratus L. and T. parvicapitulatus. This study also aimed to use scanning electron microscopy (SEM) to assess the differences between T. camphoratus L. and T. parvicapitulatus.

MATERIALS AND METHODS

Thin layer chromatography (TLC) with vanillin as visualizing agent was used to qualitatively compare the phytoconstituents of the plant acetone extracts. The free radical scavenging antioxidant qualitative assay was done by spraying TLC plates with DPPH free radical. The bronchodilatory effects of the aqueous extracts were assessed using pre-contracted guinea pig trachea. The effects of the extracts of T. camphoratus L. and T. parvicapitulatus on superoxide and ATP production was also investigated on isolated human neutrophils. A micromorphology study was done using scanning electron microscopy to study the leaves.

RESULTS

Different compounds were visualized on the TLC plates with more than 40 compounds of intermediate polarity. The TLC plates sprayed with DPPH revealed the presence of 20 and 23 antioxidant compounds for T. camphoratus and T. parvicapitulatus respectively. Upon pre-contraction of the tracheal smooth muscles, the aqueous extracts of T. parvicapitulatus significantly relaxed the trachea while the relaxation observed for T. camphoratus was not significant. All the tested concentrations had a dose dependent inhibitory effect on superoxide production. The crude extract of T. parvicapitulatus at the highest concentration (10 mg/ml) significantly decreased ATP production while a non-significant increase in ATP production was observed for T. camphoratus at the highest concentration (10 mg/ml) when compared with the control. The micromorphology study was useful in revealing the presence of trichomes on the upper leaf surface of the studied taxa.

CONCLUSIONS

The results obtained from this study showed that the studied plant extracts had bronchodilatory effects on contracted guinea pig trachea and could also inhibit the production of free radicals including superoxide anions. To the best of our knowledge, this is the first report on the bronchodilatory activity of T. camphoratus and T. parvicapitulatus. The micromorphological studies were useful in distinguishing between the two species, confirming that T. camphoratus L. and T. parvicapitulatus are different taxa. This study provides evidence to support the traditional use of T. camphoratus and T. parvicapitulatus in managing bronchospasm.

Scientific rationale for traditional use of plants to treat tuberculosis in the eastern region of the OR Tambo district, South Africa

ETHNOPHARMACOLOGICAL RELEVANCE

Tuberculosis (TB) remains a major health problem for humans worldwide, and was responsible for 1.4 million human deaths in 2015 alone. Although there is treatment for TB, emerging multi-drug, extensively drug and totally drug resistant forms of this disease, as well as co-infection with human immunodefiency virus (HIV) continue to worsen the situation. South Africa is among countries with reported traditional use and published documentation of such knowledge concerning the use of plants against TB. Based on a previous study where plants used traditionally for treating TB in the eastern region of OR Tambo district, South Africa, were documented, the present study aimed to determine the antimycobacterial effect, cytotoxicity and genotoxicity of plants selected from that list.

MATERIAL AND METHODS

Acetone, 70% ethanol, cold and hot water extracts were tested for antimycobacterial activity against saprophytic Mycobacterium species including M. aurum, M. bovis BCG, M. gordonae, M. fortuitum, and M. smegmatis using a microdilution method. Extracts with MIC values less than 1 mg/ml against at least three Mycobacterium strains were evaluated for antimycobacterial activity against pathogenic Mycobacterium strains including M. tuberculosis H37RV, M. tuberculosis and M. bovis, cytotoxicity (against Vero monkey kidney and bovine dermis cells), and genotoxicity (against Salmonella typhimurium TA98 and TA100).

