Dulcie A. Mulholland

Analytical Supercritical Fluid Extraction of Natural Products

Supercritical fluid extraction (SFE) is a rapid, selective and convenient method for sample preparation prior to the analysis of compounds in natural product matrices. SFE is usually performed with pure or modified carbon dioxide, which facilitates off-line collection of extracts and on-line coupling with other analytical methods such as gas and supercritical fluid chromatography. A number of factors influence extraction yields, these being solubility of the solute in the fluid, diffusion through the matrix and adsorption processes in the matrix. A wide range of applications is described for the extraction of carotenoids, lipids, flavour and fragrance compounds, steroids and triterpenes, alkaloids and mycotoxins.

Plants traditionally prescribed to treat tazo (malaria) in the eastern region of Madagascar

BackgroundMalaria is known as tazo or tazomoka in local terminology in Madagascar. Within the context of traditional practice, malaria (and/or malaria symptoms) is commonly treated by decoctions or infusions from bitter plants. One possible approach to the identification of new antimalarial drug candidates is to search for compounds that cure or prevent malaria in plants empirically used to treat malaria. Thus, it is worth documenting the ethnobotanical data, and testing the antiplasmodial activity of the extractive from plants.MethodsWe interviewed traditional healers, known locally as ombiasy, at Andasibe in the eastern, rainy part of Madagascar. We recorded details of the preparation and use of plants for medicinal purposes. We extracted five alkaloids from Z. tsihanimposa stem bark, and tested them in vitro against Plasmodium falciparum FCM29.ResultsWe found that traditional healers treat malaria with herbal remedies consisting of one to eight different plants. We identified and listed the medicinal plants commonly used to treat malaria. The plants used included a large number of species from different families. Zanthoxylum sp (Rutaceae) was frequently cited, and plants from this genus are also used to treat malaria in other parts of Madagascar. From the plant list, Zanthoxylum tsihanimposa, bitter plant endemic to Madagascar, was selected and examined. Five alkaloids were isolates from the stem bark of this plant, and tested in vitro against malaria parasite. The geometric mean IC50 values ranged from 98.4 to 332.1 micromolar. The quinoline alkaloid gamma-fagarine exhibited the strongest antiplasmodial activity.ConclusionsThe current use of plants for medicinal purposes reflects the attachment of the Malagasy people to their culture, and also a lack of access to modern medicine. The possible extrapolation of these in vitro findings, obtained with plant extracts, to the treatment of malaria and/or the signs evoking malaria is still unclear. If plants are to be used as sources of novel antimalarial compounds, we need to increase our knowledge of their empirical use to improve plant selection. In the hope of preserving useful resources, we should now gather and record ethnobotanical data in Madagascar, and should try to bridge the gaps between empirics and realism.

Limonoids from Australian members of the Meliaceae

Abstract The seeds of Owenia acidula of Owenia venosa were found to contain a simple limonoid and a derivative of the cyclopropane protolimonoid glabretal, which has also been found in the timber of Aglaia ferruginea . The timber of Toona australis was found to contain cedrelone, and the timber seed of Xylocarpus moluccensis ( sensu Mabberley) have been found to contain a rich mixture of limonoids. The chemotaxonomic significance of these results is discussed.

Cucurbitane triterpenoids from the leaves of Momordica foetida

The chloroform extract of the leaves of Momordica foetida has yielded 3β, 7β, 23ξ-trihydroxycucurbita-5,24-dien-19-al, 3β, 7β; 25-trihydroxycucurbita-5,23-dien-19-al and 3β,7β-dihydroxy-25-methoxycucurbita-5,23-dien-19-al and the novel compounds 5β,19-epoxy-25-methoxycucurbita-6,23-diene-3β,19-diol, 5β,19-epoxycucurbita-6,23-diene-3β,19,25-triol, 5β,19-epoxy-19-methoxycucurbita-6,23-diene-3β,25-diol, 5β,19-epoxy-19,25-dimethoxycucurbita-6,23-dien-3β-ol and 5β,19-epoxy-25-methoxy-cucurbita-6,23-dien-3β-ol.

