Green Processing of Ilex guayusa : Antioxidant Concentration and Caffeine Reduction Using Encapsulation by Supercritical Antisolvent Process

This study investigated the valorization of leaves by producing a low-caffeine, antioxidant-rich product through the supercritical antisolvent extraction (SAE) process. The objective was to concentrate the antioxidants while selectively reducing the caffeine. The SAE treatments were conducted using an ethanolic extract of guayusa leaves under varying pressure (80 bar-150 bar) and temperature (35-45 °C) conditions to improve the recovery of chlorogenic acid (CGA) and caffeine fractionation. The co-precipitation of antioxidants with polyvinylpyrrolidone (PVP) (ratio 1:1-1:2 mass/mass) as an encapsulant was also studied. The SAE precipitates were analyzed for their recovery yield, CGA and caffeine contents, antioxidant activity, and total phenols. Based on the statistical analysis, the optimal conditions for the SAE were 120 bar and 45 °C. Under these conditions, the CGA concentration increased from 43.02 mg/g extract to 237 mg/g precipitate, while the caffeine was reduced to less than 1% mass. Co-precipitation with PVP improved the recovery yield by more than two times than the SAE alone while maintaining the caffeine content below 1% mass. Additionally, the co-precipitation with PVP facilitated the formation of spherical microparticles, indicating successful encapsulation of the bioactive compounds, with an IC of 0.51 ± 0.01 mg/mL for DPPH and 0.18 ± 0.01 mg/mL for ABTS. These results highlight the effectiveness of the SAE co-precipitation process in developing low-caffeine functional ingredients with potential food and pharmaceutical applications.