The additive and synergistic antimicrobial effects of select frankincense and myrrh oils--a combination from the pharaonic pharmacopoeia.

AIMS: The in vitro antimicrobial activity of three essential oil samples of frankincense (Boswellia rivae, Boswellia neglecta and Boswellia papyrifera) and two essential oil samples of myrrh and sweet myrrh (Commiphora guidotti and Commiphora myrrha), collected from different regions of Ethiopia, was investigated independently and in combination to determine their anti-infective properties. METHODS AND RESULTS: The microdilution minimum inhibitory concentration (MIC) assay was performed, whereby it was noted that generally Cryptococcus neoformans (MIC values in the range of 0·8-1·4 mg ml(-1)) and Pseudomonas aeruginosa (MIC values in the range of 0·5-1·3 mg ml(-1)) often appeared to be the most susceptible micro-organisms against oils of both Boswellia and Commiphora spp. When assayed in various combinations, the frankincense and myrrh oils displayed synergistic, additive and noninteractive properties, with no antagonism noted. When investigating different ratio combinations against Bacillus cereus, the most favourable combination was between B. papyrifera and C. myrrha. The composition of the oils was determined by gas chromatography coupled to mass spectrometry (GC-MS) to document the specific chemotypes used in the study, and the chemical profiles were found to be congruent with previously reported data. CONCLUSIONS: The majority of interactions identified synergistic and additive effects, with strong synergism noted between B. papyrifera and C. myrrha. SIGNIFICANCE AND IMPACT OF THE STUDY: Frankincense and myrrh essential oils have been used in combination since 1500 bc; however, no antimicrobial investigations have been undertaken to confirm their effect in combination. This study validates the enhanced efficacy when used in combination against a selection of pathogens.

Prooxidant action of knipholone anthrone: copper dependent reactive oxygen species generation and DNA damage.

Knipholone (KP) and knipholone anthrone (KA) are natural 4-phenylanthraquinone structural analogues with established differential biological activities including in vitro antioxidant and cytotoxic properties. By using DNA damage as an experimental model, the comparative Cu(II)-dependent prooxidant action of these two compounds were studied. In the presence of Cu(II) ions, the antioxidant KA (3.1-200 microM) but not KP (6-384 microM) caused a concentration-dependent pBR322 plasmid DNA strand scission. The DNA damage induced by KA could be abolished by reactive oxygen species scavengers, glutathione and catalase as well as EDTA and a specific Cu(I) chelator bathocuproine disulfonic acid. In addition to Cu(II) chelating activity, KA readily reduces Cu(II) to Cu(I). Copper-dependent generation of reactive oxygen species and the subsequent macromolecular damage may be involved in the antimicrobial and cytotoxic activity of KA.

In vivo antimalarial activity of essential oils from Cymbopogon citratus and Ocimum gratissimum on mice infected with Plasmodium berghei.

The essential oils obtained by hydrodistillation from fresh leaves of Cymbopogon citratus and Ocimum gratissimum growing in Cameroon were analyzed by GC and GC/MS. The main constituents of the oil of Ocimum gratissimum were gamma-terpinene (21.9 %), beta-phellandrene (21.1 %), limonene (11.4 %) and thymol (11.2 %), while the oil of Cymbopogon citratus contained geranial (32.8 %), neral (29.0 %), myrcene (16.2 %) and beta-pinene (10.5 %). The effects of these oils on the growth of Plasmodium berghei were investigated. Both oils showed significant antimalarial activities in the four-day suppressive in vivo test in mice. At concentrations of 200, 300 and 500 mg/kg of mouse per day, the essential oil of C. citratus produced the highest activity with the respective percentages of suppression of parasitaemia: 62.1 %, 81.7 % and 86.6 %. The corresponding values for the oil of O. gratissimum at the same concentrations were 55.0 %, 75.2 % and 77.8 %, respectively. Chloroquine (10 mg/kg of mouse, positive control) had a suppressive activity of 100 %.

Sesquiterpene lactone and friedelane derivative from drypetes molunduana.

