Extraction and modelling of catechin from arachis hypogea skin using modified supercritical carbon dioxide

Abstract

Peanut skin, which contains a high level of catechin, is removed as waste in peanut industry. Catechin is well-known for its antioxidant activity. In this study, modified supercritical carbon dioxide (SC-CO2) extraction assisted by ethanol was performed to extract catechin from peanut skin. Modified SC-CO2 extraction was carried out at various experimental conditions. The effects of pressure, temperature and ratio of modifier on the extraction yield, catechin and antioxidant activity were investigated by using the response surface methodology (RSM). Three established solubility models, including the Chrastil, the Del Valle Aguilera and Adachi Lu models were applied to describe the solubility behaviour. However, the formulation of a new solubility-based model is needed to adapt the presence of ethanol as a modifier. There were two new models, namely Well-Mix (W-M) and Unwell-Mix (U-M) models, proposed in this study with the assumption of significant solubility enhancement being promoted by the addition of ethanol. Furthermore, the capability of W-M and U-M models were examined by fitting the published solubility data of Areca catechu, Rosehips and Avocado seeds. The maximum extraction yield (15.34%), catechin concentration (156.40 µg/gextract) antioxidant activity (95.99%) were obtained at 25.24 MPa, 60.83°C and 6.95 v/v% of modifier, respectively. It is proven that the effect of pressure and ratio of modifier were the significant factors required to achieve high yield extract, whereas the temperature and ratio of modifier effect gave the significant impact to obtain high catechin concentration and antioxidant activity. The W-M model offered the best fitting among all the models to correlate the solubility data of peanut skin extract with the lowest percentage of average absolute relative deviation (%AARD) of 4.20% and high coefficient of determination (R2) of 0.976 achieved. The coefficient values of ??1(????2) and ??2(????-????) were 0.716 and 0.076, respectively. It is hence believed that the solvation power of SC-CO2 was higher than ethanol to increase the solubility of peanut skin extract. Furthermore, the endothermic reaction was reported, where the solubility of solute increased with the temperature. It is also confirmed that the new models (W-M and U-M) demonstrate a good capability to fit the solubility data of Areca catechu, Rosehips and Avocado seeds as low average percentage of AARD (<15%) and high R2 (> 0.8) were reported. The results of this study reveal that peanut skin is a potential source for pharmaceutical compounds and the new models could predict successfully the solubility of the solid solute in SC-CO2 with the addition of modifier.