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A large body of research shows an association between higher body weight and low vitamin D status, as assessed using serum 25-hydroxyvitamin D concentrations. Vitamin D can be metabolised in adipose tissue and has been reported to influence gene expression and modulate inflammation and adipose tissue metabolism in vitro. However, the exact metabolism of vitamin D in adipose tissue is currently unknown. White adipose tissue expresses the vitamin D receptor and hydroxylase enzymes, substantially involved in vitamin D metabolism and efficacy. The distribution and concentrations of the generated vitamin D compounds in adipose tissue, however, are largely unknown. Closing this knowledge gap could help to understand whether the different vitamin D compounds have specific health effects in the setting of adiposity. This review summarises the current evidence for a role of vitamin D in adipose tissue and discusses options to accurately measure vitamin D compounds in adipose tissue using liquid chromatography tandem mass spectrometry (LC/MS-MS). [ABSTRACT FROM AUTHOR]

Liquid chromatography/tandem mass spectrometry (LC–MS/MS) is widely used to determine vitamin D3 metabolites in biological samples. The ionization efficiencies of these metabolites, however, are poor under electrospray ionization conditions. Moreover, the chromatographic separation of multiple vitamin D metabolites and their epimers can be challenging. For these reasons, chemical derivatization reagents are often used to improve sensitivity and selectivity of analysis. While the derivatization schemes have been proven to be very effective, one missing aspect is the investigation of the stability of the chemical derivatization products in stored sample extracts. In this study, we investigated the long-term stability of several vitamin D3 metabolites after 1 and 3 months of storage at − 20 °C. Five vitamin D3 metabolites were examined after derivatization with seven different derivatization reagents. Generally, Amplifex products were the most stable in the long term in our study with 11–20% degraded after 1 month of storage and 14–35% after 3 months. The stabilities for some of the metabolites′ 4-[2-(6,7-dimethoxy-4-methyl-3-oxo-3,4-dihydroquinoxalyl)ethyl]-1,2,4-triazoline-3,5-dione (DMEQ-TAD), 2-fluoro-1-methylpyridinium p-toluenesulfonate (FMP-TS), isonicotinoyl chloride (INC) and 4-phenyl-1,2,4-triazoline-3,5-dione acetylated (PTAD-Ac) products were also acceptable after 1 month of storage. Other derivatized metabolites, however, degraded extensively already after 1 month of storage, such as 4-phenyl-1,2,4-triazoline-3,5-dione (PTAD) (54–72% degradation) and 2-nitrosopyridine (PyrNO) (32–100% degradation). Importantly, for every metabolite, there was an optimum derivatization reagent that met the criteria of stability proposed by international regulatory bodies after 1 month of storage. Some derivatives were stable for even up to 3 months of storage, with degradation of less than 15%. [ABSTRACT FROM AUTHOR]

We report here that easy ambient sonic spray ionization--mass spectrometry (EASI-MS) allowed direct, rapid, and comprehensive analysis of active components (e.g., terpenetrilactones and intact flavonol glycosides) in Ginkgo tablets. Unlike conventional methods that hydrolyze flavonol glycosides to flavonoids prior to analysis, EASI-MS detects intact flavonol glycosides directly from the tablets enabling differentiation of these natural glycosides from the synthetic flavonoids. Adulteration of Ginkgo tablets is therefore readily recognized in less than 10 s measurement time. Sample preparation is simple and requires only 0.5 mL of methanol and a mortar and pestle. Additionally, no reference standards are needed and a comparison is made to a certified Ginkgo tablet. To demonstrate these abilities, 22 commercial Ginkgo tablets were analyzed by EASI-MS. The data revealed large variations of ingredients and strong deviations from the specified Ginkgo extract levels. These results emphasize the importance of monitoring Ginkgo products using appropriate methodologies as suggested in our work. The technique may replace more demanding LC-MS/MS methods, which can achieve comparable results but are considerably more labor- intensive. Importantly, the presented method is cheaper, faster, and much simpler to operate than chromatography-based mass spectrometric techniques. Key words: easy ambient sonic spray ionization--mass spectrometry (EASI-MS);flavonol glycosides, Ginkgo biloba, terpenetrilactones, Ginkgo tablet adulteration. L'ionisation dans un jet supersonique couplee a la spectrometrie de masse par la technique << easy ambient sonic spray ionization--mass spectrometry >> (EASI-MS) a permis une analyse directe, rapide et complete des ingredients actifs (p.ex. trilactones terpeniques et glycosides de flavonol) dans les comprimes de Ginkgo. Contrairement aux methodes classiques qui comprennent l'hydrolyse des glycosides de flavonol en flavonoides avant l'analyse, la methode EASI-MS permet de detecter les glycosides de flavonol intacts directement dans les comprimes et, donc, de differencier ces glycosides naturels des flavonoides synthetiques. L'adulteration des comprimes de Ginkgo peut ainsi etre detectee facilement au moyen d'une mesure prenant moins de 10 s. Simple, la preparation des echantillons ne requiert que 0,5 mL de methanol ainsi qu'un mortier et un pilon. En outre, aucuns etalons de reference ne sont necessaires, la comparaison etant faite avec un comprime de Ginkgo dont la teneur est certifiee. Pour illustrer les capacites de la methode EASI-MS, on a analyse 22 comprimes de Ginkgo du commerce. Les donnees ont revele de fortes variations de concentration des ingredients et des ecarts importants par rapport aux concentrations d'extrait de Ginkgo specifiees. Ces resultats soulignent l'importance de la surveillance des produits a base de Ginkgo en faisant appel a des methodes appropriees, comme celle proposee dans notre etude. Cette technique pourrait remplacer les methodes CL-SM/SM plus exigeantes, qui produisent des resultats comparables mais demandent beaucoup plus de travail. Fait important, la methode presentee est moins couteuse, plus rapide et beaucoup plus facile a executer que les techniques de spectrometrie de masse conjuguee a la chromatographie. [Traduit par la Redaction] Mots-cles: easy ambient sonic spray ionization--mass spectrometry (EASI-MS), glycosides de flavonol, Ginkgo biloba, trilactones terpeniques, adulteration des comprimes de Ginkgo., Introduction During the last decade, the use of complementary and alternative medicine products has become increasingly popular in western countries. In particular, the use of botanical dietary supplements and herbal [...]

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