F.R. Van Heerden

Hoodia gordonii: a natural appetite suppressant.

AIMS OF THE STUDY Several species of the stapeliads, a group of stem succulents belonging to the family Apocynaceae are reported on in the ethnopharmacology literature and many of the references relate to their use as food plants. The most important of these plants is Hoodia gordonii, which during the past decade has risen from an almost forgotten spiny, desert plant to an important commercial appetite-suppressant herbal. The aim of this review is to summarize the botany, ethnopharmacology and phytochemistry of Hoodia gordonii. MATERIALS AND METHODS Journal articles and books were used to collect information on Hoodia gordonii and related species. RESULTS Many books and articles documented the use of stapeliad species as food plants and earlier references refer to the use Hoodia species as a thirst quencher. However, prior to the publication of the patent application, only a single reference referring to the use of Hoodia pilifera as appetite suppressant was found. The structures of several steroid glycosides isolated from Hoodia gordonii are summarized. CONCLUSIONS Hoodia gordonii illustrates how a combination of ethnobotany and scientific research can lead to a commercial product which can greatly benefit the indigenous people.

South African Helichrysum species : A review of the traditional uses, biological activity and phytochemistry

AIMS OF THE STUDY In South Africa, the genus Helichrysum is widely used in traditional medicine. The uses are well documented although renaming of species and the resulting confusing taxonomic nomenclature may cause uncertainty as to which specific species was referred to in some reports. The aim of this paper is to present a collated and coherent overview of the documented traditional uses of Helichrysum species and to update the botanical identity of previously studied species. MATERIALS AND METHODS Databases (Scifinder, ISI Web of Knowledge) and several books were used to collect in information on South African Helichrysum species. RESULTS The traditional uses, chemistry and biological activity of Helichrysum species have been summarized. It was attempted to give clarity as to exactly which species is refer to in the ethnobotanical literature. CONCLUSIONS Although a large number of ethnopharmacological uses have been documented and the chemistry of the genus has been studied extensively, only a few South African species have been investigated for their biological activity.

Phytochemistry and in vitro pharmacological activities of South African Vitex (Verbenaceae) species

AIM OF THE STUDY The in vitro phytochemical and pharmacological investigation of the non-volatile extracts of five South African Vitex species (Verbenaceae); V. obovata ssp. obovata, V. obovata ssp. wilmsii, V. pooara, V. rehmannii and V. zeyheri were investigated in order to validate their traditional use to treat a wide range of ailments such as malaria, wounds, skin diseases and body pains. MATERIAL AND METHODS The antimicrobial activity was assessed using the minimum inhibitory concentration assay. Through bioactivity-guided fractionation, the fraction responsible for the antimicrobial activity was determined. The toxicity profile, anti-oxidant and anti-inflammatory activity was evaluated using the tetrazolium cellular viability, 2,2-diphenyl-1-picrylhydrazyl and 5-lipoxygenase assays respectively. The antimalarial activity of the extracts and isolated compound from V. rehmannii was also investigated on the chloroquine-resistant Gambian FCR-3 strain of Plasmodium falciparum using the tritiated hypoxanthine incorporation assay. RESULTS Mostly good antimicrobial inhibition was evident against Gram-positive bacteria (0.02-8.00 mg/ml) and lower activity against the Gram-negative bacteria and the yeast (0.50-8.00 mg/ml). The fraction responsible for antimicrobial activity of V. rehmannii was purified to give a labdane diterpene as an inseparable epimeric mixture of 12S,16S/R-dihydroxy-ent-labda-7,13-dien-15,16-olide. Cirsimaritin was also isolated and identified from V. rehmannii. All the species, apart from V. zeyheri, exhibited scavenging activity (IC50: 22.14+/-1.74 to 33.06+/-1.68 microg/ml) in the anti-oxidant assay. None of the species displayed any anti-inflammatory activity at 100 microg/ml. All the extracts and the labdane diterpene exhibited good antimalarial activity, with the labdane diterpene being the most active (IC50: 2.39+/-0.64 microg/ml). The test extracts were shown to be highly toxic, displaying safety index values ranging from 0.53 to 2.59. CONCLUSION Of all the pharmacological investigations, the antimalarial and antimicrobial activity exhibited greatest activity and may provide a scientific basis for the ethnomedical use of Vitex species.

