Green Extraction Technologies and Kombucha Elaboration Using Strawberry Tree (Arbutus unedo) Fruits to Obtain Antioxidant and Anti-Inflammatory Fractions

Abstract

The fruits of Arbutus unedo (strawberry tree, ST) have been widely used for culinary and medicinal purposes because of their content in phenolic compounds and other bioactives. The aim of this study was to apply green technologies using water as solvent to obtain phenolic-rich fractions from ST fruits. Moreover, a kombucha beverage (KOM) using these fruits as substrate was prepared. Conventional (cold and hot water extractions) and advanced (ultrasound- and microwave-assisted-extractions) protocols were carried out, leading to fractions with high total phenolic content (TPC), up to 40.72 mg/100 mL in a microwave extract (MHWE), with also 7.89 mg total carbohydrates/mL and 106.12 µg soluble proteins/mL. Moreover, the kombucha showed even higher TPC (70.99 mg/100 mL). Biological activities were also tested for all the fractions, registering the highest antioxidant activity for KOM (2.63 and 6.22 µmol/mL of TEAC value as DPPH• scavenger and cellular antioxidant activity, respectively) and MHWE (2.76 µmol/mL of TEAC value). Strong correlations were observed between TPC or specific compounds (mainly catechin derivatives) and antioxidant activity. Furthermore, KOM and the aqueous extracts were able to reduce pro-inflammatory cytokines (TNF-α, IL-1β, IL-6) in a cellular model.