RESULTS

The MIC values of the extracts ranged from 0.02 to 2.50 mg/ml, LC₅₀ values of twenty-nine extracts ranged from 0.001 to > 1 mg/ml and the highest selectivity index was 79.50, an extremely promising value. Phymaspermum acerosum roots and leaves (ethanol and water) extracts had the best MIC value (0.02 mg/ml) against at least one Mycobacterium strain. It was interesting to note the lack of cytotoxicity of these extracts with the highest selectivity index value of 39.75. Pterocelastrus echinatus bark acetone and Protorhus longifolia leaf hot water extracts were the most cytotoxic with LC₅₀ = 0.001 and 0.008 mg/ml, respectively, whereas Pittosporum viridiflorum bark water extract was genotoxic. Among non-pathogenic strains, M. gordonae, M. aurum, M. smegmatis showed good correlation of activity with pathogenic M. tuberculosis H37Rv, M. tuberculosis and M. bovis, however, M. aurum was the best predictor with Mycobacterium tuberculosis H37Rv (correlation coefficient value = 0.73).

CONCLUSION

The results indicate that Heteromorpha trifoliata and Phymaspermum acerosum should be investigated further for antimycobacterial efficacy against drug resistant strains of Mycobacterium.

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.

Ethnobotany, phytochemistry, toxicology and pharmacological properties of Terminalia sericea Burch. ex DC. (Combretaceae) - A review

ETHNOPHARMACOLOGICAL REFERENCE

The use of medicinal plants in the treatment of infections is ancient. A wide variety of ethnotherapeutic properties and pharmacological actions has been attributed to Terminalia sericea. Studies by various groups of investigators reveal that it is a multipurpose medicinal plant used mostly in the treatment of diarrhoea, sexually transmitted infections, skin rashes, tuberculosis and other infections. The current paper is aimed at providing an overview of the ethnomedicinal uses, toxicology, pharmacology and the phytochemistry of Terminalia sericea.

MATERIALS AND METHODS

Information was retrieved using various search engines, including Pubmed, Science Direct, Google Scholar, Scielo, SciFinder and Scopus. The key words used included Terminalia sericea, secondary metabolites, phytochemistry, biological activity, pharmacology, ethnobotanical survey, medicinal uses, safety, toxicology and other related words.

RESULTS

Terminalia sericea is an important medicinal plant which possesses anti-HIV, anti-fungal, anti-bacterial, anticancer, lipolytic, wound healing, antiparasitic, anti-inflammatory and anti-oxidant activity, as the most valuable biological activities, thus lending pharmacological support to the plant's folkloric uses in indigenous medicine. Toxicologically, the extracts and isolated compounds from the plant species may have mild toxic effects. Phytochemically, the plant species possesses valuable compounds including triterpenes, alkaloids and flavonoids which may well contribute to its biological activity.

CONCLUSIONS

Terminalia sericea contains secondary metabolites which are valuable in the treatment of a variety of human infections, including community acquired infections which may be prevalent in developing countries. The degree of toxicity reported in various extracts warrants further exploration of the cytotoxicity of the plant species, both against normal human cell lines and in vivo. Moreover, the acetylcholinesterase inhibitory and anti-inflammatory effects also need to be further investigated as there are only a few reports from the literature on these aspects. There is also a need to further understand the mode of action of the extracts against various enzymes relating to inflammation. Antioxidant activity of the plant extracts against various forms of free radicals needs to be investigated. Although T. sericea is reported to be used for ethnoveterinary infections, there are no scientific reports on the anti-parasitic activity of the plant species against common animal parasites.

Novel Mycobacterium avium Complex Species Isolated From Black Wildebeest (Connochaetes gnou) in South Africa

