Optimization and comparison of nonconventional extraction techniques for soluble phenolic compounds from brocade orange (Citrus sinensis) peels.

Brocade orange (Citrus sinensis L. Osbeck) peels (BOPs) are rich in a variety of phenols with multiple and strong bioactivities. This study sought to utilize a response surface methodology to optimize the parameters of accelerated solvent extraction (ASE) to obtain phenolic extracts from BOPs. Total phenolic and flavonoid content (TPC and TFC), profiles, and antioxidant activities of extracts for free, esterified-, and glycosylated-bound phenols from ASE were compared with those derived from Soxhlet extraction (SE) (80°C, 6 h) and heat-reflux extraction (HRE) (80°C, 3 h). Maximum practical TPC and TFC under optimal ASE conditions (15 min, 108°C, 82 bar, and three cycles) were determined to be 32.82 mg gallic acid equivalents/dry weight (DW) and 10.25 mg rutin equivalents/DW, respectively. The profiles, contents, and corresponding bioactivities of the extracts significantly depended on extraction method, particularly with regard to phenolic fraction. Generally, ASE and HRE were associated with higher levels of extraction efficiency and higher quality targeted bioactive compounds with stronger antioxidant activity. More importantly, ASE represents a simple, efficient, and time-saving technique for the extraction of phenols. Furthermore, the finding that different phenolic fractions contain variable profiles and contents of phenols is useful for efforts to obtain targeted individual bioactive ingredients and make better use of biomass residues.