Showing papers by "Yong Du published in 2021"

Terahertz and Raman Spectroscopic Investigation of Monohydrate Cocrystal of Antitubercular Isoniazid with Protocatechuic Acid.

Abstract: Pharmaceutical cocrystal provides an alternative modification strategy for the formulation development of drugs owning to their potential ability to improve the physicochemical properties of active pharmaceutical ingredients (APIs) efficiently by changing inter-molecular interactions between raw materials. Isoniazid (INH) is an indispensable main drug for the treatment of tuberculosis, but its tablet formulation is unstable and prone to degradation. In the present study, the monohydrate cocrystal of INH and protocatechuic acid (PA) was prepared by solvent evaporation using PA as cocrystal former to optimize the properties of INH. The parent materials and corresponding 1:1 molar ratio INH-PA monohydrate cocrystal have been characterized by the terahertz time-domain (THz-TDS) and Raman spectroscopy. The THz absorption spectra displayed that there were obvious differences between the peaks of experimental cocrystal and the parent materials, and the same situation was found in Raman vibrational spectra. In addition, density functional theory (DFT) was applied to simulating and optimizing the structure of INH-PA monohydrate cocrystal and supplied corresponding vibrational modes. Our results provided a unique method to characterize the formation of INH-PA monohydrate cocrystal at the molecular-level and a lot of information about cocrystal structure and intra-molecular and/or inter-molecular hydrogen bond interactions in the emerging pharmaceutical cocrystal fields.

Electron transfer from guanosine to the lowest triplet excited state of 4-nitroindole through hydrogen-bonded complex

Abstract: The photochemical reaction of 4-nitroindole and guanosine was studied with the transient absorption spectroscopy as guanine is an effective hole trap during the charge transfer in DNA, and 4-nitroindole is a universal base. Excitation of 4-nitroindole generates the lowest triplet excited state 4-nitroindole (3HN-NO2) within 10 ns in the quantum yield 0.41. 3HN-NO2 has increased basicity compared to its ground state. Consequently, its nitro group exhibits the hydrogen bond accepting ability. 3HN-NO2 can interact with guanosine (G) to form the hydrogen-bonded 3HN-NO2…G complex with the rate constant k=(8.7 ± 0.3)×109 M−1⋅s−1. The hydrogen-bonded complex is identified based on the blue shift evolvement of the absorption maximum of 3HN-NO2 in alcoholic solutions. The reduction potential of 3HN-NO2 is Ered(3HN-NO2) = 1.23 V vs. SCE. The electron transfer occurs in the 3HN-NO2…G complex and generates G+• and HN-NO2−• followed by the proton transfer from N1 and N2 of G producing radicals HN-NO2H•, G(N1-H)• and G(N2-H)•.

Terahertz Investigation of Ternary Drug-bridge-drug Cocrystal Formed between Pyrazinamide, Fumaric Acid and Isoniazid

Abstract: The ternary drug-bridge-drug cocrystal between pyrazinamide (PZA), fumaric acid (FA) and isoniazid (INH) was prepared with the slow solvent evaporation method. The THz absorption spectra presented that there were significantly different peaks between the parent materials and the ternary cocrystal. In addition, density functional theory (DFT) calculations were used to simulate cocrystal structures and provide vibrational modes of the PZA-FA-INH ternary cocrystal.

Investigation into two cocrystals of gliclazide using experimental vibrational spectroscopy combined with DFT theoretical simulation

Abstract: The cocrystals of gliclazide-succinic acid and gliclazide-trometamol under grinding condition have been characterized by terahertz spectroscopical and Raman technique. Spectral results show that both cocrystals have been successfully obtained. The structure of pharmaceutical cocrystal formation has also been characterized with THz spectra.

Cocrystal Formation between Isoniazid and Aromatic Carboxylic Acids Based on Terahertz Spectroscopy

Abstract: Three cocrystals of isoniazid with the aromatic carboxylic acids including p-nitrobenzoic acid, p-cyanobenzoic acid and p-aminobenzoic acid under slow evaporation condition have been synthesized by solvent evaporation. The above three cocrystals were analyzed and characterized by THz spectroscopy.