A new sesquiterpene lactone, drypemolundein A and a new friedelane derivative, drypemolundein B, along with seven known compounds have been isolated from the whole stems of Drypetes molunduana Pax and Hoffm. Their structures were established on the basis of one- and two-dimensional NMR, homo- and hetero-nuclear spectroscopic evidence.

Chromones and anthrones from Aloe marlothii and Aloe rupestris.

A phytochemical investigation of the leaf exudate of Aloe marlothii has resulted in the isolation of a new chromone (7-O-methylaloeresin A) and a new anthrone (5-hydroxyaloin A 6'-O-acetate). Furthermore 7-O-methylaloesin was isolated as a natural product for the first time from the leaf exudate of Aloe rupestris. The structure elucidation of these compounds was based on spectral data including 2D NMR. The chemotaxonomic value of 7-O-methylaloesin in Aloe series Asperifoliae and section Pachydendron is discussed.

Ethnomedical aspects of the commonly used toothbrush sticks in Ethiopia.

OBJECTIVE: To determine the botanical identity, cytotoxicity, and antibacterial property of the commonly used toothbrush sticks in Ethiopia. SETTING: Research laboratories of the departments of Biology and Chemistry, Addis Ababa University between December 1993 and May 1995. METHODS: The study was performed by purchasing the commonly used toothbrush sticks from street markets in various towns of Ethiopia. Voucher specimens were collected and their botanical identity was determined following floral keys. The toothbrush sticks were ground in a mill and soaked in absolute methanol for 24 hours and filtered. The filtrates were dried in a rotary evaporator and the crude extracts were stored at 4 degrees C. The crude methanol extracts were used to test their antibacterial activity by impregnating into filter paper discs and placing on test plates of Staphylococcus aureus and Bacillus cerues. Their lethality to brine shrimp (Artemia salina) was performed following standard procedures. RESULTS: Twenty different species of plant used as toothbrush were collected and their botanical identity determined. Crude methanol extracts of only Agave sisalana, Birbira and Hypericum revolutum test concentrations up to 500 micrograms/ml showed weak toxicity to brine shrimp. All the extracts showed antibacterial activity against Staphylococcus aureus and Bacillus cereus by agar diffusion method. CONCLUSION: Toothbrush sticks can be used by the vast majority of people who cannot afford buying the commercial toothbrush and toothpaste. The toothbrush sticks may be important for the oral and dental hygiene of the users and hence may be useful in decreasing dental caries. Further studies should focus on the effect of the toothbrush sticks against other common bacteria that are associated with dental diseases.

10-Hydroxyaloin B 6'-O-Acetate, an Oxanthrone from Aloe claviflora

Analysis of the leaf exudate of Aloe claviflora resulted in the isolation of a new oxanthrone, 10-hydroxyaloin B 6'-O-acetate (1), whose structure was determined on the basis of spectral evidence as well as by conversion to the known compound 10-hydroxyaloin B (2).

Limonoids showing selective toxicity to DNA repair-deficient yeast and other constituents of Trichilia emetica.

Bioactivity-directed fractionation of the MeCOEt extract of Trichilia emetica (Meliaceae) resulted in the isolation of the limonoids nymania 1 (1), drageana 4 (3), trichilin A (4), rohituka 3 (5), and Tr-B (7) and the novel seco-A protolimonoid 8. Of these, nymania 1 and Tr-B showed selective inhibitory activity toward DNA repair-deficient yeast mutants. The isolation, structure elucidation, 13C NMR spectral assignments, and biological activities of these compounds are reported.

Three dihydroanthracenones from Gasteria bicolor.

The stem and leaves of Gasteria bicolor afforded three new dihydroanthracenones namely 3,4-dihydro-2,6,9-trihydroxy-8-methyl-1(2H)-anthracenone (gasteriacenone A), 3,4-dihydro-2,4,9-trihydroxy-6-methoxy-8-methyl-1(2H)-anthracenone (gasteriacenone B) and 3,4-dihydro-4,6,9-trihydroxy-7-carbomethoxy-8-methyl-1(2H)-anthraceno ne (gasteriacenone C). Their structures were determined by spectroscopic methods including 2D NMR techniques.

