Effect of Solvent on the Optical Rotation of Azatryptophan Derivatives.

被引量：- 发表：1970

Extracting Scalar Couplings From Complex (1)H NMR Spectra Using a Simple 2D J-Resolved Sequence.

被引量：- 发表：1970

AIM/NBO Analysis of the Geminal Coupling Constants in the Stabilization of A-Type Dimeric Proanthocyanidin: Angular Dependence.

被引量：- 发表：1970

Quantitative analysis of selected alkaloids of Mitragyna speciosa using (1)H quantitative nuclear magnetic resonance spectroscopy.

Mitragyna speciosa is a perennial plant native to Asia, well known for its psychoactive properties. Its major alkaloid mitragynine is known to have sedative and euphoric effects. Hence, the plant has been a subject of abuse, leading to addiction, necessitating efficient analytical methods to detect its psychoactive constituents. However, current chromatography-based methods for detecting the alkaloids are time consuming and costly. Quantitative nuclear magnetic resonance (qNMR) spectroscopy emerges as a promising alternative due to its nondestructive nature, structural insights, and short analysis time. Hence, a rapid and precise qNMR method was developed to quantify selected major psychoactive alkaloids in various parts of M. speciosa. Mitragynine, specioliatine, and speciogynine were quantified in relation to the integral value of the -OCH3 groups of the alkaloids and the internal standard 1,4-dinitrobenzene. The precision and reproducibility of the method gave a relative standard deviation (RSD) of 2%, demonstrating the reliability of the method. In addition, the method showed excellent specificity, sensitivity, high linearity range (R2 = 0.999), and limits of detection (LOD) and quantification (LOQ) values. The analysis revealed that the red-veined M. speciosa leaves contained higher levels of mitragynine (32.34 mg/g), specioliatine (16.84 mg/g) and speciogynine (7.69 mg/g) compared to the green-veined leaves, stem bark, or fruits.

被引量：- 发表：1970

A theoretical study of the electron paramagnetic resonance spectra and local environment in copper(II) complexes with different imidazole and chlorido ligands.

Copper(II) chloride anionic coordination complexes with different imidazole-derived ligands due to the potential cytotoxic activity play the important role in protein. By investigating the experimental electron paramagnetic resonance (EPR) and ultraviolet-visible (UV-vis) spectra of [CuCl(C6H10N2)4]Cl, [CuCl(C6H10N2)4]Cl, [CuCl2(C4H6N2)4], and [Cu2Cl2(C5H8N2)6]Cl2·2H2O, the local structure of the corresponding Cu2+ centers and the role of different ligands are obtained. Based on the well-agreed EPR parameters and the d-d transitions (10Dq), the four Cu2+ centers show tetragonal and orthorhombic distortion, corresponding to the different anisotropies of EPR signals. In addition, the general rules of governing the impact of methanol in imidazolylalkyl derivatives are also discussed, especially the influence on the local environment (symmetry, distortion, covalency, and crystal field) of above four copper(II) chloride anionic coordination complexes. Therefore, the obtained results in this study will be beneficial to provide a theoretical basis for the experimental design of desired copper-containing imidazolyl alkyl derivatives.

被引量：- 发表：1970