Supercritical and subcritical extraction of ursolic acid and polyphenols from apple pomace: Effect of variables on composition and antioxidant capacity

This research explores the effect of temperature, pressure, static time, dynamic time, co-solvent, pretreatment, and particle size on the supercritical/subcritical extraction of ursolic acid (UA), polyphenols, and their antioxidant activity. Experiments were controlled by a screen-out (Plackett–Burman) statistical methodology. From the results, it could be observed that similar conditions benefited the extraction of UA and polyphenols. The highest yield of UA (6,117.2 µg/g) was obtained when ethanol (25% w/w), particle size (>250 µm), and temperature (60°C) were at their high boundaries. Phloridzin and epicatechin were identified as the most abundant polyphenols, showing concentrations of 531.4 and 288.3 µg/g, respectively. A maximum oxygen radical absorbance capacity of 113.5 µmol TE/g and total polyphenolic capacity (TPC) of 1.7 mg GAE/g were obtained. As a result, higher yields were strongly related to the effect of variables on diffusion and solubility, leading to a more efficient and sustainable process. Practical applications There is always a need to develop efficient and environmentally friendly extraction processes. It is well known that most of the conventional extraction methods are solvent intensive, time-consuming, and require multistep. Supercritical extraction has demonstrated to be a feasible nonconventional extraction method. However, before scaling, it is essential to screen-out critical variables among the set of variables available. The extraction of ursolic acid (UA) and polyphenol fractions from apple pomace has the potential for their application in the food and pharmaceutical industry. The current research evaluates the effect of seven variables in the extraction of UA, polyphenols, and their antioxidant capacity from apple pomace. The information here presented aids in understanding which variables are more important for the extraction process.