A study was undertaken to isolate and characterize Mycobacterium species from black wildebeest suspected of being infected with tuberculosis in South Africa. This led to the discovery of a new Mycobacterium avium complex species, provisionally referred to as the Gnou isolate from black wildebeest (Connochaetes gnou). Sixteen samples from nine black wildebeest were processed for Mycobacterium isolation. Following decontamination, samples were incubated in an ordinary incubator at 37°C on Löwenstein-Jensen slants and in liquid medium tubes using the BACTEC^™ MGIT^™ 960 system, respectively. Identification of the isolate was carried out by standard biochemical tests and using the line probe assay from the GenoType^® CM/AS kit (Hain Lifescience GmbH, Nehren, Germany). The DNA extract was also analysed using gene sequencing. Partial gene sequencing and analysis of 16S rRNA gene, and 16S-23S rRNA (ITS), rpoB and hsp65 and phylogenetic analyses by searching GenBank using the BLAST algorithm were conducted. Phylogenetic trees were constructed using four methods, namely Bayesian inference, maximum likelihood, maximum parsimony and neighbour-joining methods. The isolate was identified as Mycobacterium intracellulare using the GenoType^® CM/AS kit and as Mycobacterium avium complex (MAC) by gene sequencing. The gene sequence targeting all the genes, ITS, 16S rRNA, rpoB and hsp65 and phylogenetic analyses indicated that this isolate presented a nucleotide sequence different from all currently published sequences, and its position was far enough from other MAC species to suggest that it might be a new species.

Securidaca longipedunculata Fresen (Polygalaceae): a review of its ethnomedicinal uses, phytochemistry, pharmacological properties and toxicology

ETHNOPHARMACOLOGICAL RELEVANCE

Securidaca longipedunculata Fresen (Polygalaceae) is a multi-purpose plant with a long history of use in African traditional medicine to treat various sexually transmitted infections, hernias, coughs, fever, ascariasis, constipation, headaches, rheumatism, stomach ache, malaria, tuberculosis, pain, epilepsy, pneumonia, skin infections, and it is also used as an aphrodisiac for men. The current paper provides an overview of the present phytochemistry, toxicology, ethnomedicinal uses and pharmacological properties of S. longipedunculata.

MATERIALS AND METHODS

The information reported in this paper was collected from a literature search using various computerised databases including ScienceDirect, Scopus, Scielo, PubMed and Google Scholar. The extra information was sourced from various academic dissertations, theses and botanical books.

RESULTS

Phytochemically, extracts from various parts of S. longipedunculata, especially the root bark, contain numerous valuable compounds including xanthones, some benzyl benzoates and triterpene saponins amongst others. Toxicity studies, both in vivo and in vitro, revealed that extracts are only toxic at relatively high concentrations. Furthermore, extracts have antimicrobial, antioxidant, antiparasitic, anti-diabetic, anti-inflammatory, antimalarial, insecticidal, pesticidal, and anticonvulsant properties.

CONCLUSIONS

S. longipedunculata is an important plant species with potential benefits in the treatment of transmissible and infectious diseases, including malaria, tuberculosis, and those caused by community acquired microorganisms. Although extracts from this species generally have little toxicity at low concentrations, further efforts are required to investigate the potential toxicity of S. longipedunculata. The antimicrobial properties of extracts and purified compounds against microorganisms causing sexually transmitted infections are also deserving of further research. Moreover, the pharmacokinetic properties of extracts and compounds of the species need to be explored as there is insufficient data available on these aspects.

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.

Isolation and characterisation of novel antioxidant constituents of Croton zambesicus leaf extract

A 1,1-diphenyl-2-picrylhydrazyl (DPPH)-activity-directed fractionation was used to target antioxidant constituents of the ethyl acetate fraction obtained from a 20% aqueous methanol crude extract of Croton zambesicus leaf. Repeated column chromatography of the fraction on silica gel and Sephadex LH-20 led to the isolation of a new natural product, identified as quercetin-3-O-β-6″(p-coumaroyl) glucopyranoside-3'-methyl ether, helichrysoside-3'-methyl ether (1), along with kaempferol-3-O-β-6″(p-coumaroyl) glucopyranoside, tiliroside (2) and apigenin-6-C-glucoside, isovitexin (3) as the antioxidant constituents. The structures of the isolated compounds were elucidated using spectroscopic techniques, namely NMR (1D and 2D) and mass spectrometry. Compounds 1 and 2 are reported from this species for the first time. In the qualitative antioxidant assay, the three isolated compounds instantly bleached the DPPH (0.2% MeOH) purple colour indicating antioxidant activity. In the quantitative antioxidant assay, all the isolated compounds demonstrated weak antioxidant activity compared to quercetin and rutin used as positive control antioxidant agents. The compounds displayed little to no cytotoxicity against Vero cells in an in vitro assay. The presence of these antioxidant compounds in the leaf extract of C. zambesicus could provide a rationale for the ethnomedicinal use of the plant in the management of oxidative-stress-related diseases in folk medicine.

