The thermodynamic dissociation constants of methotrexate by the nonlinear regression and factor analysis of multiwavelength spectrophotometric pH-titration data

Abstract

The mixed dissociation constants of methotrexate — chemically (2S)-2-[(4-{[(2,4-diamino-7,8-dihydropteridin-6-yl)methyl] (methyl)amino}phenyl)formamido]pentanedioic acid (the cas number 59-05-2) at various ionic strengths I of range 0.01–0.4, and at temperatures of 25°C and 37°C, were determined with the use of two different multiwavelength and multivariate treatments of spectral data, SPECFIT32 and SQUAD(84) nonlinear regression analyses and INDICES factor analysis according to a general rule of first, determining the number of components, and then calculating the spectral responses and concentrations of the components. Concurrently, the experimental determination of the thermodynamic dissociation constants was in agreement with its computational prediction of the PALLAS programme based on knowledge of the chemical structures of the drug. The factor analysis in the INDICES programme predicts the correct number of light-absorbing components when the data quality is high and the instrumental error is known. Three thermodynamic dissociation constants were estimated by nonlinear regression of {pK a , I} data: for methotrexate pK a1T= 2.895(13), pK a2T= 4.410(14), pK a3T= 5.726(15) at 25°C and pK a1T= 3.089(15), pK a2T= 4.392(12), pK a3T= 5.585(11) at 37°C, where the figure in brackets is the standard deviation in last significant digits. The reliability of the dissociation constants of the drug were proven by conducting goodness-of-fit tests of the multiwavelength spectrophotometric pH-titration data.

Toxicity, Biocompatibility, pH-Responsiveness and Methotrexate Release from PVA/Hyaluronic Acid Cryogels for Psoriasis Therapy

“…It is not recommended to store solution more than one day [ 53 ]. Several p K a values are given in literature for MTX as 4.70 5.6, 4.8, and 3.8 (carboxylic acid) [ 54 , 55 ]. All these characteristics of the HA and MTX will give a pH responsiveness of the MTX-loaded PVA/HA cryogels.…”

Interaction of methotrexate, an anticancer agent, with copper(II) ions: coordination pattern, DNA-cleaving properties and cytotoxic studies

“…The acid–base properties of the moieties, which can be deprotonated with a rise of pH value, were determined using potentiometric measurements (Table 1 ). The first two obtained p K a values: 2.89 and 4.56 correspond to the deprotonation of carboxylic groups from glutamic acid, α-COOH and γ-COOH, respectively (Poe, 1973 , 1977 ; Meloun et al, 2010 ). The highest value of p K a = 5.65 corresponds to the deprotonation process of the heterocyclic nitrogen (N1)H + from the pteridine ring.…”

Glutathione and pH‐responsive fluorescent nanogels for cell imaging and targeted methotrexate delivery

“…As shown in this figure, up to 78% of MTX was released from the NGs in pH 7.4, 40°C, and 10mM GSH after 48 h. In contrast, by reducing the pH value of the medium to 5.3, nearly 85% of loaded MTX was released in this condition as simulated tumor tissue environment. This result is due to the pKa values of MTX (MTX pKa 4.8 and 5.6), which was more than of environment pH, and led to the disconnection of the ionic bonds between positive segment of NG and the MTX drugs . Under physiological conditions, only 7.8% of drug was released during 48 hours, proposing that MTX was well reserved in the NGs after the NGs were circulated.…”

“…This result is due to the pKa values of MTX (MTX pKa 4.8 and 5.6), which was more than of environment pH, and led to the disconnection of the ionic bonds between positive segment of NG and the MTX drugs. 32,33 Under physiological conditions, only 7.8% of drug was released during 48 hours, proposing that MTX was well reserved in the NGs after the NGs were circulated. Additionally, in the reduced condition (10mM GSH), a noticeably quick release of drug was identified, due to the degradation of disulfide bonds in reducing environment, exhibiting low permeation of drugs in blood vessel.…”