In vitro biological activities of niloticane, a new bioactive cassane diterpene from the bark of Acacia nilotica subsp. kraussiana

ETHNOPHARMACOLOGICAL RELEVANCE Acacia nilotica subsp. kraussiana was reported in African traditional medicine for the treatment of various ailments. Isolation of an active compound in this study from the bark extract may lead to the validation of its efficiency as a traditional crude drug. AIMS OF THE STUDY This study aimed to isolate active compound(s) from an ethyl acetate bark extract of Acacia nilotica subsp. kraussiana and to investigate some of its biological activity. MATERIALS AND METHODS The isolation process was carried out using bioassay-guided fractionation. The isolated compound was tested for antibacterial activity using the micro-dilution assay; anti-inflammatory activity using the COX-1 and COX-2 assays and investigated for inhibitory effect against acetylcholinesterase using the microplate assay. RESULTS A new bioactive compound was isolated and identified as a cassane diterpene, niloticane. Niloticane showed antibacterial activity against Gram-positive bacteria Bacillus subtilis and Staphylococcus aureus with MIC values of 4 and 8microg/mL, respectively. With Gram-negative bacteria, niloticane showed weak activity. MIC values obtained were 16 and 33microg/mL against Klebsiella pneumonia and Escherichia coli, respectively. In the cyclooxygenase test, niloticane possessed activity with IC50 values of 28 and 210microM against COX-1 and COX-2, respectively. IC50 values observed with indomethacin (positive control) were 3.6microM for COX-1 and 189microM for COX-2. In the acetylcholinesterase test, niloticane showed anti-cholinesterase activity with an IC50 value of 4microM. IC50 values obtained by the galanthamine (positive control) was 2.0microM. CONCLUSION The results obtained support the traditional uses of the bark of Acacia nilotica subsp. kraussiana in African traditional medicine for the treatment of some ailments that relate to microbial diseases, inflammation and central nervous system disorders.

Antibacterial Activity of Flavonoids from the Stem Bark of Erythrina caffra Thunb.

The antibacterial activity of the stem bark of Erythrina caffra Thunb. was investigated against different bacterial strains. The antibacterial activity was determined by a micro broth dilution assay. Antibacterial compounds were isolated and identified using a Bruker Avance III LPO NMR spectrometer. Four known flavonoids, abyssione‐V 4′‐O‐methyl ether, 6,8‐diprenylgenistein, alpinumisoflavone and burttinone, were isolated. All the compounds were active against both Gram‐negative and Gram‐positive bacteria. The minimum inhibitory concentration values obtained (MIC) ranged from 3.9 μg/mL to 125 μg/mL. This is the first report of antibacterial activity of burttinone and the isolation of these compounds from E. caffra. Copyright

Identification of compounds with cytotoxic activity from the leaf of the Nigerian medicinal plant, Anacardium occidentale L. (Anacardiaceae)

Cancer is now the second-leading cause of mortality and morbidity, behind only heart disease, necessitating urgent development of (chemo)therapeutic interventions to stem the growing burden of cancer cases and cancer death. Plants represent a credible source of promising drug leads in this regard, with a long history of proven use in the indigenous treatment of cancer. This study therefore investigated Anacardium occidentale, one of the plants in a Nigerian Traditional Medicine formulation commonly used to manage cancerous diseases, for cytotoxic activity. Bioassay-guided fractionation, spectroscopy, Alamar blue fluorescence-based viability assay in cultured HeLa cells and microscopy were used. Four compounds, zoapatanolide A (1), agathisflavone (2), 1,2-bis(2,6-dimethoxy-4-methoxycarbonylphenyl)ethane (anacardicin, 3) and methyl gallate (4), were isolated, with the most potent being zoapatanolide A with an IC50 value of 36.2±9.8µM in the viability assay. To gain an insight into the likely molecular basis of their observed cytotoxic effects, Autodock Vina binding free energies of each of the isolated compounds with seven molecular targets implicated in cancer development (MAPK8, MAPK10, MAP3K12, MAPK3, MAPK1, MAPK7 and VEGF), were calculated. Pearson correlation coefficients were obtained with experimentally-determined IC50 in the Alamar blue viability assay. While these compounds were not as potent as a standard anticancer compound, doxorubicin, the results provide reasonable evidence that the plant species contains compounds with cytotoxic activity. This study provides some evidence of why this plant is used ethnobotanically in anticancer herbal formulations and justifies investigating Nigerian medicinal plants highlighted in recent ethnobotanical surveys.

Kaempferol, a mutagenic flavonol from Helichrysum simillimum:

Helichrysum simillimum is native to South Africa. It is used for the treatment of coughs, colds, fever, infections, headache, and menstrual pain. Extracts of this species showed mutagenic effects in the Salmonella/microsome assay. The aim of this study was to isolate and determine the mutagenic constituents of H. simillimum. Bioassay-guided fractionation of 90% aqueous methanol extracts, using Salmonella typhimurium TA98, led to the isolation of the flavonol kaempferol.

Dehydro-brachylaenolide: an eudesmane-type sesquiterpene lactone.

The three-ring eudesmanolide, C15H16O3, is a natural product isolated from Dicoma anomala Sond. (Asteraceae). The compound contains an endo–exo cross conjugated methylenecyclohexenone ring with an envelope conformation trans-fused with cyclohexane and trans-annelated with an α-methylene γ-lactone. The absolute structure was assigned by optical rotation measurements compared to those from the synthetic compound with known stereochemistry. The crystal packing is consolidated by C—H⋯O interactions.