Buchu (Agathosma betulina and A. crenulata, Rutaceae) essential oils: their pharmacological action on guinea-pig ileum and antimicrobial activity on microorganisms

Buchu (Agathosma betulina and A. crenulata): Rightfully Forgotten or Underutilized?

Today, the term buchu refers to the two species in commerce, Agathosma betulina (P.J.Bergius) Pillans and Agathosma crenulata (L.) Pillans (Rutaceae). Its traditional use in urinary tract infections and related ailments made it a popular remedy, specifically in the US, in 19th century, but with the advent of antibiotics it became largely obsolete. Recent focus is on technological use and on the essential oil for use in the perfume and food-flavouring industry. A review of the scarce pharmacological research revealed moderate antimicrobial activity for a leaf extract but not the essential oil of both species in the MIC assay. In the 5-lipoxygenase (5-LO) assay the essential oil of both species revealed IC50 values of 50.37 ± 1.87 μg/ml and 59.15 ± 7.44 μg/ml, respectively. In another study 98% inhibitory activity was determined for 250 μg/ml of an ethanolic extract of A. betulina on cyclooxygenase (COX)-1 and a 25% inhibitory activity on COX-2. Analgesic activity of an ethanolic extract of A. betulina was shown in mice. Moderate antioxidant activity was determined for methanol:dichlormethane extracts of A. betulina and A. crenulata and an aqueous extract of A. betulina showed a Trolox equivalent antioxidant capacity (TEAC) of 11.8 µM Trolox. Recent in vitro studies with a commercial aqueous extract of buchu revealed increased uptake of glucose added to 3T3-L1 cell line, significant inhibition of the respiratory burst of neutrophils and monocytes, reduction in the expression of adhesion molecules and inhibition of the release of IL-6 and TNF-α. In diabetic rats the ingestion of aqueous buchu extract completely normalized the glucose level and in rats receiving a high fat diet the consumption of aqueous buchu extract resulted in less weight gain and less intraperitoneal fat gain as well as reduction of elevated blood pressure to normal associated with cardioprotective effects. Limitations in the hitherto conducted research lie in the undisclosed composition of the buchu extracts used and the difficulty in extrapolating data from animal studies to humans. Health claims for buchu products need to be substantiated by randomized, double-blind and placebo-controlled studies. Only then can they be promoted for their true therapeutic potential.

Antioxidant Activity of Metabolites from Coleonema Album (Rutaceae)

Coleonema album, a member of the South African ‘Fynbos’ biome, was evaluated for its antioxidant and free radical scavenging activity. Ethanol- and acetone-based extracts from plant material obtained from two different geographical areas were analysed. A bioassay-guided fractionation methodology was followed for screening of active compounds. The 1,1-diphenyl-2-picrylhydrazyl (DPPH)-TLC method revealed the presence of a number of antioxidants which were quantified by the DPPH-spectrophotometric assay and the oxygen radical absorbance capacity (ORAC) assay. The C. album extracts possessed significant in vitro antioxidant activity, a large portion of which appeared to be contributed by the phenolic compounds. In contrast, the reducing power of the extracts could not be correlated with the observed antioxidant activity. Identification and structural information of the active components were obtained by a combination of preparative TLC and LC-MS which revealed the presence of coumarin aglycones and glycosides. The results of this study indicate that C. album contains strong antioxidants that warrant further investigation into the relationship between the structure and activity of the active coumarin metabolites.

African Herbal Remedies with Antioxidant Activity: A Potential Resource Base for Wound Treatment

The use of traditional herbal remedies as alternative medicine plays an important role in Africa since it forms part of primary health care for treatment of various medical conditions, including wounds. Although physiological levels of free radicals are essential to the healing process, they are known to partly contribute to wound chronicity when in excess. Consequently, antioxidant therapy has been shown to facilitate healing of such wounds. Also, a growing body of evidence suggests that, at least, part of the therapeutic value of herbals may be explained by their antioxidant activity. This paper reviews African herbal remedies with antioxidant activity with the aim of indicating potential resources for wound treatment. Firstly, herbals with identified antioxidant compounds and, secondly, herbals with proven antioxidant activity, but where the compound(s) responsible for the activity has not yet been identified, are listed. In the latter case it has been attempted to ascribe the activity to a compound known to be present in the plant family and/or species, where related activity has previously been documented for another genus of the species. Also, the tests employed to assess antioxidant activity and the potential caveats thereof during assessment are briefly commented on.

