Abdulrahman, S.;
(1991)
Analysis of alkaloids from plant cell tissue cultures and other sources.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
Specific and sensitive new analytical procedures for the separation and identification of Cinchona and opium alkaloids have been developed using online high performance liquid chromatography/mass spectrometry (HPLC/MS) with a thermospray (TSP) interface connected to a quadrupole instrument. The Cinchona alkaloid separation was based on the extraction of the alkaloids from Cinchona ledgeriana cells using acid base extraction followed by isocratic reversed-phase HPLC. The eluent consisted of ammonium acetate buffer, methanol, and acetic acid, and a Cie stationary phase was used. The assays will allow the selection of high yielding plant strains and optimisation of the culture process for the production of these and other valuable compounds. The method developed for opium alkaloids allowed simultaneous separation of codeine, thebaine, papaverine, noscapine, morphine and its mono and diacetyl conjugates, using an ammonium acetate buffer and acetonitri1e, an application that has not previously been reported. Morphine was selectively acetylated to 3-monoacetyImorphine and the other metabolites were obtained commercially. This assay will be of value to both clinicians and basic scientists, The TSP spectra of these alkaloids showed only the protonated molecular ions and single ion monitoring provided sensitive and selective detection of the separated compounds. Tandem mass spectrometry experiments were carried out on the protonated molecular ions to allow multiple ion monitoring. Alternative ionisation methods including fast atom bombardment were also investigated, The mass spectra and tandem mass spectra showed significant differences in the stability of the stereoisomers. These differences were used to identify the structural features responsible for their fragmentation in the ion source and they were also related to the biological activity, the epimers being modelled by molecular graphics. It was confirmed that H-bonding is possible in the stable isomers, and the differences in their activities agree with small differences in the Cheng's distances calculated.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Analysis of alkaloids from plant cell tissue cultures and other sources |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Thesis digitised by ProQuest. |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10122692 |
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