Solubilities prediction of ginger bioactive compounds in liquid phase of water by the COSMO-RS method

The solubilities in water of four main ginger bioactive compounds, 6-gingerol, 6-shogaol, 8-gingerol and 10-gingerol, were predicted using a conductorlike screening model for real solvent (COSMO-RS) calculations. This study was conducted since no experimental data are available for ginger bioactive compounds solubilities in liquid phase of water. The s-profiles of these selected molecules were calculated using Gaussian software and the solubilities were calculated using the COSMO-RS method. The solubilities of these ginger bioactive compounds were calculated at 50–200 °C. In order to validate the accuracy of the COSMO-RS method, the solubilities of five hydrocarbon molecules were calculated using the COSMO-RS method and compared with the experimental data in the literature. The selected hydrocarbon molecules were 3-pentanone, 1-hexanol, benzene, 3-methylphenol and 2-hydroxy-5-methylbenzaldehyde. The calculated results of the hydrocarbon molecules are in good agreement with the data in the literature. These results confirm that the solubilities of ginger bioactive compounds can be predicted using the COSMORS method. The solubilities of the ginger bioactive compounds are lower than 1.0 × 10-4 at temperatures lower than 130 °C. At 130–200 °C, the solubilities increase dramatically with the highest being 6-shogaol, which is 3.7 × 10-4 mole fraction, and the lowest is 10-gingerol, which is 0.39 × 10-4 mole fraction at 200 °C

Effect of sonication on the dielectric constant of water and water + ethanol in ginger extraction

The dielectric constant of solvents and solutes play important role to the extraction efficiency of a process through the ability of solutes to dissolve in solvent. The dielectric constant of water can be manipulated by introducing some external interventions such as temperature, entrainer and sonication. A lot of studies have been done on the effect of high temperature in decreasing the dielectric constant of water to 27 at 250oC [1, 2] to act as organic solvent. In this study, we are focusing on the lower temperature (25 – 55 oC) with ethanol as entrainer and sonication to decrease the dielectric constant of water. There were four major bioactive compounds from ginger extraction which were 6-gingerol, 8-gingerol, 10-gingerol and 6-shogaol. Those bioactive compounds were non-polar with slightly polar [3]. Distilled water and ethanol (95%, AR, J. Kollin Chemicals) were used to prepare the solvent mixtures. The dielectric constant of solvent was measured using Alpha TDR-5000 (Zadow Electronics, Germany) and the dielectric constant of solvent and ginger extraction was measured using Agilent 85070B dielectric probe with Network Analyzer (USA). The dielectric constant of distilled water decreases from 70.81 at 25oC to 66.10 at 55oC with sonication (28kHz, 100% power). Ethanol was added as the entrainer to decrease the dielectric constant of the solvent. As the percentage of ethanol increase from 5% to 30%, the dielectric constant also decreases. At 55oC, the dielectric constant of 5% ethanol in water was 66.10 and decreases as the percentage of ethanol increases to 30% with the dielectric constant of 58.29. The same trends were also shown as the temperature increases. Next, the polarities of water and water+ethanol with the present of ginger for ultrasonic extraction were studied. The results show different trends compared to without ginger presents which are almost the same trend as reported by [4]. The interaction of ginger with the solvent mixtures changed the dielectric constant of the mixtures. The dielectric constant of solvent mixtures and ginger lower than without ginger, but increased as the temperature increased. This can be explained by the solvation phenomena and disrupts the interaction between molecules in increasing the solubility and extraction efficiency

Estimation of ginger bioactive compound solubilities in hot compressed water and enhancement with entrainer

Knowledge concerning the solubility of ginger bioactive compounds in hot compressed water (HCW) is important for designing an extraction process with water as a green solvent. The solubilities of 6-gingerol and 6-shogaol in hot compressed water are calculated using the conductor-like screening model for real solvent (COSMO-RS) method to study the potential of water as a solvent. The comparison indicates that the calculated solubility is at a higher concentration for the binary system of 6-gingerol. +. water and 6-shogaol. +. water when compared to the HCW extraction. This illustrates the performance of the HCW extraction, which has not reached the equilibrium condition, and gives an opportunity to explore the options for further improving the process. The availability as well as the thermo-labile nature of the bioactive compounds are factors that must be considered for the improvement of HCW as a solvent. The solubilities of 6-gingerol and 6-shogaol in aqueous ethanol solutions are also calculated by the COSMO-RS method to study the entrainer effect of ethanol. The calculations with ethanol as entrainer indicate that the molecular cavity and contact interaction are changed so as to increase the solubilities. Based on the calculations, the suitable amount of ethanol as an entrainer is estimated to be 0.02. mole fraction for both 6-gingerol and 6-shogaol with an improved solubility of 1.86 and 1.76 times, respectively. In general, the addition of the entrainer will improve the recovery and operating parameters at a milder operating condition. This approach may be applied to other bioactives and will further strengthen the use of water as a solvent in natural extract