Hydrogen bonding effects in the photophysics of a drug, Piroxicam, in homogeneous media and dioxane–water mixtures

Andrade, Suzana M.; Costa, Sı́lvia M. B.

doi:10.1039/a906213k

Cited by 46 publications

(49 citation statements)

References 36 publications

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“…At pH ext 4, water addition to the system favors the neutral form leading to a hypsochromic shift and an increase of φ f (λ exc = 350 nm), which means that ESIPT is also favored. This hypsochromic shift can be quantified using a previous study of Piroxicam in pure solvents (19) that revealed the importance of specific interactions like hydrogen bonds, which determine the absorption spectral features. This solvatochromic behavior was best described by the Kamlet-Taft multiparametric approach.…”

Section: A Absorption Spectra As a Function Of ωmentioning

confidence: 99%

“…This probe has also been shown to be sensitive to the surrounding medium viscosity, as proven by changes in its fluorescence quantum yield, φ f , in pure solvents (19) and aqueous solutions of β-cyclodextrins (14). The empirical relation ln(φ (30) was constructed from data obtained in both protic and nonprotic solvents.…”

Section: B Fluorescence Yieldmentioning

confidence: 99%

“…The photophysics of Piroxicam in a wide range of solvents has shown it to be sensitive to both proticity and polarity, through absorption and emission spectra, and viscosity through its fluorescence yield (19). Furthermore, it was possible to detect (19) and confirm in the water-dioxane mixtures the existence of a critical water concentration (20), which is related to water structural changes from an aggregated to a free solution type (21)(22)(23).…”

Section: Introductionmentioning

confidence: 96%

“…Furthermore, it was possible to detect (19) and confirm in the water-dioxane mixtures the existence of a critical water concentration (20), which is related to water structural changes from an aggregated to a free solution type (21)(22)(23).…”

Section: Introductionmentioning

confidence: 98%

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STRUCTURAL CHANGES IN W/O TRITON X-100/Cyclohexane-Hexanol/Water Microemulsions Probed by a Fluorescent Drug Piroxicam

Andrade¹,

Costa²,

Pansu

2000

Journal of Colloid and Interface Science

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131

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Section: A Absorption Spectra As a Function Of ωmentioning

confidence: 99%

Section: B Fluorescence Yieldmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 98%

See 2 more Smart Citations

STRUCTURAL CHANGES IN W/O TRITON X-100/Cyclohexane-Hexanol/Water Microemulsions Probed by a Fluorescent Drug Piroxicam

Andrade¹,

Costa²,

Pansu

2000

Journal of Colloid and Interface Science

Self Cite

131

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“…9 In protic solvents, a second species called an open conformer (1c, Figure 1) is formed. 10 Furthermore, piroxicam caged within cyclodextrins (CD) and micelles was studied. 9,[11][12][13] At pH = 4, 1 in CD exists as the closed conformer 1b.…”

Section: Introductionmentioning

confidence: 99%

Derivatization of enolic OH of piroxicam: a comparative study on esters and sulfonates

