1α,25(OH)2-3-Epi-Vitamin D3, a Natural Physiological Metabolite of Vitamin D3: Its Synthesis, Biological Activity and Crystal Structure with Its Receptor

Background: The 1 alpha,25-dihydroxy-3-epi-vitamin-D(3) (1 alpha,25(OH)(2)-3-epi-D(3)), a natural metabolite of the seco-steroid vitamin D(3), exerts its biological activity through binding to its cognate vitamin D nuclear receptor (VDR), a ligand dependent transcription regulator. In vivo action of 1 alpha,25(OH)(2)-3-epi-D(3) is tissue-specific and exhibits lowest calcemic effect compared to that induced by 1 alpha,25(OH)(2)D(3). To further unveil the structural mechanism and structure-activity relationships of 1 alpha,25(OH)(2)-3-epi-D3 and its receptor complex, we characterized some of its in vitro biological properties and solved its crystal structure complexed with human VDR ligand-binding domain (LBD). Methodology/Principal Findings: In the present study, we report the more effective synthesis with fewer steps that provides higher yield of the 3-epimer of the 1 alpha,25(OH)(2)D(3). We solved the crystal structure of its complex with the human VDR-LBD and found that this natural metabolite displays specific adaptation of the ligand-binding pocket, as the 3-epimer maintains the number of hydrogen bonds by an alternative water-mediated interaction to compensate the abolished interaction with Ser278. In addition, the biological activity of the 1 alpha,25(OH)(2)-3-epi-D(3) in primary human keratinocytes and biochemical properties are comparable to 1 alpha,25(OH)(2)D(3). Conclusions/Significance: The physiological role of this pathway as the specific biological action of the 3-epimer remains unclear. However, its high metabolic stability together with its significant biologic activity makes this natural metabolite an interesting ligand for clinical applications. Our new findings contribute to a better understanding at molecular level how natural metabolites of 1 alpha,25(OH)(2)D(3) lead to significant activity in biological systems and we conclude that the C3-epimerization pathway produces an active metabolite with similar biochemical and biological properties to those of the 1 alpha,25(OH)(2)D(3)

Ulepszona procedura izolacji i przygotowania do analizy w ukłądzie GC-MS lotnych produktów reakcji Maillarda

The new method of isolation and preparation for GC-MS analysis of volatile compounds from processed meat and Model Maillard reactions products was investigated. Volatiles after separation with nitrogen stream were trapped in cooled (with solid CO₂ - ethanol bath) steel pipe, filled with glass beeds and subsequently washed out with diethyl ether. The results obtained showed usefulness of this method both for model systems and foodstuffs as well.Przebadano możliwość wydzielenia i przygotowania do analizy w układzie chromatograf gazowy-spektrometr masowy lotnych produktów reakcji Maillarda z układów modelowych typu aminokwas-cukier oraz lotnych związków zapachowych wydzielonych z polędwicy wołowej pieczonej. Stwierdzono, iż metoda polegająca na wydzieleniu tych związków strumieniem gazu obojętnego, osadzeniu ich na nośniku o umiarkowanie rozwiniętej powierzchni (szklane perełki 80/100 mesh) umieszczonym w kolumnie pomocniczej, a następnie wymyciu ich eterem, umożliwia otrzymanie próbki odpowiedniej do przeprowadzenia takiej analizy. Łagodne warunki wydzielania i wymywania powodują, iż tworzenie się artefaktów jest mało prawdopodobne. Chłodzenie kolumny pomocniczej do niskich temperatur umożliwia wyłapanie związków o szerokim spektrum temperatur wrzenia. Metoda może znaleźć ogólne zastosowanie do badania lotnych związków produktów spożywczych