Isolation of Pyrrolizidine Alkaloid Isomers from Symphytum Species by Semi-Preparative Chiral Chromatography
Bibliographic record
Abstract
Comfrey is a common name given to plants belonging to the genus Symphytum (family Boraginaceae) [1]. The comfrey root and leaf contain varying levels of the hepatotoxic pyrrolizidine alkaloids (PAs) that have been reported to cause veno-occlusive disease in humans [2]. However, the exact alkaloid profile of different species has not been clearly established, in part because comfrey PAs are not commercially available and the isolation of the individual isomers is difficult. Milligram quantities of PA components from Symphytum are needed for use as analytical standards in quantitating these components in dietary supplements containing these botanicals. Results will be presented on the isolation of PAs from the roots of S. uplandicum . Briefly, a 1.0 kg quantity of plant material was extracted with methanol and the PAs were reduced with zinc dust to convert the N-oxides to free bases. The PAs were enriched on a Chem Elut cartridge (Varian Inc.) and then fractionated on a silica gel chromatographic column, followed by further isolation by semi-preparative HPLC. For the compounds occurring as racemic mixtures, their separation was achieved by semi-preparative chiral HPL C. These chiral stationary phases consist of cellulose immobilized on silica with carbamates as chiral selectors (Chiralpak IA and IC, Chiral technologies Inc. West Chester PA). The compositions of individual fractions were monitored by GC-MS or LC-MS and the purified components were characterized by mass and NMR spectroscopic studies [3–5]. The isolated PAs will be used for the development of analytical methods that can be applied to develop chemical profiles of different species of Symphytum and to determine alkaloid contents of comfrey preparations sold in the market. References : [1] Botanical Safety Handbook 1997 CRC Press, Fl. [2] Mei N, et al. (2005) British Journal of Cancer 92: 873–875. [3] Logie CG, et al. (1994) Phytochemistry, 37: 43–109. [4] Roeder E, et al. (1990), Phytochemistry, 29: 11–29. [5] Kim NC, et al. (2001) Journal of Natural Products, 64: 251–253.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.005 | 0.002 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".