Jayaselli¹,

Cheemala²,

Rani³

et al. 2008

J. Braz. Chem. Soc.

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Vários ésteres e sulfonatos derivados da piroxicam foram preparados por acilação e sulfonação da hidroxila fenólica da piroxicam. Todos os compostos foram avaliados quanto à estabilidade química e às propriedades de inibição da ciclooxigenase. Os dados sugeriram que os ésteres poderiam ser o ponto de partida para o desenvolvimento de fármacos em potencial. Os sulfonatos derivados, preparados pela primeira vez, apresentaram estabilidade. Entre eles, um demonstrou uma moderada seletividade de inibição da COX-2 sobre a COX-1 e teria menor efeito colateral para o sistema gastrintestinal que a piroxicam devido ao grupo OH enólico mascarado. Um mecanismo plausível para o processo de acilação e sulfonação foi proposto, envolvendo a participação da porção da piridina presente na piroxicam. A estrutura molecular de um dos ésteres foi estabelecida, pela primeira vez, por meio de análise cristalográfica dos dados de raio-X de difração de pó.A number of ester and sulfonate derivatives of piroxicam were prepared via acylation/ sulfonation of the enolic OH of piroxicam. All the compounds were evaluated for their chemical stability and cyclooxygenase inhibiting properties. Data suggested that esters could be useful for the development of potential prodrugs. The sulfonate derivatives prepared for the first time were found to be stable. One of them showed a moderately selective COX-2 inhibition over COX-1 and would have lower gastrointestinal side effects than piroxicam due to the masked enolic OH group. A plausible mechanism for the acylation/sulfonation process has been proposed that involves participation of the pyridine moiety of piroxicam. Molecular structure of one of the ester was established for the first time by the crystal structure analysis from X-ray powder data. Keywords: piroxicam, esters, sulfonates, cyclooxygenase IntroductionPiroxicam (1, 1,2-benzothiazine-3-carboxamide-4-hydroxy-2-methyl-N-(2-pyridyl)-1,1-dioxide, Figure 1), 1 a nonsteroidal anti-inflammatory drug (NSAID) that belongs to the enol-carboxamide class, was developed prior to the discovery of cyclooxygenase-2 (COX-2, the second and inducible isoform of cyclooxygenase responsible for inflammation) on the basis of its anti-inflammatory activity and relative safety in animal models. In subsequent studies it was discovered that it possessed moderate COX-2 selectivity in compared to other COX-2 inhibitors. Several attempts were made to improve its pharmacological profile in addition to gastrointestinal side effects. For example, extensive SAR studies have been carried out in order to improve its COX-2/COX-1 selectivity profile which includes substitution at the 6-and 7-positions of the 4-oxo-1,2-benzothiazine-3-carboxamide, alteration of the N-methyl substituent, and amide modification.1 In another approach, the enolic OH group thought to be responsible for its COX-2 selectivity has been exploited as a "handle" for the preparation of various piroxicam derivatives. [2][3][4][5] These derivatives are inactive against cyclooxygenase but converted to piroxic...

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The Quest of Excited‐State Intramolecular Proton Transfer via Eight‐Membered Ring π‐Conjugated Hydrogen Bonding System

Meng

Hsu

Zhang

et al. 2017

Chemistry An Asian Journal

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Searching for eight-membered ring π-conjugated hydrogen bonding (8-MR H-bonding) systems with excited-state intramolecular proton transfer (ESIPT) property is seminal and synthetically challenging. In this work, a series of π-conjugated molecules (8-HB-1, 8-HB-L1 and 8-HB-2) potentially possessing 8-MR H-bonding are strategically designed, synthesized and characterized. The configurations of these three potential molecules are checked by their X-ray structures, among which 8-HB-L1 (a structurally locked 8-HB-1 core chromophore) is proved to be an 8-MR H-bonding system, whereas 8-HB-1 and 8-HB-2 are too sterically hindered to form the 8-MR intramolecular H-bond. The ESIPT property of 8-HB-L1 is confirmed by the dual fluorescence consisting of normal and proton-transfer tautomer emissions. The insight into the ESIPT process of 8-HB-L1 is provided by femtosecond fluorescence upconversion measurements together with computational simulation. The results demonstrate for the first time a successful synthetic route to attain the 8-MR H-bonding molecule 8-HB-L1 with ESIPT property.

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Hydrogen bonding effects in the photophysics of a drug, Piroxicam, in homogeneous media and dioxane–water mixtures

Cited by 46 publications

References 36 publications

STRUCTURAL CHANGES IN W/O TRITON X-100/Cyclohexane-Hexanol/Water Microemulsions Probed by a Fluorescent Drug Piroxicam

STRUCTURAL CHANGES IN W/O TRITON X-100/Cyclohexane-Hexanol/Water Microemulsions Probed by a Fluorescent Drug Piroxicam

Derivatization of enolic OH of piroxicam: a comparative study on esters and sulfonates

The Quest of Excited‐State Intramolecular Proton Transfer via Eight‐Membered Ring π‐Conjugated Hydrogen Bonding System

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