Antibacterial activity and isolation of active compounds from fruit of the traditional African medicinal tree Kigelia africana

The fruits of Kigelia africana (Lam.) Benth. are a popular source of traditional medicine throughout Africa. The stembark has been widely analysed for pharmacological activity, yet knowledge of the fruits is limited, despite more extensive use in traditional remedies. Crude extracts of stembark and fruits were prepared with distilled water, ethanol or ethyl acetate. In the microtitre plate bioassay, stembark and fruit extracts showed similar antibacterial activity against Gram-negative and Gram-positive bacteria. A mixture of three fatty acids exhibiting antibacterial effects was isolated from the ethyl acetate extract of the fruits using bioassay-guided fractionation. Palmitic acid, already known to possess antibacterial activity, was the major compound in this mixture. These results confirm antibacterial activity of K. africana fruits and stembark, and support the traditional use of the plant in therapy of bacterial infections.

Homoisoflavanones and stilbenoids from Scilla nervosa

Abstract The bulbs of Scilla nervosa have yielded three novel compounds, 5,7-dimethoxy-3-(4-methoxybenzyl)chroman-4-one, 5-hydroxy-7-methoxy-3-(3-hydroxy-4-methoxybenzyl)-chroman-4-one, 5,7-dimethoxy-3-(4-hydroxybenzyl)chroman-4-one and the known compounds 5-hydroxy-7-methoxy-3-(4-methoxybenzyl)chroman-4-one, ( E )-5,7-dihydroxy-3-(4-hydroxybenzylidene)chroman-4-one, ( E )-resveratrol and ( E )-3,3′,5-trihydroxy-4′-methoxystilbene (rhapontigenin).

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.

Limonoids from Turraea holstii and Turraea floribunda

Abstract Investigations of the stem and root bark of Turraea holstii have yielded the known 1,3-diacetylvilasinin and seven novel limonoids: 11- epi -toonacilin, 11 β ,12 α -diacetoxycedrelone, 12- O -methylnimbolinin B, 12 α -acetoxyneotrichilenone, 12 α -acetoxy-7-acetyl-1,2-dihydroneotrichilenone, 12 α -acetoxy-1,2-dihydroneotrichilenone and 11 β -acetoxy-7-acetyl-12 α -hydroxy-1,2-dihydroneotrichilenone. The stereochemistry at C-11 in turraflorins A–C from Turraea floribunda has been revised.

Pentacyclic triterpenoid and saponins from Gambeya boukokoensis.

Chemical studies of the EtOAc extract of Gambeya boukokoensis Aubr. et Pellegr. stem bark led to the isolation of eight compounds. Three of them were elucidated as new compounds and designated as: gamboukokoensein A, 1alpha,2alpha,3beta,19alpha,23-pentahydroxyurs-12-en-28-oic acid; gamboukokoenside A, 2beta,3beta,6beta,28-tetrahydroxyolean-12-en-23-oic acid 23-O-alpha-L-arabinopyranosyl ester and gamboukokoenside B, 6beta,28-dihydroxy-3-oxoolean-12-en-23-oic acid 23-O-alpha-L-arabinopyranosyl ester. The other five compounds were known and identified as myrianthic acid, protobassic acid, oleanolic acid, erythrodiol and chondrillasterol. Their structures were elucidated on the basis of one and two dimensional NMR spectroscopic techniques, FABMS, ESMS and chemical evidence.

Limonoids from Aphanamixis polystacha

The hexane extract of the seed of Aphanamixis polystacha (Meliaceae) has yielded kihadalactone A and three novel limonoids, rohituka-12, rohituka-13 and rohituka-14. The substitution at C-1 of polystachin has been re-assigned as α.