Extração de compostos ativos do resíduo borra de café empregando solvente eutético natural profundo (NADES)

Abstract

This study examines the increasing generation of solid waste and its environmental implications, focusing on coffee grounds discarded by industries during the processing of coffee beans. Although typically considered waste, coffee grounds possess significant antioxidant, antitumor, anti-inflammatory, and antiallergic properties. In this sense, the main objective of this work was to extract bioactive compounds from coffee grounds using solid-liquid extraction employing Natural Deep Eutectic Solvent (NADES) and ultrasound. For this purpose, a NADES100 composed of choline chloride and lactic acid was prepared, along with two dilutions of it with 10% and 20% (v/v) of distilled water, named NADES90 and NADES80. The extraction of bioactive compounds was performed using 5 different solvents: NADES100, NADES90, NADES80, PA ethanol, and distilled water. These solvents separately and in triplicate were added to the dried and standardized coffee grounds at a ratio of 5% (m/v) of solution, then Falcon tubes containing the coffee ground/solvent mixture were inserted into an ultrasonic bath. After extraction, centrifugation was performed to separate the solid residue from the extract containing the bioactive compounds extracted by the solvents. The extracts were analyzed to evaluate antioxidant capacity by the FRAP+ and DPPH methods, total phenolic compounds by the Folin-Ciocalteu method, and total flavonoids. Each analysis used calibration curves with Trolox, gallic acid, and quercetin standards, according to the methodology described in the literature. The results were statistically evaluated by analysis of variance (ANOVA), followed by Tukey's test to identify significant differences between the extracts. After analyzing the results, it was concluded that NADES and ultrasound were efficient for the extraction of bioactive compounds from coffee grounds. Interestingly, water and ethanol stood out, demonstrating unexpected performance, which can be explored in the future in other studies. Therefore, it is suggested that the use of this green, environmentally friendlier solvent may be an interesting alternative for such a process, since the NADES solvent proved to be as effective as ethanol and water, equalizing its potential for this application.