BIOACTIVE POTENTIAL OF PHENOLIC EXTRACTS FROM COFFEE SILVERSKIN (Coffea arabica): PHENOLIC PROFILE AND ANTIOXIDANT AND HYPOGLYCEMIC ACTIVITIES

The coffee production chain has significant economic relevance and generates different by-products throughout processing. Among them, coffee silverskin is detached during bean roasting and, despite its continuous generation by the coffee industry, remains underutilized. Its valorization represents an alternative for the recovery of compounds of biological and technological interest, considering its diverse chemical composition and the presence of constituents associated with bioactive properties. In this context, this study aimed to evaluate the bioactive potential of phenolic extracts from coffee silverskin (Coffea arabica), with emphasis on the phenolic profile and antioxidant and hypoglycemic activities. Three extracts were obtained using water (ES100), water:ethanol 80:20 (v/v) (ES80), and water:ethanol 50:50 (v/v) (ES50), through extraction at 60 °C for 60 min, followed by centrifugation and filtration. The phenolic compound profile was determined by high-performance liquid chromatography with diode-array detection (HPLC-DAD), based on comparison with analytical standards and external calibration curves. Antioxidant activities were evaluated using the DPPH, ABTS, and FRAP assays, while hypoglycemic potential was assessed by α-amylase inhibition. HPLC-DAD characterization revealed significant differences among the extracts, demonstrating the selectivity of the extraction systems in recovering the compounds. ES100 was characterized by higher representation of vanillic acid, caffeic acid, and chrysin; ES80 by epicatechin, syringic acid, myricetin, ferulic acid, and quercetin; whereas ES50 stood out for 4-hydroxybenzoic acid, salicylic acid, gallic acid, p-coumaric acid, catechin, and caffeine. The distinct profiles may be related to changes in medium polarity with increasing ethanol proportion. Due to its higher polarity, water favors the solubilization of more polar constituents, whereas the presence of ethanol may enhance the extraction of compounds with intermediate polarity, resulting in different phenolic combinations. This selectivity demonstrates that the choice of extraction system can influence the chemical composition of the extract and, consequently, its application potential, since different compounds may contribute differently to the bioactive properties observed. Regarding antioxidant activity, ES50 showed the highest responses in the DPPH, ABTS, and FRAP assays, with 3.01 ± 0.72, 1.73 ± 0.07, and 3.87 ± 0.12 µmol Trolox equivalents/100 mL, respectively. For α-amylase inhibition, ES50 (51.765%) and ES80 (47.647%) showed greater activity than ES100 (40.824%), with no significant difference between ES50 and ES80. Overall, the results demonstrate that the composition of the extraction system influences the phenolic profile and bioactivities of the extracts, with ES50 exhibiting the most favorable combination of characteristics. Thus, coffee silverskin (Coffea arabica) shows potential as a source of bioactive compounds for the development of functional ingredients and the valorization of coffee industry by-products.

Acknowledgments: CAPES.