Biomedical subjects

Kurt Hostettmann

Publications and source records attributed to Kurt Hostettmann.

At least 37 records · Page 2Linked to original sources

PubMed2004

Identification of the polar constituents of Potamogeton species by HPLC-UV with post-column derivatization, HPLC-MSn and HPLC-NMR, and isolation of a new ent-labdane diglycoside.

The polar extracts of Potamogeton pectinatus, P. lucens, P. perfoliatus and P. crispus (Potamogetonaceae) were analyzed by HPLC-UV-MS and their chromatographic profiles were very similar. The polar constituents of P. pectinatus were more exhaustively investigated by HPLC-UV with post-column derivatization, HPLC-MS(n) and HPLC-NMR, which allowed the on-line identification of various known flavones (dereplication). One of these compounds, luteolin 3'-O-glucoside, has never been characterized in the Potamogeton genus. The HPLC-UV-MS and HPLC-NMR analyses revealed also the presence of ent-labdane diterpene glycosides in the polar extracts of P. pectinatus and P. lucens and led to the isolation of a new ent-labdane diglycoside from P. pectinatus, beta-D-glucopyranosyl-(1-->2)-beta-D-glucopyranosyl-15,16-epoxy-12-oxo-8(17),13(16),14-ent-labdatrien-19-oate.

Chromatography, High Pressure Liquid↗

PubMed2004

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.

Acetylcholinesterase↗

PubMed2003

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.

Chromatography, Liquid↗

PubMed2003

Taxiphyllin from Henriettella fascicularis.

(2R)-alpha-(beta-D-Glucopyranosyloxy)-4-hydroxybenzeneacetonitrile (taxiphyllin) dihydrate, C(14)H(17)NO(7) x 2H(2)O, is a naturally occurring cyanogenetic glycoside which has been isolated from Henriettella fascicularis (Sw.) C. Wright (Melastomataceae). Its structure is stabilized by a wealth of intermolecular O-H...O and O-H...N hydrogen bonds spun into a three-dimensional network. Further stabilization arises from an intramolecular O-H...O bond and weak intermolecular C-H...O interactions. The very anisotropic growth speeds of the basal pinacoids from methanol mirror a certain structural inhomogeneity.

Crystallography, X-Ray↗

PubMed2003

ent-Labdane diterpenes from the aquatic plant Potamogeton pectinatus.

Four new ent-labdane diterpenes were isolated from the freshwater aquatic plant Potamogeton pectinatus, together with two known furano-ent-labdanes. The new compounds were assigned the structures methyl-15,16-epoxy-12(R)-acetoxy- 8(17), 13(16),14-ent-labdatrien-19-oate,15,16-epoxy-12(R)-acetoxy-8(17), 13(16),14-ent-labdatrien-19-oic acid, 8(17),13-ent-labdadien-15 --> 16-lactone-19-oic acid and 16-hydroxy-8(17),13-ent-labdadien-15,16-olid-19-oic acid by spectroscopic means. Some of these labdanes showed a strong algicidal activity against Raphidocelis subcapitata.

Chlorophyta↗

PubMed2003

Antifungal diterpenes from Hypoestes serpens (Acanthaceae).

Two new diterpenes, fusicoserpenol A and dolabeserpenoic acid A, with antifungal activity, were isolated from leaves of Hypoestes serpens (Acanthaceae). Their structures were elucidated by means of spectrometric methods including 1D and 2D NMR experiments and MS analysis. X-ray crystallographic analysis confirmed the structure of fusicoserpenol A and established the relative configuration.

Acanthaceae↗

PubMed2003

New dihydroalkylhexenones from Lannea edulis.

Activity-guided isolation of radical-scavenging compounds from the dichloromethane extract of the root bark of Lannea edulis led to isolation of two known bioactive alkylphenols [cardonol 7 (1) and cardonol 13 (2)], and three new dihydroalkylhexenones were also isolated (3-5). Their structures were elucidated by spectroscopic and chemical methods. The absolute configuration of 4 was determined by the Mosher ester method.

Anacardiaceae↗

PubMed2003

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.

Esters↗

PubMed2003

Tropane alkaloids from the bark of Erythroxylum vacciniifolium.

