Biomedical subjects

K Hostettmann

Publications and source records attributed to K Hostettmann.

114 records · Page 7Linked to original sources

PubMedDate not supplied

On-line identification of the bioactive compounds from Blumea gariepina by HPLC-UV-MS and HPLC-UV-NMR, combined with HPLC-micro-fractionation.

The dichloromethane extract of the aerial parts of Blumea gariepina (Asteraceae) was shown to be active against the phytopathogenic fungus Cladosporium cucumerinum and to inhibit acetylcholinesterase. In order rapidly to identify the active principles, the crude extract was analysed by on-flow HPLC-1H-NMR. HPLC-micro-fractionation was performed and all peaks collected were submitted to assays against C. cucumerinum and acetylcholinesterase. By this means, the biological activities could be efficiently associated with selected HPLC peaks. Complementary on-line structural data for all peaks of interest in the crude extract were obtained from HPLC-MS and from HPLC-UV with post-column addition of UV shift reagents. This chemical screening strategy with integrated bioassays permitted the on-line identification of a number of constituents and gave useful information for an efficient isolation procedure.

Antifungal Agents↗

PubMedDate not supplied

On-line identification of unstable iridoids from Jamesbrittenia fodina by HPLC-MS and HPLC-NMR.

HPLC-UV-MS analysis of the methanol extract of Jamesbrittenia fodina (Wild) O. M. Hilliard (Scrophulariaceae) revealed the presence of different iridoid cinnamic esters; however, isolation of these constituents was prevented by instability problems. HPLC-UV-MS and HPLC-NMR analysis of the mixtures obtained after a tentative isolation indicated that, in the first instance, instability was due to a light-induced cis/trans isomerisation of the cinnamic moieties. Further investigation of related compounds showed an additional instability problem linked to other chemical transformations. A detailed HPLC-NMR-MS study of these fractions demonstrated that the modifications occurred on the rhamnose moiety of these iridoids. It could be concluded that the second type of instability was attributable to transesterification of the cinnamic moiety on the rhamnose unit. The recording of stop-flow HPLC-NMR spectra for specific HPLC peaks permitted the direct monitoring of these transformations. Based on these on-line data, six new unstable aucubin derivatives were efficiently characterised.

Chromatography, High Pressure Liquid↗

PubMedDate not supplied

The determination of huperzine A in European Lycopodiaceae species by HPLC-UV-MS.

A rapid qualitative HPLC-UV-MS method was developed for the detection of huperzine A in Lycopodiaceae species. HPLC coupled with mass spectrometry experiments allowed the identification of the alkaloid and enabled targeted analysis of complex matrices such as herbal extracts. Huperzine A was detected by single ion monitoring of the pseudomolecular ion [M + H]+ at m/z 243.2. The alkaloid was also detected on TLC in a bioautographic enzyme assay with acetylcholinesterase to show the activity of the compound. Four Lycopodiaceae species collected in Switzerland were tested by these methods and Huperzia selago (L.) Bernh. ex Schrank et Martius was the only species found to contain huperzine A.

Alkaloids↗

PubMedDate not supplied

Screening for cytotoxic activity of plants used in traditional medicine.

A total of 260 extracts have been prepared from 75 medicinal plant species collected in Africa, Panama and Mauritius. Three different concentrations of each extract have been screened in vitro for cytotoxic activity using a colorimetric assay to determine cell survival of human colon carcinoma Co115 cells. Fifteen plants showed ED50 values between 10.0 and 1.0 micrograms/ml but more significant activities were obtained in 11 (ED50 range 1.0-0.1 micrograms/ml) and 3 (ED50 range 0.1-0.01 micrograms/ml) plant specimens. Identification of new active substances may well be aided by pre-selecting plants known to be used empirically by traditional healers.

Africa↗

PubMedDate not supplied

Characterization of the polyphenolic composition of purple loosestrife (Lythrum salicaria).

Phenolic compounds of purple loosestrife (Lythrum salicaria L.) were analysed by the use of liquid chromatography-mass spectrometry (LC/MS) equipped with atmospheric pressure chemical ionisation (APCI) and electrospray ionisation (ESI). The presence of vitexin and orientin as well as their isomers, isovitexin and isoorientin, were confirmed using ion trap multiple stage LC/MS3 analysis. Several phenolic acids and tannins were also detected. Ellagitannins, vescalagin and pedunculagin, are reported from the plant for the first time.

Chromatography, High Pressure Liquid↗

PubMedDate not supplied

Phytochemical profiles of Targionia lorbeeriana: grown in vitro and in the open.

The terpenoid constituents of Targionia lorbeeriana grown in vivo and in vitro were compared. The analysis of the dichloromethane extract was performed by HPLC-UV and by HPLC-MS. The obtained results revealed that the sesquiterpene lactones isolated from the dichloromethane extract of the wild Targionia lorbeeriana were also produced by the liverwort in in vitro cultures, in the same relative amounts. The composition of essential oils was evaluated by GC and GC-MS. Both, the yield and diversity of the essential oil obtained from wild growing T. lorbeeriana gametophytes were higher than those growing in vitro. Although, a significant number of compounds produced in vivo were maintained in vitro, a considerable number of other ones were not detected. Instead, under in vitro conditions, some new compounds were found which do not accumulate under wild conditions.

Cells, Cultured↗