Potential of essential oils for poultry and pigs

The increasing pressure of abolishing and/or decreasing the use of antibiotics as antimicrobial growth promoters for livestock calls for alternative solutions to sustain the efficiency of current livestock production. Among the alternatives, essential oils have a great potential and are generally considered natural, less toxic, and free from residues. Essential oils have been proven in numerous in vitro studies to exert antimicrobial effects on various pathogens. The current review touched on the basics of essential oils, and the in vivo effects of essential oils on growth, intestinal microflora, anti-oxidation, immune functionality, meat qualities as well as the possible modes of action in poultry and pigs, and the future research areas were proposed.

Antimicrobial interactions of Khoi-San poly-herbal remedies with emphasis on the combination; Agathosma crenulata, Dodonaea viscosa and Eucalyptus globulus

ETHNOPHARMACOLOGICAL RELEVANCE

Plants are often combined in traditional herbal remedies to increase medicinal efficacy, thus this investigation provides some insight into the antimicrobial efficacies of selected combinations.

AIMS OF THE STUDY

The first aim was to scientifically validate antibacterial efficacy of plant mixtures that are traded within peri-urban centres of Cape Town (Western Cape, South Africa). This was followed by an in-depth evaluation of the most antimicrobially active mixture; Agathosma crenulata, Dodonaea viscosa with Eucalyptus globulus.

MATERIALS AND METHODS

Methanol and aqueous extracts of six plant mixtures were screened for antibacterial properties against two Gram-negative and two Gram-positive bacteria using the minimum inhibitory microdilution method. Thereafter, chloroform: methanol (1:1; v/v) extracts, essential oils and aqueous extracts of Agathosma crenulata, Dodonaea viscosa and Eucalyptus globulus were assayed for antimicrobial activity independently and in various combinations. The fractional inhibitory concentration indices (ƩFIC) were determined for double and triple plant combinations to establish antimicrobial interactions.

RESULTS

From the six plant mixtures prepared by herbalists, a methanol extract derived from combining Agathosma crenulata, Dodonaea viscosa and Eucalyptus globulus showed the best antibacterial activity. The MIC values of 49μg/ml for Staphylococcus aureus and Bacillus subtilis, and 98μg/ml for Klebsiella pneumoniae and Escherichia coli were recorded. When Agathosma crenulata, Dodonaea viscosa and Eucalyptus globulus were mixed in various 1:1 combinations, mostly additive and synergistic interactions were noted. The most noteworthy synergistic (ΣFIC value 0.07) 1:1 combinations were observed for the chloroform: methanol extracts of Agathosma crenulata mixed with Eucalyptus globulus against Klebsiella pneumoniae, Staphylococcus aureus and Bacillus subtilis. When combined in a mixture of three plants (1:1:1), enhanced efficacy was evident against most of the pathogens, for both organic and aqueous extracts. The triple combination against Bacillus subtilis demonstrated the greatest synergy (ΣFIC values of 0.03).

CONCLUSIONS

The enhanced antimicrobial efficacy and synergistic interactions noted for some of the mixtures, particularly the combination of Agathosma crenulata, Dodonaea viscosa and Eucalyptus globulus support the Western Cape Khoi-San traditional medicinal practices of combining plants for enhanced efficacy.

Commercially Important Medicinal Plants of South Africa: A Review

There is a growing interest in natural plant-based remedies as a source for commercial products. Around 80% of the South African population use traditional medicines to meet their primary health care needs; however, only a few South African medicinal plants have been exploited to their full potential in terms of commercialization. The opportunity for bioprospecting of plant compounds for novel pharmaceuticals remains largely untapped. Certain renowned medicinal plants of international acclaim including buchu and rooibos are currently contributing to local enterprise; however, other exciting opportunities exist for commonly used plants which have not yet reached the international arena. This paper focuses on the key research and development contributions of 10 commercially important medicinal plants of South Africa. Traditional uses, scientific validation, commercialisation developments, as well as both potential opportunities and setbacks are discussed.

