Solid-state trans–cis isomerization of captopril determined by thermal Fourier transform infrared (FT-IR) microspectroscopy

Wang, Shunli; Lin, Shan‐Yang; Chen, Ting-Fang; Chuang, Chi-Hsiang

doi:10.1002/jps.1056

Cited by 25 publications

(8 citation statements)

References 16 publications

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“…The sample disc was previously equilibrated at the starting temperature (30°C) for about 3 min and then heated to 170°C. The thermal‐responsive IR spectra were recorded with respect to the temperature 13…”

Section: Methodsmentioning

confidence: 99%

Hydration-Induced Proton Transfer in the Solid State of Norfloxacin

Wang

Chen

et al. 2002

Journal of Pharmaceutical Sciences

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Section: Methodsmentioning

confidence: 99%

Hydration-Induced Proton Transfer in the Solid State of Norfloxacin

Wang

Chen

et al. 2002

Journal of Pharmaceutical Sciences

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“…Similar behavior for an API, captopril, containing amide bond but in an initially crystalline form, was observed by Wang et al using VT FT-IR microscopy. 58 Similarly amide cis−trans interconversion in the solid state was postulated as the origin of polymorphism in fosinopril sodium using SSNMR and FT-IR. 59 1 H Solid-State NMR.…”

Section: ■ Introductionmentioning

confidence: 99%

“…58 Similarly amide cis-trans interconversion in the solid state was postulated as the origin of polymorphism in fosinopril sodium using SSNMR and FT-IR. …”

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confidence: 99%

Characterization of Two Distinct Amorphous Forms of Valsartan by Solid-State NMR

et al. 2015

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Valsartan (VAL) is an antihypertensive drug marketed in an amorphous form. Amorphous materials can have different physicochemical properties depending on preparation method, thermal history, etc., but the nature of such materials is difficult to study by diffraction techniques. This study characterizes two different amorphous forms of valsartan (AR and AM) using solid-state NMR (SSNMR) as a primary investigation tool, supported by solution-state NMR, FT-IR, TMDSC, and dissolution tests. The two forms are found to be clearly distinct, with a significantly higher level of structural arrangement in the AR form, as observed in 13C, 15N, and 1H SSNMR. 13C and 15N NMR indicates that the fully amorphous material (AM) contains an approximately equal ratio of cis–trans conformers about the amide bond, whereas the AR form exists mainly as one conformer, with minor conformational “defects”. 1H ultrafast MAS NMR shows significant differences in the hydrogen bonding involving the tetrazole and acid hydrogens between the two materials, while 15N NMR shows that both forms exist as a 1,2,3,4-tetrazole tautomer. NMR relaxation times show subtle differences in local and bulk molecular mobility, which can be connected with the glass transition, the stability of the glassy material, and its response to aging. Counterintuitively the fully amorphous material is found to have a significantly lower dissolution rate than the apparently more ordered AR material.

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“…The domain peak ranging from 1596∼1588 cm −1 was assigned to the C=O stretching of amide in the structure of captopril. Another minor peak at 1722 cm −1 due to the C=O stretching band of carboxylic acid was found for captopril in pH 3.0 buffer solution, which was lower than the pKa 3.7 of captopril (28,29).…”

Section: Resultsmentioning

confidence: 91%

Vibrational Spectroscopic Studies on the Disulfide Formation and Secondary Conformational Changes of Captopril–HSA Mixture after UV‐B Irradiation

Li¹,

Lin²

2005

Photochem & Photobiology

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The effects of pH and ultraviolet-B (UV-B) irradiation on the secondary structure of human serum albumin (HSA) in the absence or presence of captopril were investigated by an attenuated total reflection (ATR)/Fourier transform infrared (FTIR) spectroscopy. The UV-B exposure affecting the stability of captopril before and after captopril-HSA interaction was also examined by using confocal Raman microspectroscopy. The results indicate that the transparent pale-yellow solution for captopril-HSA mixture in all pH buffer solutions, except pH 5.0 approximately 7.0, changed into a viscous form then a gel form with UV-B exposure time. The secondary structural transformation of HSA in the captopril-HSA mixture with or without UV-B irradiation was found to shift the maxima amide I peak in IR spectra from 1652 cm(-1) assigned to alpha-helix structure to 1622 cm(-1) because of a beta-sheet structure, which was more evident in pH 3.0, 8.0 or 9.0 buffer solutions. The Raman shift from 1653 cm(-1) (alpha-helix) to 1670 cm(-1) (beta-sheet) also confirmed this result. Captopril dissolved in distilled water with or without UV-B irradiation was determined to form a captopril disulfide observed from the Raman spectra of 512 cm(-1), which was exacerbated by UV-B irradiation. There was little disulfide formation in the captopril-HSA mixture even with long-term UV-B exposure, but captopril might interact with HSA to change the protein secondary structure of HSA whether there was UV-B irradiation or not. The pH of the buffer solution and captopril-HSA interaction may play more important roles in transforming the secondary structure of HSA from alpha-helix to beta-sheet in the corresponding captopril-HSA mixture than UV-B exposure. The present study also implies that HSA has the capability to protect the instability of captopril in the course of UV-B irradiation. In addition, a partial unfolding of HSA induced by pH or captopril-HSA interaction under UV-B exposure is proposed.

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Solid-state trans–cis isomerization of captopril determined by thermal Fourier transform infrared (FT-IR) microspectroscopy

Cited by 25 publications

References 16 publications

Hydration-Induced Proton Transfer in the Solid State of Norfloxacin

Hydration-Induced Proton Transfer in the Solid State of Norfloxacin

Characterization of Two Distinct Amorphous Forms of Valsartan by Solid-State NMR

Vibrational Spectroscopic Studies on the Disulfide Formation and Secondary Conformational Changes of Captopril–HSA Mixture after UV‐B Irradiation

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