RESUMEN
ETHNOPHARMACOLOGICAL RELEVANCE: Panax quinquefolius L (PQ), also known as American ginseng, has been used as a medicinal herb for thousands of years in the Far East, which was wildly used actively in healing the cardiovascular, endocrine and immune systems, in supporting chemoprevention of cancer. MATERIALS AND METHODS: An integrated, rapid, sensitive and reliable UHPLC-ESI-QQQ MS/MS method was validated and successfully applied in a pharmacokinetics study in which four representative ginsenosides were measured in beagle plasma following oral administration of Panax quinquefolius L (PQ) in the form of ultrafine granular powder, standard powder and an extract. RESULTS: Two paired ions ([M+Na](+) in the positive MS process, and two characteristic ions [Q3](+) in the positive MS/MS process) of the target compounds were optimized and selected for improved qualitative and quantitative analysis of ginsenosides in beagle plasma. The relative bioavailability of the target ginsenosides in these three formulations was measured by the pharmacokinetic parameters, including Cmax, Tmax, AUC0-∞ and so on. The ultrafine granular powder had the highest bioavailability, as well as the greatest extent of and fastest dissolution in vitro. CONCLUSION: Our results show that improved formulations of PQ could facilitate the dissolution and promote absorption of the important compounds it contains.
Asunto(s)
Ginsenósidos/farmacocinética , Panax/química , Extractos Vegetales/farmacocinética , Animales , Área Bajo la Curva , Disponibilidad Biológica , Perros , Liberación de Fármacos , Ginsenósidos/sangre , Ginsenósidos/química , Semivida , Estructura Molecular , Extractos Vegetales/sangre , Extractos Vegetales/química , PolvosRESUMEN
For imitating the active site of antioxidant selenoenzyme glutathione peroxidase (GPx), an artificial enzyme selenosubtilisin was employed as a scaffold for reconstructing substrate glutathione (GSH) specific binding sites by a bioimprinting strategy. GSH was first covalently linked to selenosubtilisin to form a covalent complex GSH-selenosubtilisin through a Se-S bond, then the GSH molecule was used as a template to cast a complementary binding site for substrate GSH recognition. The bioimprinting procedure consists of unfolding the conformation of selenosubtilisin and fixing the new conformation of the complex GSH-selenosubtilisin. Thus a new specificity for naturally occurring GPx substrate GSH was obtained. This bioimprinting procedure facilitates the catalytic selenium moiety of the imprinted selenosubtilisin to match the reactive thiol group of GSH in the GSH binding site, which contributes to acceleration of the intramolecular catalysis. These imprinted selenium-containing proteins exhibited remarkable rate enhancement for the reduction of H2O2 by GSH. The average GPx activity was found to be 462 U/micromol, and it was approximately 100 times that for unimprinted selenosubtilisin. Compared with ebselen, a well-known GPx mimic, an activity enhancement of 500-fold was observed. Detailed steady-state kinetic studies demonstrated that the novel selenoenzyme followed a ping-pong mechanism similar to the naturally occurring GPx.
Asunto(s)
Glutatión Peroxidasa/metabolismo , Imitación Molecular , Selenio/metabolismo , Sitios de Unión , Catálisis , Electroforesis en Gel de Poliacrilamida , Especificidad por SustratoRESUMEN
A 6A,6A'-dicyclohexylamine-6B,6B'-diselenide-bis-beta-cyclodextrin (6-CySeCD) was designed and synthesized to imitate the antioxidant enzyme glutathione peroxidase (GPX). In this novel GPX model, beta-cyclodextrin provided a hydrophobic environment for substrate binding within its cavity, and a cyclohexylamine group was incorporated into cyclodextrin in proximity to the catalytic selenium in order to increase the stability of the nucleophilic intermediate selenolate. 6-CySeCD exhibits better GPX activity than 6,6'-diselenide-bis-cyclodextrin (6-SeCD) and 2-phenyl-1,2-benzoisoselenazol-3(2H)-one (Ebselen) in the reduction of H(2)O(2), tert-butyl hydroperoxide and cumenyl hydroperoxide by glutathione, respectively. A ping-pong mechanism was observed in steady-state kinetic studies on 6-CySeCD-catalyzed reactions. The enzymatic properties showed that there are two major factors for improving the catalytic efficiency of GPX mimics. First, the substrate-binding site should match the size and shape of the substrate and second, incorporation of an imido-group increases the stability of selenolate in the catalytic cycle. More efficient antioxidant ability compared with 6-SeCD and Ebselen was also seen in the ferrous sulfate/ascorbate-induced mitochondria damage system, and this implies its prospective therapeutic application.