Potential of Complementary and Alternative Medicine in Preventive Management of Novel H1N1 Flu (Swine Flu) Pandemic: Thwarting Potential Disasters in the Bud

The emergence of novel H1N1 has posed a situation that warrants urgent global attention. Though antiviral drugs are available in mainstream medicine for treating symptoms of swine flu, currently there is no preventive medicine available. Even when available, they would be in short supply and ineffective in a pandemic situation, for treating the masses worldwide. Besides the development of drug resistance, emergence of mutant strains of the virus, emergence of a more virulent strain, prohibitive costs of available drugs, time lag between vaccine developments, and mass casualties would pose difficult problems. In view of this, complementary and alternative medicine (CAM) offers a plethora of interesting preventive possibilities in patients. Herbs exhibit a diverse array of biological activities and can be effectively harnessed for managing pandemic flu. Potentially active herbs can serve as effective anti influenza agents. The role of CAM for managing novel H1N1 flu and the mode of action of these botanicals is presented here in an evidence-based approach that can be followed to establish their potential use in the management of influenza pandemics. The complementary and alternative medicine approach deliberated in the paper should also be useful in treating the patients with serious influenza in non pandemic situations.

Evidence of symbiosis between the soil yeast Cryptococcus laurentii and a sclerophyllous medicinal shrub, Agathosma betulina (Berg.) Pillans

The interaction between a common soil yeast, Cryptococcus laurentii, and a slow-growing medicinal plant adapted to low-nutrient soils, Agathosma betulina (Berg.) Pillans, was studied. C. laurentii CAB 578 was isolated from the rhizosphere of wild A. betulina, and liquid chromatography-tandem mass spectrometry (LC-MS-MS) analysis revealed that the yeast was capable of producing polyamines, such as cadaverine and spermine, while growing in vitro in a chemically defined medium. Since the exogenous application of polyamines are known to impact on root growth, these findings supported the results obtained when axenic cultures of A. betulina seedlings were inoculated with C. laurentii CAB 578 and cultivated for 5 months under glasshouse conditions. The presence of the yeast increased root growth by 51%. Using soil dilution plates, it was demonstrated that yeast numbers were greater in the vicinity of the roots than in the bulk soil. In addition, fluoromicroscopy, in combination with the fluorescent probes Fungolight and Calcofluor white, revealed the presence of metabolic active yeast colonies on the rhizoplane 5 months after initiation of the experimentation. The study provided evidence for a symbiosis between C. laurentii and A. betulina.

A broad review of commercially important southern African medicinal plants

AIMS OF THE STUDY

Commercially important indigenous medicinal plants of southern Africa are reviewed in the context of fundamental knowledge about their ethnobotany, phylogeny, genetics, taxonomy, biochemistry, chemical variation, reproductive biology and horticulture. The aim is to explore the rapidly increasing number of scientific publications and to investigate the need for further research.

MATERIALS AND METHODS

The Scopus (Elsevier) reference system was used to investigate trends in the number of scientific publications and patents in 38 medicinal plant species. Fifteen species of special commercial interest were chosen for more detailed reviews: Agathosma betulina, Aloe ferox, Artemisia afra, Aspalathus linearis, Cyclopia genistoides, Harpagophytum procumbens, Hoodia gordonii, Hypoxis hemerocallidea, Lippia javanica, Mesembryanthemum tortuosum, Pelargonium sidoides, Siphonochilus aethiopicus, Sutherlandia frutescens, Warburgia salutaris and Xysmalobium undulatum.

RESULTS

In recent years there has been an upsurge in research and development of new medicinal products and new medicinal crops, as is shown by a rapid increase in the number of scientific publications and patents. Despite the fact that an estimated 10% of the plant species of the world is found in southern Africa, only a few have been fully commercialized and basic scientific information is often not available.

CONCLUSIONS

The limited available information indicates that some of the plants display remarkable regional variation in morphological, genetic and chemical characters that should be more thoroughly investigated. Basic biological information is needed to guide the rapidly accelerating commercialization process, especially the selection of superior clones, the development of new cultivars and the standardization of raw materials.

