Tautomeric transformations of piroxicam in solution: a combined experimental and theoretical study

Ivanova, Daniela; Deneva, Vera; Nedeltcheva, Daniela; Kamounah, Fadhil S.; Gergov, Georgi; Hansen, Poul Erik; Kawauchi, Susumu; Antonov, Liudmil

doi:10.1039/c5ra03653d

Cited by 42 publications

(26 citation statements)

References 50 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Ethanol had no effect on the UV absorption of Prx at this wavelength [26]. The following equation was obtained and it was used for determining the concentration of Prx in all investigated solutions: y = 0.0485x − 0.0168 R 2 = 0.9996 …”

Section: Resultsmentioning

confidence: 99%

Effect of Cyclodextrin Types and Co-Solvent on Solubility of a Poorly Water Soluble Drug

et al. 2016

View full text Add to dashboard Cite

The aim of the study was to investigate the solubility of piroxicam (Prx) depending on the inclusion complexation with various cyclodextrins (CDs) and on ethanol as a co-solvent. The phase-solubility method was applied to determine drug solubility in binary and ternary systems. The results showed that in systems consisting of the drug dissolved in ethanol–water mixtures, the drug solubility increased exponentially with a rising concentration of ethanol. The phase solubility measurements of the drug in aqueous solutions of CDs, β-CD and γ-CD exhibited diagrams of AL-type, whereas 2,6-dimethyl-β-CD revealed AP-type. The destabilizing effect of ethanol as a co-solvent was observed for all complexes regardless of the CD type, as a consequence of it the lowering of the complex formation constants. In systems with a higher concentration of ethanol, the drug solubility was increased in opposition to the decreasing complex formation constants. According to this study, the type of CDs played a more important role on the solubility of Prx, and the use of ethanol as a co-solvent exhibited no synergistic effect on the improvement of Prx solubility. The Prx solubility was increased again due to the better solubility in ethanol.

show abstract

Section: Resultsmentioning

confidence: 99%

Effect of Cyclodextrin Types and Co-Solvent on Solubility of a Poorly Water Soluble Drug

et al. 2016

View full text Add to dashboard Cite

show abstract

“…It shows very good results in predicting the position of tautomeric equilibria for compounds with intramolecular hydrogen bonds. 14,[24][25][26][27] For comparison some additional functionals as implemented in Gaussian 09 D.01 (B3LYP 28 , MN12SX 29 , BHandH 30 ) were used as well. Second and higher order Møller-Plesset perturbation theory (MP2-4) 31 and coupled-cluster theory with single, double, and perturbative triple excitations (CCSD(T)) 32 were used in addition for calculations of the ground state.…”

Section: Theoretical Calculationsmentioning

confidence: 99%

Dynamics of excited state proton transfer in nitro substituted 10-hydroxybenzo[h]quinolines

Marciniak

Hristova

Deneva

et al. 2017

Phys. Chem. Chem. Phys.

Self Cite

View full text Add to dashboard Cite

The ground state tautomerism and excited state intramolecular proton transfer (ESIPT) of 10-hydroxybenzo[h]quinoline (HBQ) and its nitro derivatives, 7-nitrobenzo[h]quinolin-10-ol (2) and 7,9-dinitrobenzo[h]quinolin-10-ol (3), have been studied in acetonitrile using steady state as well as time dependent spectroscopy and quantum-chemical calculations. In addition to the enol form absorbance in the range 360-390 nm, the absorption spectra of 2 and 3 exhibit a red shifted band at ∼450 nm. Chemometric data processing, based on individual band decomposition, allowed us to estimate the position of the ground state enol-keto tautomeric equilibrium (ΔG values of 1.03 and 0.62 kcal mol respectively for 2 and 3). The fluorescence stems from the keto form even if the enol form is optically excited as proven by the shape of the excitation spectra indicating that ESIPT takes place. The Stokes shift of the substituted compounds is substantially lower compared to HBQ, which follows from the fact that the substitution occurs in the formal cyclohexa-2,4-dienone moiety and leads to a decrease of the HOMO level of the keto tautomer. The pump-probe experiments show that in the nitro substituted HBQs 2 and 3 ESIPT occurs with a time constant of 0.89 ps and 0.68 ps, respectively. In both cases a mixture of the enol and proton transfer forms is optically excited. The enol form exhibits then the ESIPT and subsequently both fractions take the same relaxation path. We propose that in 2 and 3 the ESIPT path exhibits a potential energy barrier resulting in an incoherent rate governed process while in HBQ the ESIPT proceeds as a ballistic wavepacket motion along a path without significant barriers. The theoretical calculations (M06-2X/TZVP) confirm the existence of a barrier in the ground and excited states as result of the substitution.

show abstract

“…Benzosultams, a subclass of bicyclic sulfonamides, are found in numerous biologically active compounds, pharmaceuticals, as well as agricultural agents [ 3 , 4 , 5 , 6 , 7 ]. They exhibit a wide spectrum of promising bioactivities, such as antibacterial, antidiabetic, anticancer, and vitro HPPD (4-hydroxyphenylpyruvate dioxygenase) inhibitory activities, which have been widely utilized as inhibitors and drugs [ 8 , 9 , 10 , 11 , 12 ]. Representative examples have been outlined in Scheme 1 .…”

Section: Introductionmentioning

confidence: 99%

Recent Advances in Catalytic Synthesis of Benzosultams

Zhao

2020

Molecules

View full text Add to dashboard Cite

Benzosultams represent one category of multi-heteroatom heterocyclic scaffolds, which have been frequently found in pharmaceuticals, agricultural agents, and chiral catalysts. Given the diversely significant functions of these compounds in organic and medicinal chemistry, great efforts have been made to develop novel catalytic systems for the efficient construction of benzosultam motifs over the past decades. Herein, in this review, we mainly summarize the recent advances in the field of catalytic synthesis of benzosultams from 2017 to August of 2020, with an emphasis on the scopes and mechanisms of representative reactions.

show abstract

Tautomeric transformations of piroxicam in solution: a combined experimental and theoretical study

Abstract: Piroxicam tautomerism was studied in solution. Enol-amide tautomer is presented mainly as a sandwich type dimer in ethanol and DMSO. The addition of water leads to gradual shift of the equilibrium towards the zwitterionic tautomer.

Cited by 42 publications

References 50 publications

Effect of Cyclodextrin Types and Co-Solvent on Solubility of a Poorly Water Soluble Drug

Effect of Cyclodextrin Types and Co-Solvent on Solubility of a Poorly Water Soluble Drug

Dynamics of excited state proton transfer in nitro substituted 10-hydroxybenzo[h]quinolines

Recent Advances in Catalytic Synthesis of Benzosultams

Contact Info

Product

Resources

About