Nematicidal activities of two phytoalexins from Taverniera abyssinica.

The traditional analgesic and antipyretic Ethiopian drug "Dingetegna" is made of dried root material of Taverniera abyssinica A. Rich (Leguminosae). In a screening for nematicidal natural products, "Dingetegna" extracts showed strong nematicidal activities towards C. elegans. In the following, medicarpin and 4-hydroxymedicarpin were isolated as nematicidal constituents from the extracts. In a microwell plate assay for nematicidal activity, both compounds exhibited an LD50 of 25 micrograms/ml towards C. elegans. Beside these nematicidal effects, weak cytotoxic and antimicrobial activities were observed. In addition, both compounds inhibited oxygen consumption of axenically grown C. elegans, L 1210 cells, and filamentous fungi. Respiration in sensitive bacteria was not affected. In L 1210 cells, the incorporation of precursors into macromolecules was affected in the presence of glucose, indicating that inhibition of respiration is not the only target site of the compounds.

Antiulcerative properties and acute toxicity profile of some African medicinal plant extracts.

The aqueous extract of the stem bark of Tetrapleura tetraptera Schum et Thonn., Guibourtia ehie Leonard and the root extract of Taverniera abyssinica A. Rich. were used for the treatment of gastrointestinal related clinical problems in African ethnomedicine. HCl/EtOH-induced ulceration was used in fasted rat stomach to investigate the anti-ulcerative properties of the extracts. The acute cytotoxicity of the extracts using brine shrimp larvae was also investigated. The aqueous extracts of Tav. abyssinica (250-500 mg/kg), Tet. tetraptera (500-1000 mg/kg), G. ehie (500-1000 mg/kg) and a combination of Tet. tetraptera and G. ehie (1:4) (500-1000 mg/kg) produced significant (P < 0.05) inhibition (54-80%, 86-98%, 48-80% and 54-92%, respectively) of the HCl/EtOH-induced ulceration of the stomach compared with controls. The acute cytotoxic concentrations of the extracts which killed 50% (LC50) of brine shrimp within 24 h was 438 micrograms/ml for Tet. tetraptera, 220 micrograms/ml for the 1:4 combination of Tet. tetraptera and G. ehie and 1409 micrograms/ml for Tav. abyssinica. None of the shrimp were killed by G. ehie, even at 2 mg/ml.

Two bioactive pterocarpans from Erythrina burana.

Bioactivity-directed fractionation of the CHCl3 extract of the bark of Erythrina burana afforded phaseollidin [1] and cristacarpin [2]. Both 1 and 2 exhibited moderate but selective activity towards DNA repair-deficient yeast mutants, whereas only 1 was found to be cytotoxic. 13C-nmr spectra of both compounds were assigned.

Preliminary studies on antipyretic and analgesic properties of Taverniera abyssinica.

In an attempt to ascertain the pharmacological basis of the use of the marketed traditional drug Taverniera abyssinica A. Rich. (Amharic name Dingetegna), crude extracts as well as purified substances of this plant were tested for their antipyretic and analgesic properties. Antipyretic activity was determined on rats made hyperthermic by yeast injection and analgesic activity was determined by the hot plate, as well as the acetic acid induced writhing, methods. The study showed that the plant possesses significant antipyretic and analgesic activities.

Intestinal smooth muscle spasmolytic actions of the aqueous extract of the roots of Taverniera abyssinica.

A room temperature aqueous extract of the roots of Taverniera abyssinica antagonized the contractile responses of the guinea-pig ileum to acetylcholine and histamine. The extract also relaxed the smooth muscle of the rabbit duodenum, abolished the pendular contractions and antagonized the effects of acetylcholine and histamine on this tissue. The results confirm that there may be a sound pharmacological basis for the ethnomedical use of the roots of this plant to treat stomach ache.

Aloe-Emodin Acetate, an Anthraquinone Derivative from Leaves of Kniphofia foliosa.

The leaves of K. FOLIOSA yielded aloe-emodin acetate in addition to chrysophanol and knipholone. Aloe-emodin acetate is reported here in Liliaceae family for the first time.