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.

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.

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.

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.

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.

Dehydro-brachylaenolide: an eudesmane-type sesquiterpene lactone.

The three-ring eudesmanolide, C(15)H(16)O(3), is a natural product isolated from Dicoma anomala Sond. (Asteraceae). The compound contains an endo-exo cross conjugated methyl-enecyclo-hexenone ring with an envelope conformation trans-fused with cyclo-hexane and trans-annelated with an α-methyl-ene 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.

Securidacaxanthone A, a heptaoxygenated xanthone from Securidaca longepedunculata.

From the root bark of Securidaca longepedunculata, a heptaoxygenated xanthone (1) has been isolated as well as two known xanthones (2) and (3) and two salicylic acid derivatives (4) and (5). The structure of 1 has been elucidated from 1H and 13C-NMR spectral data.

Identification of atractyloside by LC-ESI-MS in alleged herbal poisonings.

An LC-MS screening method was developed to detect the presence of atractyloside (ATR), the toxic principle of a commonly used medicinal plant in South Africa, Callilepis laureola, in biological matrices such as body fluids and human viscera.

Fatal Datura poisoning: identification of atropine and scopolamine by high performance liquid chromatography/photodiode array/mass spectrometry.

A forensic method comprising solid phase extraction and HPLC analysis was developed for the detection and confirmation of atropine and scopolamine, the main toxic alkaloids of Datura stramonium and Datura ferox. This method allowed the direct coupling of an electrospray (ZMD) mass selective detector to the HPLC system. Under these conditions, atropine and scopolamine were well separated from other components and detected on the PDA (LOD = 1 microg/ml) and ZMD (LOD(atropine) = 10 pg/ml; LOD(scopolamine) = 100 pg/ml) detectors. Four geographically isolated populations of each of D. stramonium and D. ferox were analysed for seed alkaloids and it was found that the two species were diagnostically different in their atropine-scopolamine ratios. The optimised HPLC method was used to analyse three viscera samples of an adult Caucasian male whose death was ascribed to a fatal heart attack. Atropine and scopolamine were detected in the stomach and its contents, which contained Datura seeds. The chemical profile of the seeds found in the stomach contents was similar to those from four geographically different D. ferox plants.

Scaphopetalone and scaphopetalumate, a lignan and a triterpene ester from Scaphopetalum thonneri.

From the methanol extract of the stem bark of Scaphopetalum thonneri, two new compounds, including one lignan, named scaphopetalone, one new ester of ferulic acid, named scaphopetalumate were isolated together with three known compounds including: two coumarins (scopoletin and scopolin), and one pentacyclic triterpene (oleanolic acid). The structure of the new compounds were elucidated by means of spectroscopic analyses.

Accidental fatal poisoning by Nicotiana glauca: identification of anabasine by high performance liquid chromatography/photodiode array/mass spectrometry.

A method, based on reversed phase high performance liquid chromatography (HPLC) was developed for the detection and quantification of anabasine, the toxic alkaloid of Nicotiana glauca, in forensic applications. A standard solid phase extraction (SPE) method was used for the extraction of anabasine from viscera, but was optimized for the extraction of this alkaloid from plant material. The careful selection of mobile phase components allowed the direct coupling of electron impact (EI) and Z spray mass selective detector (ZMD) of the HPLC. Under these conditions, anabasine was well separated from nicotine and could be detected on the PDA (limit of detection, LOD = 250 ng/ml), TMD (LOD = 10 microg/ml) and ZMD (LOD =1 ng/ml) detectors. Three geographically isolated N. glauca trees were analyzed for alkaloid content and it was found that both the leaves and the flowers contain anabasine. The optimized HPLC method was used to analyze two viscera samples (the stomach and contents of a mother and child who putatively died from food poisoning) and a flower exhibit. Anabasine was detected in both the viscera samples, supporting the finding that these fatalities were due to the ingestion of N. glauca accidentally collected with traditional spinach (marog). The alkaloid profile of the flower exhibit submitted with the viscera samples was similar to those obtained from flowers collected from three different N. glauca trees. The results show that anabasine and/or N. glauca poisoning can easily be confirmed using the forensic methodology described.

Cytotoxic isoflavones from Erythrina indica.

