Rapid and efficient purification of naphthodianthrones from St. John's wort extract by using liquid–liquid extraction and SEC
Bibliographic record
Abstract
Hypericin and pseudohypericin, the main naphthodianthrones present in Hypericum species are among the most promising natural products, but the research concerning their biological activities is hindered by their low content in the plant. In this paper a method for the rapid isolation of hypericin and pseudohypericin from Hypericum perforatum hydro-alcoholic dried extracts has been developed. Briefly, the method consists of a partition of the extract between organic and aqueous layers and further purification of the richest extract in naphthodianthrones with Sephadex LH-20 column chromatography. A final separation of hypericin from pseudohypericin was achieved using Sephadex LH-60 column chromatography. All partitions were carried out in triplicate and monitored by LC-MS and NMR analyses. The best results were obtained by successive extraction with n-hexane, Et(2)O and EtOAc. A three-step fractionation resulted in 98% content in total naphthodianthrones. To the best of our knowledge this is the first report on the separation of hypericin from pseudohypericin using size exclusion chromatography.
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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 | 0.000 | 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) | 0.001 | 0.001 |
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".