Antimycoplasmal activity of some plant species from northern Nigeria compared to the currently used therapeutic agent

CONTEXT

Mycoplasma spp. are obligate parasites of humans and animals. But due to the special requirements needed to culture Mycoplasma in the laboratory, little or no research has been done to evaluate the efficacy of medicinal plants on the organism.

OBJECTIVE

To screen medicinal plants traditionally used to treat infections for possible antimycoplasmal and cytotoxic activities.

MATERIALS AND METHODS

Acetone extracts of 21 Nigerian medicinal plants were analyzed for antimycoplasmal and cytotoxicity activities using the metabolic inhibition and colorimetric methods, respectively. The extract with the best antimycoplasmal activities was also analyzed for its phytochemical constituents using the desktop method.

RESULTS

Calotropis procera (Aiton) R.Br (Asclepiadaceae) extract had the best antimycoplasmal effect with a minimum inhibitory concentration (MIC) of 80 µg/mL and minimum mycoplasmacidal concentration (MMC) of 160 µg/mL. This extract contained saponins, tannins, cardiac glycosides, alkaloids, and flavonoids. The extract of Vernonia amygdalina Delile (Compositae) was the most cytotoxic with median lethal concentration (LC(50)) of approximately 17 µg/mL, and that of Anacardium occidentale L. (Anacardiaceae) was the least cytotoxic with an LC(50) of approximately 1919 µg/mL.

DISCUSSION

Calotropis procera is a promising plant for an alternative antimycoplasmal agent because the crude acetone extract had a higher mycoplasmacidal activity than the conventional drug tylosin, which is currently used in treatment of the disease in Nigeria.

CONCLUSION

The crude extract of Calotropis procera is worth investigating for the development of a potent agent against cattle Mycoplasma, which has long defied solution by conventional chemotherapy.

Curtisia dentata (Cornaceae) leaf extracts and isolated compounds inhibit motility of parasitic and free-living nematodes

Haemonchus contortus and Trichostrongylus colubriformis are among the most important parasitic nematodes of small ruminants. Caenorhabditis elegans, a free-living nematode, is used as a model for evaluating anthelmintic activity of a variety of test substances. Extracts of several medicinal plants are useful in vitro and in vivo against nematode development. Extracts of Curtisia dentata, a South African medicinal plant, and compounds isolated from leaves of this plant were investigated for anthelmintic activity against T. colubriformis, H. contortus and C. elegans. The acetone and dichloromethane extracts were active against all nematodes at concentrations as low as 160 microg/ml. Betulinic acid and lupeol were active against the parasitic nematodes only at the high concentrations of 1000 and 200 microg/ml, respectively. All compounds were effective against C. elegans with active concentrations as low as 8 microg/ml. Betulinic acid was less active than lupeol and ursolic acid against C. elegans. The acetone and dichloromethane extracts were also active against C. elegans with a concentration of 0.31 mg/ml resulting in almost 80% inhibition of larval motility. The use of free-living nematodes may provide information on the activity of potential anthelmintics against parasitic nematodes. Extracts of various medicinal plant species may provide solutions to ill-health of small ruminants caused by parasitic nematodes in poor communities of southern Africa.

