Development of a Pressurized Green Liquid Extraction Procedure to Recover Antioxidant Bioactive Compounds from Strawberry Tree Fruit (Arbutus unedo L.)

Abstract

Strawberry tree fruits (Arbutus unedo L.) are a natural source of valuable biologically active compounds. Therefore, the aim of this work was to develop a green extraction approach using pressurized liquid extraction (PLE) to provide the highest yield of bioactive compounds. Different extraction solvents (distilled water, 50% and 96% ethanol) and different PLE parameters were investigated: temperature (40, 80, and 120 °C), static extraction time (5 and 10 min), and number of cycles (1 and 2). Total phenolic contents (TPC), hydroxycinnamic acids (HCA), flavonols (FL), total flavonoids (TF), condensed tannins (CT), and antioxidant capacity (DPPH and FRAP) were determined in PLE extracts. Solvent type, temperature, static extraction time, and number of cycles had a statistically significant effect on all bioactive compounds and antioxidant capacity (p ≤ 0.05). All bioactive compounds were positively correlated with temperature, except for TPC and DPPH. For all polyphenols studied, the optimal PLE parameters were a temperature of 120 °C, a static extraction time of 10 min and 2 cycles. The best solvent for most bioactive compounds was 96% ethanol, except for TPC, for which 50% ethanol was better. This study suggests that PLE is a promising tool to intensify the extraction of bioactive compounds from strawberry tree fruits.

Keywords: antioxidant capacity; green extraction; optimization; phenolic compounds; pressurized liquid extraction (PLE); strawberry tree fruit.

Figure 1

The impact of PLE operating conditions on examined polyphenols: (a) TPC-total phenolic content (mg 100 g⁻¹); (b) HCA-hydroxycinnamic acids (mg 100 g⁻¹); (c) FL-flavonols (mg 100 g⁻¹); (d) TF-total flavonoids (mg 100 g⁻¹); and (e) CT-condensed tannins (mg 100 g⁻¹).