RESUMEN
A square-planar nickel(ii) dithiolate complex is an active molecular catalyst for both photoreduction of protons from water with a turnover number (>1500) and electroreduction of protons from weakly acidic solutions with remarkable turnover frequencies (5575 s-1 at -1.92 V and 1441 s-1 at -1.61 V vs. SCE). DFT calculations provide in-depth insight into the catalytic cycle of the electrochemical reaction, suggesting that the sulfur atoms play crucial roles in proton exchange and hydrogen formation.
RESUMEN
Bufospirostenin A (1) and bufogargarizin C (2), two novel steroids with rearranged A/B rings, were isolated from the toad Bufo bufo gargarizans. Compound 1 represents the first spirostanol found in animals. Compound 2 is an unusual bufadienolide with a cycloheptatriene B ring. Their structures were elucidated by spectroscopic analysis, single crystal X-ray diffraction analysis, and computational calculations.
Asunto(s)
Bufanólidos/química , Bufanólidos/aislamiento & purificación , Bufo bufo , Animales , China , Estructura Molecular , Resonancia Magnética Nuclear BiomolecularRESUMEN
Four new polyphenols, loddigesiinols G-J (compounds 1-4) and a known compound, crepidatuol B (5), were isolated from the stems of Dendrobium loddigesii that have long been used in Traditional Chinese Medicine and have recently been used to treat type 2 diabetes. Compounds 1-5 structures were elucidated based on spectroscopic analysis. The absolute configurations of compounds 1-4 were determined using theoretical calculations of electronic circular dichroism (ECD), and the absolute configuration of compound 5 was determined by a comparison of the experimental ECD spectra and the literature data. Compounds 1-5 are strong inhibitors of α-glucosidase, with IC50 values of 16.7, 10.9, 2.7, 3.2, and 18.9 µM, respectively. Their activities were significantly stronger than trans-resveratrol as a positive control (IC50 values of 27.9 µM).
Asunto(s)
Dendrobium/metabolismo , Inhibidores de Glicósido Hidrolasas/aislamiento & purificación , Fenantrenos/aislamiento & purificación , Polifenoles/aislamiento & purificación , Diabetes Mellitus Tipo 2/tratamiento farmacológico , Inhibidores Enzimáticos/química , Inhibidores Enzimáticos/aislamiento & purificación , Inhibidores de Glicósido Hidrolasas/química , Medicina Tradicional China , Estructura Molecular , Fenantrenos/química , Extractos Vegetales/química , Extractos Vegetales/aislamiento & purificación , Extractos Vegetales/uso terapéutico , Tallos de la Planta/metabolismo , Polifenoles/química , alfa-Glucosidasas/químicaRESUMEN
A simple 4-aniline boron-dipyrromethene (BODIPY) dye (1) was developed as a highly sensitive acidic pH fluorescent probe excitable with visible light based on a photoinduced electron transfer (PeT) mechanism. The pH titration indicates that the fluorescence intensity increases more than 500-fold within the pH range of 4.12-1.42 with a pKa value of 3.24 in methanol-water (1 : 1, v/v) solution, which is valuable for studying strongly acidic conditions. Density functional theory (DFT) calculations reproduce the fluorescence off-on behavior. 1 has also been used as a fluorescent chemosensor for the visual detection of dissolved carbon dioxide (CO2) gas. The underlying mechanism of the sensing process is rationalized. This probe can be recovered by bubbling nitrogen (N2) gas into CO2-treated solutions for over 10 cycles. In addition, two logic gates (OR and INH) have been achieved at the molecular level by changing the initial states of system 1 and chemical inputs.
Asunto(s)
Compuestos de Anilina/química , Compuestos de Boro/química , Dióxido de Carbono/análisis , Colorantes Fluorescentes/síntesis química , Cristalografía por Rayos X , Colorantes Fluorescentes/química , Concentración de Iones de Hidrógeno , Modelos Moleculares , Estructura Molecular , Propiedades de SuperficieRESUMEN
Aristoyunnolins G (1) and H (2), two new diastereoisomeric sesquiterpenes featuring a rare aristophyllene skeleton, were isolated from the traditional Chinese medicine Aristolochia yunnanensis. Their absolute stereochemistry involving three chiral centers was determined by combined chemical, spectral, and Density Functional Theory (DFT) calculation methods.