Antifungal efficacy of ten selected South African plant species against Cryptococcus neoformans

Fungal infections are a major threat to public health care. Cryptococcosis in humans and animals, caused by Cryptococcus neoformans, is a life-threatening disease. In a random antifungal screening of acetone leaf extracts of 400 tree species against Cryptococcus neoformans, the following plant species had good activity: Zanthoxylum capense (Thunb.) Harv. (Rutaceae), Morusmesozygia Stapf (Moraceae), Calodendrum capense (L.f.) Thunb. (Rutaceae), Catha transvaalensis Codd (Celastraceae), Cussonia zuluensis Strey (Araliaceae), Ochna natalitia (Meisn.) Walp. (Ochnaceae), Croton sylvaticus Hochst. ex C. Krauss (Euphorbiaceae), Maytenus undata (Thunb.) Blakelock (Celastraceae), Celtis africana Burm.f. (Ulmaceae), and Cassine aethiopica Thunb. (Celastraceae). Hexane, dichloromethane, acetone, and methanol extracts of these 10 plants were tested against Cryptococcus neoformans using bioautography and microdilution assays. Acetone extracted the highest quantity of plant material. Dichloromethane and hexane extracts of Maytenus undata showed clear bands in bioautography while the other species did not produce good results in bioautography. Maytenus undata extracts had promising antifungal activity against C. neoformans, with average minimum inhibitory concentration (MIC) of 0.09 mg/mL after 24 h and 0.18 mg/mL after 48 h incubation. Croton sylvaticus and Catha transvaalensis extracts also had good activity, with average MIC values of 0.07 mg/mL and 0.09 mg/mL, respectively. Because of the clear bands on bioautograms and low MIC values compared to the other plant species investigated, M. undata was identified as a good candidate for further studies.

Detection of antimicrobial compounds by bioautography of different extracts of leaves of selected South African tree species

The hexane, acetone, dichloromethane and methanol extracts of Combretum vendae A.E. van Wyk (Combretaceae), Commiphora harveyi (Engl.) Engl. (Burseraceae), Khaya anthotheca (Welm.) C.DC (Meliaceae), Kirkia wilmsii Engl. (Kirkiaceae), Loxostylis alata A. Spreng. ex Rchb. (Anacardiaceae), Ochna natalitia (Meisn.) Walp. (Ochnaceae) and Protorhus longifolia (Bernh. Ex C. Krauss) Engl. (Anacardiaceae) were screened for their antimicrobial activity. The test organisms included bacteria (Enterococcus faecalis, Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus), and fungi (Aspergillus fumigatus, Candida albicans, Cryptococcus neoformans, Microsporum canis and Sporothrix schenckii). A simple bioautographic procedure, involving spraying suspensions of the bacteria or fungi on thin layer chromatography (TLC) plates developed in solvents of varying polarities was used to detect the number of antibacterial and antifungal compounds present in the extracts. All the extracts had antimicrobial activity against at least one of the test microorganisms. This activity was denoted by white spots against a red-purple background on the TLC plates after spraying with tetrazolium violet. Twenty seven TLC plates; 9 for each solvent system and 3 different solvent systems per organism were tested in the bioautographic procedure. Of the bacteria tested, S. aureus was inhibited by the most compounds separated on the TLC plates from all the tested plants. Similarly, growth of the fungus C. neoformans was also inhibited by many compounds present in the extracts. Loxostylis alata appeared to be the plant extract with the highest number of inhibition bands when compared with other plants tested against both bacteria and fungi. This species was selected for in depth further study.

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 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.

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.

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.

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.

Antioxidant activity and cytotoxicity study of the flavonol glycosides fromBauhinia galpinii

