Bioactivities and fitting models of Quercus infectoria galls extracts using supercritical carbon dioxide

Abstract

The extraction of natural plants has gained interest from the researchers due to their therapeutic values. In this study, the bioactive compounds of Quercus infectoria galls were extracted using supercritical carbon dioxide. The optimization of extraction conditions was performed using response surface methodology. The effect of extraction conditions (pressure, temperature, particle size) on extraction yield and hydrolysable tannins content of Q. infectoria were investigated. The biological properties of the extracts were evaluated by in vitro wound healing assay including total phenolic content, free radical scavenging, cell proliferation and scratch assay. The density-based models for simulation of extract solubility were also correlated. The mass transfer phenomena for extraction process of Q. infectoria galls was also investigated using both single sphere model and the broken and intact cells model. The extraction was conducted at 2 mL/min of carbon dioxide flow rate with the addition of methanol (purity: 99.8%) at ratio of 1:3 (weight of sample/volume of methanol) and was kept constant throughout this study. The study revealed that pressure, temperature and particle size were critical parameters that significantly affect the extraction yield, but did not contribute to the hydrolysable tannins content. The overall yield increased with increased pressure, temperature and particle size. The best conditions obtained from the optimization process were pressure (28.11 MPa), temperature (50.43°C) and particle size (1.25 mm) with predicted yields of 6.02%, tannic acid composition (6149.71 mg/g) and gallic acid concentration (96.85 mg/g). The galls extract showed high biological properties in terms of total phenolic content, antioxidant activity, cell proliferation and migration properties. Bartle model successfully fitted to the experimental solubility data with low absolute average relative deviation which was 1.52%. Single sphere model provides better correlation for mass transfer coefficient estimation than the broken and intact cell model. The findings from both models suggested the importance of internal diffusion and mass transfer in the extraction process of the galls.