Bioassay-directed fractionation of the CH(2)Cl(2)-MeOH (1:1) extract of the stem bark of Erythrina indica, has resulted in the isolation of two new isoflavone derivatives named indicanines D and E together with 11 known compounds including: six isoflavones (genistein, wighteone, alpinumisoflavone, dimethylalpinumisoflavone, 8-prenyl erythrinin C, and erysenegalensein E), one cinnamate (erythrinassinate B), two pentacyclic triterpenes (oleanolic acid and erythrodiol), and two phytosterols (stigmasterol and its 3-O-beta-D-glucopyranoside). The structures of the new compounds were elucidated by means of spectroscopic analysis. The in vitro cytocidal activity against KB cells of some of the isolated compounds is also reported.

Asebotin, a dihydrochalcone glucoside from Guibourtia tessmannii.

Asebotin (1), a dihydrochalcone glucoside, was isolated from the stem bark of Guibourtia tessmanni and characterised by means of spectroscopic analysis including 1H-, 13C, MS and 1D Noe difference experiment.

6'-O-Coumaroylaloesin from Aloe castanea--a taxonomic marker for Aloe section Anguialoe.

The structure of 6'-O-coumaroylaloesin [2-acetonyl-8-(6-O-coumaroyl-beta-D-glucopyranosyl)-7-hydrox y-5-methylchromone], a mono-ester chromone derivative in which only the 6-position of the glucosyl moiety is esterified, was determined by spectroscopic methods. The compound is a unique chemotaxonomic character restricted to the six species in Aloe section Anguialoe.

Indicanine A, a new 3-phenylcoumarin from root bark of Erythrina indica.

A new 3-phenylcoumarin, indicanine A (1), has been isolated from the root bark of the African medicinal plant Erythrina indica, together with three known compounds, robustic acid (2), daidzein, and 8-prenyldaidzein. The structure of the new compound was characterized, as 4-hydroxy-5-methoxy-3-(4'-methoxyphenyl)-2" -(1-methylethenyl)dihydrofurano[4",5":6,7]coumarin by means of extensive spectroscopic analyses. The compounds were found to be devoid of in vitro antibacterial activity.

Indicanines B and C, two isoflavonoid derivatives from the root bark of Erythrina indica.

In addition to two known compounds, 5,4'-di-O-methylalpinumisoflavone and cajanin, a new 3-phenylcoumarin metabolite, named indicanine B, and a new isoflavone derivative, named indicanine C, were isolated from the root bark of Erythrina indica. By means of spectroscopic analysis, the structures of the new compounds were characterized as 4-hydroxy-3-(4'-hydroxyphenyl)-5-methoxy-2",2"-dimethylpyrano [5",6":6,7] coumarin and 4'-hydroxy-5-methoxy-2",2"-dimethylpyrano [5",6":6,7] isoflavone, respectively. The 13C-NMR data of cajanin and the in vitro antimicrobial spectrum and potencies of the isolated compounds are also reported.

The major flavonoid of Dodonaea angustifolia.

The major leaf flavonoid of Dodonaea angustifolia, an important South African traditional medicine, has been identified as 5,7,4'-trihydroxy-3,6-dimethoxyflavone (1).

Synthesis and evaluation of 4-(3-methyl-2-butenoxy) isonitrosoacetophenone, a radiation-induced stress metabolite in Citrus.

The time- and dose-dependent occurrence of 4-(3-methyl-2-butenoxy)isonitrosoacetophenone, a gamma-irradiation-induced stress metabolite was investigated. The chemical synthesis of the compound is reported. The compound exhibits antifungal activity, as well as antioxidant activity, as indicated by its ability to scavenge reactive oxygen radicals in a chemiluminescence assay.

The isolation and identification of some toxic constituents ofAspergillus wentii wehmer.

Extraction of a maize culture of a toxinogenic strain ofA. wentii led to the isolation and characterization of three anthraquinones, three bianthrones, a xanthone and a benzophenone. The structures were derived from spectroscopic data and were supported by chemical degradation. Of these, emodin, 1,6-di-0-methylemodin, 5-0-methylsulochrine and 1,3-di-0-methylemodin bianthrone were mildly toxic to ducklings.