The antioxidant activity of the crude extract and solvent fractions obtained from the leaves of Bauhinia galpinii was evaluated in terms of capacity to scavenge 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radicals. The crude extract and the more polar solvent fractions (ethyl acetate and butanol) showed considerable antioxidant activity. The antioxidant potential of the extracts, expressed as EC50, ranged between 28.85 +/- 1.28 microg mL(-1)and 118.16 +/- 6.41 microg mL(-1). L-Ascorbic acid was used as a standard (EC50 = 19.79 +/- 0.14 microM). Bioassay guided fractionation of the two active solvent fractions led to the isolation of three flavonoid glycosides, identified as: quercetin-3-O-galactopyranoside (1), myricetin-3-O-galactopyranoside (2), and 2''-O-rhamnosylvitexin (3). These compounds are reported for the first time from this species. The structures of the compounds were determined on the basis of spectral studies (1H NMR, 13C NMR and MS). Their antioxidant potential was evaluated using a DPPH spectrophotometric assay. Compound 2 had higher and 3 had lower antioxidant activity than L-ascorbic acid. No cytotoxic effects were displayed by compounds 1 and 3, but compound 2 was cytotoxic to Vero cells (LC50 = 74.68 microg mL(-1)) and bovine dermis cells (LC50 = 30.69 microg mL(-1)).

Evaluation of Athrixia bush tea for cytotoxicity, antioxidant activity, caffeine content and presence of pyrrolizidine alkaloids

In South Africa, Athrixia phylicoides DC. (bush tea) is widely used as a beverage, cough remedy and purgative. The commercialization of this tea in a similar vein to rooibos (Aspalathus linearis), is being considered. Traditional infusions and decoctions, as well as water and ethanol extracts, were prepared and screened. A related species, Athrixia elata Sond. (daisy tea), was included in many of the assays as a comparison. Extracts of Athrixia phylicoides and Athrixia elata were tested for toxic effects to brine shrimp larvae and the Vero kidney cell line. In both assays, the traditional preparations and aqueous extracts had little effect, but the ethanol extracts were relatively toxic. Antioxidant activity comparable to that found in rooibos was established. No detectable levels of caffeine were present in the Athrixia extracts following analysis using TLC and I/HCl spray reagent. Neither screening using spectrophotometry nor confirmation using gas chromatography-mass spectrometry analyses showed evidence of pyrrolizidine alkaloids in Athrixia phylicoides. Although a wider range of studies needs to be conducted prior to commercialization, these results support the development of bush tea as a healthy alternative to caffeine-containing beverages.

In vitro anthelmintic, antibacterial and cytotoxic effects of extracts from plants used in South African ethnoveterinary medicine

Many plants are used for ethnoveterinary purposes in South Africa, particularly in rural areas. Extracts of 17 plant species employed to treat infectious diseases were prepared using three solvents and the antibacterial activity of the extracts was determined against two Gram-positive and two Gram-negative bacteria. Anthelmintic activity was evaluated against the free-living nematode Caenorhabditis elegans and toxicity was determined using the brine shrimp larval mortality test. Most of the plant extracts demonstrated antibacterial activity, with the best minimum inhibitory concentration (MIC) being 0.1 mg mL(-1). More than a third of the extracts displayed anthelmintic activity. Toxic effects against brine shrimp larvae were shown by 30% of extracts, with the lowest LC(50) recorded as 0.6 mg mL(-1). The promising biological activity displayed by a number of plant extracts supports the ethnoveterinary use of these plants but in vivo tests are required to ascertain fully their medicinal properties and potential toxicity.

Is the use o f Gunnera perpensa extracts in endometritis related to antibacterial activity?

Rhizome extracts of Gunnera perpensa are used in traditional remedies in South Africa to treat endometritis both in humans and animals. An investigation was undertaken to determine whether this plant possesses antibacterial activity, which may explain its efficacy. Gunnera perpensa rhizome extracts were prepared serially with solvents of increasing polarity and tested for antibacterial activity. Test bacteria included the Gram-positive Enterococcus faecalis and Staphylococcus aureus and the Gram-negative Escherichia coli and Pseudomonas aeruginosa. A moderate to weak level of antibacterial activity in most of the extracts resulted, with the best minimal inhibitory concentration (MIC) value of 2.61 mg ml(-1) shown by the acetone extract against S. aureus. The extracts were also submitted to the brine shrimp assay to detect possible toxic or pharmacological effects. All the extracts were lethal to the brine shrimp larvae at a concentration of 5 mg ml(-1). The acetone extract was extremely toxic at 1 mg ml(-1), with some toxicity evident at 0.1 mg ml(-1). The remainder of the extracts generally displayed little activity at concentrations lower than 5 mg ml(-1). In summary, the results indicate that although the extracts demonstrated a level of pharmacological activity, the relatively weak antibacterial activity is unlikely to justify the use of G. perpensa rhizomes in the traditional treatment of endometritis. Rather, the slightly antibacterial nature of the rhizomes may contribute to an additive effect, along with their known uterotonic activity, to the overall efficacy of the preparation.

