Occurrence of sesquiterpene derivatives in Scleria striatonux de wild (Cyperaceae).

Scleria striatonux (Cyperaceae), a spice traditionally used in Cameroon, displayed an antiplasmodial activity. Two new sesquiterpenes, 1 (sclerienone A) and 2 (sclerienone B), have subsequently been isolated from the methylene chloride/methanol extract of the rhizome. Their separation involved a combination of methods including repeated silica gel open column chromatography, Sephadex LH-20 and semi-preparative HPLC. Structure elucidation was achieved by means of chemical tests and extensive spectral studies.

Identification of flavonols in leaves of Maytenus ilicifolia and M. aquifolium (Celastraceae) by LC/UV/MS analysis.

A comparative analysis of the flavonoid components of the leaves of two medicinal plants known in Brazil as "espinheira santa", namely, Maytenus ilicifolia Mart. ex Reiss. and M. aquifolium Mart. (Celastraceae), and a hybrid plant, M. aquifoliumxM. ilicifolia, has been carried out using high-performance liquid chromatography coupled with photodiode array UV detection and mass spectrometry. One methoxyflavonoid glycoside and 18 flavonol-3-O-glycosides were identified in the extracts on the basis of their on-line UV spectra (measured in the absence and presence of shift reagents) and multiple stage mass spectral data. Fingerprint analysis of the flavonoid extracts revealed significant differences in the profiles of the two Maytenus species, while the hybrid plant contained flavonoids found in both parent species.

Xanthones from Gentiana campestris as new acetylcholinesterase inhibitors.

In order to discover new acetylcholinesterase (AChE) inhibitors, different plant extracts were screened by a previously established TLC bioautographic method. The methanol extract of Gentiana campestris leaves exhibited significant inhibition of AChE activity. A bioactivity-guided fractionation approach was undertaken to isolate the active components. Four xanthones, bellidin, bellidifolin, bellidin 8-O-beta-glucopyranoside (norswertianolin), and bellidifolin 8-O-beta-glucopyranoside (swertianolin), were found to be responsible for the anti-AChE activity effects. Bellidifolin showed similar activity to galanthamine in this enzyme assay.

Qualitative and quantitative determination of yohimbine in authentic yohimbe bark and in commercial aphrodisiacs by HPLC-UV-API/ MS methods.

The development and validation of a rapid qualitative and quantitative method based on an HPLC-UV-MS technique with atmospheric pressure chemical ionisation and electrospray ionisation for the analysis of yohimbine in a number of commercial aphrodisiac products is reported. HPLC with multiple-stage mass spectrometry experiments allowed the identification of the target compound and increased the selectivity of complex analyses such as those involved with multi-botanical preparations. The precision and the robustness of the method were improved by the use of two internal standards: codeine for UV detection and deuterium-labelled yohimbine for MS detection. Twenty commercial aphrodisiac preparations were analysed and the amount of yohimbine measured and expressed as the maximal dose per day suggested on product labels ranged from 1.32 to 23.16 mg.

Liquid chromatography with ultraviolet absorbance-mass spectrometric detection and with nuclear magnetic resonance spectroscopy: a powerful combination for the on-line structural investigation of plant metabolites.

In order to discover new bioactive compounds from plant sources which could become new leads or new drugs, extracts should be submitted at the same time to chemical screening and to various biological or pharmacological targets. Metabolite profiling using hyphenated techniques such as LC/UV, LC/MS and more recently LC/NMR, quickly provides plenty of structural information, leading to a partial or a complete on-line de novo structure determination of the natural products of interest. As a complement to this approach, bioassays performed after LC/microfractionation of the extracts allow efficient localisation of the bioactive LC-peaks in the chromatograms. The combination of metabolite profiling and LC/bioassays provides the possibility of distinguishing between already known bioactive compounds (dereplication) and new molecules directly in crude plant extracts. Thus, the tedious isolation of compounds of low interest can be avoided and targeted isolation of new bioactive products or constituents presenting novel or unusual spectroscopic features can be undertaken. Several examples of rapid localisation of bioactive compounds, based on post-chromatographic bioautographic testing of LC/NMR microfractions and subsequent on-line identification will be illustrated. Application of hyphenated techniques for the efficient characterisation of labile constituents or constituents difficult to separate at the preparative scale will also be mentioned. The possibilities and limitations of LC/UV/NMR/MS and LC/bioassay as well as future development expected in this field will be discussed.

Antifungal and antioxidant compounds from the root bark of Fagara zanthoxyloides.

Phytochemical investigation of the CH 2 Cl 2 extract of Fagara zanthoxyloides Lam. (Rutaceae) led to the isolation of eleven compounds. One phenylethanoid derivative is a new natural product. The isolation of the antifungal and the antioxidant compounds was monitored by direct TLC bioautographic assays. The structures of the isolated compounds were elucidated by classical spectroscopic methods including UV, NMR, MS and HR-MS.

Absolute configuration of a tetrahydrophenanthrene from Heliotropium ovalifolium by LC-NMR of its Mosher esters.

A new tetrahydrophenanthrene (1, (1R,2R)-1-hydroxy-2-methoxy-6,9-dimethyl-2,3-dihydrophenanthren-4(1H)-one (heliophenanthrone)) has been isolated from the aerial parts of Heliotropium ovalifolium. Its structure was elucidated on the basis of spectroscopic data, and the absolute configuration of the asymmetric centers was determined from LC-NMR data of the Mosher ester derivatives.

Complete LC/MS analysis of a Tinnevelli senna pod extract and subsequent isolation and identification of two new benzophenone glucosides.

The hydroalcoholic extract of Tinnevelli senna is widely used as a laxative phytomedicine. In order to improve the knowledge of the chemical composition of this extract, LC/MS and LC/MS(n) studies were performed, allowing the on-line identification of most of the known constituents, i. e., flavonoids, anthraquinones and the typical dianthronic sennosides. However, the identity of four compounds could not be ascertained on-line under the given LC/MS conditions. These substances were isolated and their structures elucidated as kaempferol, the naphthalene derivative tinnevellin 8-glucoside and two new carboxylated benzophenone glucosides.

Liquid chromatography-atmospheric pressure chemical ionisation/mass spectrometry: a rapid and selective method for the quantitative determination of ginkgolides and bilobalide in ginkgo leaf extracts and phytopharmaceuticals.

In order to evaluate the composition of active constituents in phytopharmaceutical preparations, valid analytical methods are required. For the determination of the active terpene constituents of Ginkgo biloba (the ginkgolides and bilobalide), a liquid chromatography-mass spectrometry (LC-MS) method has been developed using atmospheric pressure chemical ionisation (APCI) in the negative ion mode. This detection mode was found to be much more sensitive and selective compared to UV; indeed the ginkgo terpene trilactones lack strong UV chromophores and flavonoids interfere with their UV detection. LC-APCI/MS detection allowed a considerable reduction in analysis time when compared to LC-UV, because LC resolution was only needed between the pair of isomers ginkgolide B and ginkgolide J. All compounds were selectively detected by single ion monitoring of their specific deprotonated molecules [M-H]-. The samples were directly injected without pre-purification, and a fast gradient was applied, reducing the total time of analysis to 14 min. With this method, the ginkgo terpene trilactones were detected on-line in the picogram range. Several commercial ginkgo preparations on the Swiss market were analysed, and the ginkgolide and bilobalide contents were evaluated using the method described.