Eight new tropane alkaloids (1-8) were isolated from the bark of "catuaba", a Brazilian endemic plant Erythroxylum vacciniifolium Martius. Their structures were determined by high-resolution mass spectrometry and multidimensional NMR spectroscopy.

Alkaloids↗

PubMed2003

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.

Anti-Bacterial Agents↗

PubMed2002

Prenylated isoflavonoids from the root bark of Erythrina vogelii.

Four new prenylated isoflavonoids, vogelins D-G (1-4), were isolated from the CH2Cl2 extract of Erythrina vogelii root bark in addition to the known compounds isolupalbigenin (5), ficuisoflavone (6), ulexone (7), isochandalon (8), and isoderrone (9). The structures 1-4 were elucidated by spectroscopic and chemical methods. The absolute configuration of compound 1 was determined on the basis of its CD spectrum. Possible biogenetic relationships among the E. vogelii isoflavonoids are briefly discussed.

Africa, Western↗

PubMed2002

Four new sesquiterpenoid derivatives from the heartwood of Mansonia gagei.

Four new sesquiterpenoid derivatives named mansonones N (1), O (2), P (3), and Q (4) were isolated from a dichloromethane extract of the heartwood of Mansonia gagei, a plant used in folk medicine in Thailand. Their structures were resolved on the basis of spectrometric data interpretation and the single-crystal X-ray analysis of 1 and 2.

Chromatography, Liquid↗

PubMed2002

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.

Benzophenones↗

PubMed2002

An LC/DAD-UV/MS method for the rapid detection of aristolochic acid in plant preparations.

A new method using direct on-line coupling between HPLC and UV-DAD/MS was developed for the rapid detection of aristolochic acid I in plant preparations. The use of both UV-DAD and MS detectors enables this method to be very selective. A ng range detection limit was determined for both UV and MS detections. A quantitative determination of aristolochic acid I in plant preparations was achieved using UV and MS detection. A thin layer chromatography assay was also developed for the preliminary detection of aristolochic acid I in complex mixtures.

Aristolochia↗

PubMed1998

5'-O-demethyldioncophylline A, a new antimalarial alkaloid from triphyophyllum peltatum.

From the root bark of Triphyophyllum peltatum, the new naphthylisoquinoline alkaloid 5'-O-demethyldioncophylline A has been isolated. Its otherwise difficult separation from the largely dominating main alkaloid, dioncophylline A, was greatly facilitated by a bromination-benzylation procedure. From the resulting derivative, a crystal structure analysis with an anomalous X-ray diffraction was achieved, allowing confirmation of the full absolute stereostructure of the new alkaloid. The structure was further corroborated by a partial synthesis from dioncopeltine A. The natural product was shown to exhibit antimalarial activity against erythrocytic forms of Plasmodium falciparum.

Journal Article↗

PubMedDate not supplied

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.

Atmospheric Pressure↗

PubMedDate not supplied

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.

Aphrodisiacs↗

PubMedDate not supplied

Isolation and on-line identification of antioxidant compounds from three Baccharis species by HPLC-UV-MS/MS with post-column derivatisation.

The aqueous extracts of aerial parts of Baccharis trimera (Less.) DC., B. crispa Spreng. and B. usterii Heering (Asteraceae) displayed significant radical scavenging activity in a diphenylpicrylhydrazole (DPPH)/TLC assay. In order to rapidly identify the active principles, the crude extracts were analysed by HPLC-UV, and an HPLC-micro-fractionation of the extract of B. usterii was performed. Six quinic acids derivatives (1-6) were isolated from B. usterii by MPLC. The fractions were monitored by DPPH/TLC assay and a series of radical-scavenging quinic acid derivatives could be identified. The comparison of the HPLC profiles of the extracts of B. usterii, B. trimera and B. crispa was performed. In order to obtain complementary on-line structural information for all peaks of interest, HPLC-MS/MS together with HPLC-UV involving post-column addition of UV shift reagents was undertaken on the crude extract. The interpretation of these data permitted the on-line identification of known compounds, some of which are reported for the first time in this plant.

Antioxidants↗