Measurement and thermodynamic functions of solid–liquid phase equilibrium of d-(−)-quinic acid in H2O, methanol, ethanol and (H2O + methanol), (H2O + ethanol) binary solvent mixtures

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Highlights

  • Solubility of d-(−)-quinic acid in pure and binary solvents was determined.

  • The solubility data were fitted using four models.

  • Good correlation was existed between experimental and calculated solubilities.

  • Results showed that the Apelblat model superior to the λh, Wilson and NRTL model.

  • The Gibbs free energy, enthalpy, entropy were calculated by the van’t Hoff analysis.

Abstract

The solubility of d-(−)-quinic acid in H2O, methanol, ethanol and (H2O + methanol), (H2O + ethanol) binary solvent mixtures was measured at temperatures from (298.15 to 328.15 or 348.15) K by using the HPLC method under atmospheric pressure. The experimental values indicate that the solubility of d-(−)-quinic acid in the binary mixed solvents increases with the increasing temperature and decreases with the rise of molar concentration of organic solvents. The Apelblat model, λh model, Wilson model and NRTL model were used to correlate the experimental results and the relative average deviation (RAD) between the experimental and calculated values is less than 0.0358, 0.0421, 0.0359 and 0.0397 for the Apelblat model, λh model, Wilson model and NRTL model, respectively. Furthermore, thermodynamic properties of the solution process, including the Gibbs energy, enthalpy, and entropy were also calculated and analyzed.

Introduction

d-(−)-Quinic acid ((1R,3R,4S,5R)-1,3,4,5-tetrahydroxycyclohexane-1-carboxylic acid, CASRN 77-95-2) is a cyclitol derivative, a polyol derivative shown in Fig. 1. It is a crystalline acid which is widely distributed in the leaves and fruits of dicotyledonous plants, such as fruits, coffee, cocoa beans, wine and chinchona [1]. d-(−)-Quinic acid can also be formed HPLCally by hydrolysis of chlorogenic acid [2]. Meantime it could be obtained by microbial fermentation. d-(−)-Quinic acid is one of the most important fine chemical products and intermediates of drug synthesis. It has been reported as an antioxidative [3], [4], [5], anti-inflammatory [6] and anti-mutagenic agent [7], [8] in prior studies, as well as the ability to chelate transition metals in vitro [9]. d-(−)-Quinic acid also be used as a drug carrier to solid tumours for formed quinic acid-conjugated nanoparticles which has been used to increase the distribution of a drug in tumours, thereby reducing the effective dose and nonspecific toxicity of chemotherapy [10]. Studies have shown that the d-(−)-quinic acid could decrease the DNA damage induced by X-ray irradiation and provided a significant radio protective effect. Meantime, d-(−)-quinic acid could be successfully used for the synthesis of some important quinic acid derivatives which have many applications [11], [12], [13]. d-(−)-Quinic acid and (−)-shikimic acid (another types of this compound) are key intermediates in the biosynthesis of aromatic compounds in living systems [14], [15].

The limited supply and high cost are the major reasons behind the shortage of d-(−)-quinic acid. With the worldwide rapid development, a breakthrough for higher production of d-(−)-quinic acid is necessary. We try to increase the productivity of d-(−)-quinic acid via biosynthesis, but we there is difficulty to separate the (−)-shikimic acid and d-(−)-quinic acid so we need the solubility values. However, the solubility for d-(−)-quinic acid has not been reported. More particularly, knowledge of accurate solubility is needed for the design of separation processes such as extractive crystallization and the safety of operating different processing units such as distillation columns, absorption units, and extraction plants. The solubility of d-(−)-quinic acid can also supply basic and theoretical information useful for industrial production. To determine selection of proper solvents and to design an optimized production process, it is necessary to know the solubility of d-(−)-quinic acid in different solvents. Because organic acids have high affinity for water, this leads to low distribution coefficients so that the pure organic solvents do not extract the solute. We present values of the solubility of the d-(−)-quinic acid in H2O, methanol, ethanol and (H2O + methanol), (H2O + ethanol) binary solvent mixtures measured at temperatures from (298.15 to 328.15 or 348.15) K using the HPLC method under atmospheric pressure. The Apelblat model, λh model, Wilson model and NRTL model were applied to correlate the experimental results. The thermodynamic properties of the dissolution process, including enthalpy, entropy and Gibbs energy, were calculated by means of the van’t Hoff analysis and Gibbs equation.

Section snippets

Materials

d-(−)-Quinic acid (mass fraction purity  0.98) was obtained from Shanghai vibration spectrum Biological Technology Co. Ltd. Methanol and Ethanol was analytical reagent (AR) grade, and was obtained from Sailboats Tianjin Chemical Reagent Co. Ltd, having mass fraction purities of 0.995 and 0.997, respectively. All the information about the materials used is listed in Table 1.

Characterization

Powder XRD pattern (Fig. 2) of d-(−)-quinic acid sample was used to identify its crystallinity. The patterns were obtained

Apelblat model

The relationship between mole fraction of the solubility and temperature is generally modeled as follows [20]:lnx=A+BT+ClnT,where A, B and C are empirical constants determined by fitting the experimental values T  x, x is the mole fraction of the solubility at the system temperature T. Eq. (2) is the Apelblat model.

λh model

The λh model developed by Buchowski in 1981 [21] is a semi-empirical equation, shown as follows:ln1+λ(1-x)x=λh1T-1Tm.

The λ and h are the model parameters determined from the

Characterization and identification of d-(−)-quinic acid

PXRD was used to characterize the sample before and after the experiments. The result in Fig. 2 shows that crystal forms of the solute did not change during the experiment.

Melting properties could be obtained from the differential scanning calorimetry (DSC) (Fig. 3). The instrument was calibrated by using the phase-transition temperature and phase-transition enthalpy of reference materials (and the onset temperature was chosen as the melting temperature. Indium: Tm = 429.73 K, ΔHfus = 3266.59 J·mol−1

Conclusions

This work contain the experimental results for the solubility of d-(−)-quinic acid in H2O, methanol, ethanol and (H2O + methanol), (H2O + ethanol) binary solvent mixtures at temperatures from (298.15 to 328.15 or 348.15) K which were not previously reported in the literature. Computational results showed that the calculated values show good agreement with the experimental results. It was obvious that the solubility increases with the rise of temperature and decreases with the rise of the ratio of

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