Analytical investigations of St. John's wort herbal preparations
Notice bibliographique
Résumé
Products containing St. John's wort (Hypericum perforatum L.) have gained popularity as antidepressants. In the UK, they are available as unlicensed medicines and supplements, obtained in a variety of ways from different geographical sources. Some contain dried plant material, whereas others contain standardised extracts, usually to the hypericin and hyperforin content. This thesis describes the application of high performance liquid chromatography-mass spectrometry, to the problem of evaluating the phyto-pharmaceutical quality of St. John's wort preparations available in the UK. Products were compared using fingerprint chromatography and quantitative analysis. A method was established for profiling the major constituents, which were, hyperforin, hypericin, pseudohypericin, rutin, hyperoside, isoquercitrin, quercitrin and chlorogenic acid. Eleven products were analysed and most contained the major constituents. Variation occurred between products standardised to the same hypericin content, although those from established manufacturers were interchangeable. Products from established manufacturers had the highest levels of hyperforin. The cheaper products were not generally of poor quality but less likely to guarantee high levels of the active constituents. The herb was steamed and analysed to investigate the effects on the constituent profile. There was an increase in the level of some flavonoids, chlorogenic acid and hypericin and no change in the hyperforin content. The pseudohypericin content decreased. The degradation of hyperforin and hypericins in the product and extract was evaluated in a three month study. The results showed a low hyperforin and hypericin t90 in both. Hyperforin was more stable in the extract than in pure form. Tandem mass spectrometric investigations showed that hyperforin in extracts and products degraded to give a mixture of oxidation and other breakdovm products, whereas pure hyperforin degraded mainly to its oxidation products. St. John's wort is known to accumulate cadmium. To broaden the criteria for assessing quality, the cadmium content of the products was measured. The amounts of lead, copper, zinc, iron, sodium and potassium were also measured. Cadmium was detected in five, cheaper products, although the amounts found were not considered toxic.
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Comment cette classification a été obtenuedéplier
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,001 | 0,001 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,001 |
| Études des sciences et des technologies | 0,001 | 0,000 |
| Communication savante | 0,000 | 0,002 |
| Science ouverte | 0,001 | 0,000 |
| Intégrité de la recherche | 0,001 | 0,001 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».