Antimicrobial activity of South African medicinal plants

This paper reviews the antimicrobial research undertaken on South African medicinal plants during the period 1997-2008. Antimicrobial methods (disc diffusion, minimum inhibitory concentration (MIC), bio-autography) are briefly discussed and an analysis of the publications reviewed indicates that the majority of papers use MIC assays for antimicrobial determination. Antimicrobial investigations on extracts are presented where the most active plants are identified from screening publications. A summary of some bioactive compounds are given with data restricted to papers reporting quantitative antimicrobial activity equivalent to or below 200 microg/ml. Antimicrobial activities on the essential oils of indigenous medicinal aromatic plants are also reviewed. An overview is given on what activities (extracts, compounds and oils) should be considered noteworthy for publication. Studies focusing on geographical ethnobotany, specific pathogenesis, formulation aspects and in vivo investigations are examined. Future recommendations to consider include pathogen selection, interactive studies and dosage administrations.

Spasmolytic action of Lepechinia caulescens is through calcium channel blockade and NO release

The present study was undertaken to elucidate the mode of action of methanol extract from aerial parts of L. caulescens (TC-MELc) as spasmolytic agent on in vitro rat ileum test, and investigate the possible antibacterial activity of different extracts from the plant. TC-MELc induced a concentration-dependent (0.001 to 100microg/mL) antispasmodic effect on spontaneous contractions. TC-MELc also (IC50 11.2microg/mL) induced a marked depression on cumulative concentration-response curve for carbachol (Emax=2.3+/-0.3g vs. 0.66+/-0.1g) and serotonin (Emax=1.1+/-0.3g vs. -0.01+/-0.09g). Besides, extract decreased and displaced to the right KCl and CaCl2 concentration-response curves. Moreover, TC-MELc (11.2microg/mL) provoked a total relaxation when ileum strips were contracted with carbachol (1microM) in calcium-free Krebs solution. Pre-treatment with l-NAME (10microM) produced a significant change of the relaxant response and activity was markedly inhibited. Additionally, hexanic (HELc), dichloromethanic (DELc) and methanolic (MELc) extracts from aerial parts were studied to determine their antibacterial activity. DELc showed antibacterial activity on all bacterial strains assayed (<or=100.0microg/mL). Data indicate that L. caulescens contains antibacterial and spasmolytic constituents mediating their effect through blockade of Ca2+ influx and NO release, which may explain its traditional use against diarrhoea.

Studies on antibacterial, anti-inflammatory and antioxidant activity of herbal remedies used in the treatment of benign prostatic hyperplasia and prostatitis

Crude water and ethanolic extracts of five herbal remedies reported in the literature for traditional treatment of benign prostatic hyperplasia (BPH) and/or prostatitis were investigated for their effect on hydroxyl scavenging activity, antibacterial activity and their ability to inhibit cyclooxygenase-1 and -2 (COX-1 and COX-2) catalysed prostaglandin biosynthesis. Both the water and ethanol extracts of Hypoxis hemerocallidea and Epilobium parviflorum inhibited the growth of Escherichia coli. All 10 extracts scavenged the hydroxyl radical but with various potencies (32-93%). Ethanolic extracts were the most active in inhibiting COX-1 catalysed prostaglandin biosynthesis. The ethanolic extract of Epilobium parviflorum showed inhibitory effects on both the COX-1 and -2 catalysed prostaglandin biosynthesis, inhibited growth of Escherichia coli and exerted antioxidant activity. Although these results support the traditional use of Epilobium parviflorum for treatment of prostatitis and BPH, further investigation is required, for this promising plant.

Antioxidant and genotoxic properties of South African herbal extracts

This study investigated the antioxidant and genotoxic properties of 13 South African herbal extracts. Results from the single-cell gel electrophoresis (Comet) assay indicated that there were profound differences between the plant extracts in their ability to produce DNA damage, which varied from highly genotoxic to protective. Similarly, water and methanol extracts of all the herbal preparations showed variable potencies in scavenging hydroxyl radicals, as measured by means of electron spin resonance spectrometery (ESR) with the spin trap alpha-phenyl-N-tert-butylnitrone (PBN). In general, methanol extracts were better scavengers of hydroxyl radicals than the corresponding water extracts. This was also true of the ability of these extracts to inhibit membrane lipid peroxidation, assessed with diphenyl-1-pyrenylphosphine (DPPP). However, neither methanol nor water extracts had the ability to protect against DNA damage. The results show that further research on South African traditional herbal extracts is imperative to gain understanding of the mechanisms involved in their pharmacological effects. The tests implemented in the present investigation are recommended for screening other herbal extracts.