Assessing African medicinal plants for efficacy and safety: pharmacological screening and toxicology

This paper reviews progress in establishing the scientific rationale for and safety of traditional medicine use in Africa. Selected plants were screened for antibacterial, antifungal, anthelmintic, anti-amoebic, antischistosomal, antimalarial, anti-inflammatory and antioxidant activity, as well as psychotropic and neurotropic activity using appropriate in vitro tests. Isolation of active compounds, in almost all cases, provided scientific validation for the use of the plants in traditional medicine. Although plants used medicinally are widely assumed to be safe, many are potentially toxic. Where poisoning from traditional medicines has been reported, it is usually because the plants used have been misidentified in the form in which they are sold, or incorrectly prepared and administered by inadequately trained personnel. The issue of quality control may, in the interim, be addressed using chromatographic techniques.

Isolation of antibacterial fatty acids from Schotia brachypetala

In southern Africa, the roots of Schotia brachypetala are used by traditional healers to treat dysentery and diarrhoea. Activity-directed fractionation of the ethanol extract of the dried leaves 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 to a lesser extent, against the Gram-negative Escherichia coli and Klebsiella pneumoniae.

An investigation on the biological activity of Combretum species

Leaf extracts of 20 Combretum species, many of which are used in southern African traditional medicine, were screened for anti-inflammatory, anthelmintic, anti-bilharzia (antischistosomal) and DNA-damaging activity. Significant activity in more than one bioassay was exhibited by Combretum apiculatum, Combretum hereroense, Combretum molle and Combretum mossambicense. Ethyl acetate extracts were generally most active, followed by acetone and then water extracts.

Antibacterial, anthelmintic and anti-amoebic activity in South African medicinal plants

Hexane, ethanol and water extracts of plants used by South African traditional healers for treating stomach ailments were screened for antibacterial, anthelmintic and anti-amoebic activities. To evaluate antibacterial activity, the disc-diffusion assay was used against several Gram-positive and Gram-negative species. Minimal inhibitory concentration values were determined with a microdilution assay. Ethanolic extracts showed the greatest activity, and Gram-positive bacteria were the most susceptible microorganisms. The free-living nematode Caenorhabditis elegans was used in two different assays to evaluate anthelmintic activity. A microdilution technique was employed to investigate anti-amoebic activity against the enteropathogenic Entamoeba histolytica. 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.

Organ donors and nondonors. An American dilemma

The principal motive for organ donation in the United States remains altruism. Surveys suggest that if the life-threatening and critical shortage of cadaveric donor organs were appropriately understood by the public, an altruistic response would lead to increased donation. However, despite intense educational efforts appealing to altruism, cadaveric organ donation has not increased substantially while the number of patients in need of a life-saving organ has grown markedly. To understand why organ donation has not increased, a telephone survey and focus group sessions of volunteers who were either for or against donation (donors and nondonors, respectively) were reviewed. The focus group nondonors demonstrated a remarkable lack of trust in the fairness of organ allocation and in the success of transplantation; indeed, this mistrust extended to the entire medical profession. The donors in the focus groups, on the other hand, believed that the system worked equitably, although their knowledge about organ donation and transplantation was equivalent to that of nondonors. For organ donation to increase, efforts must be directed toward those who are not convinced that donation is for the common welfare. One way to increase organ donation is for physicians to educate their patients better regarding the equity and success of transplantation.