Effect of extraction solvent and various drying methods on polyphenol content and antioxidant activities of yuzu (Citrus junos Sieb ex Tanaka)

The effects of different extraction solvents (water, EtOH, MeOH, acetone, DMSO, and their mixture) and various drying methods (air, oven, microwave, and freeze drying) were investigated on total polyphenol content (TPC), total flavonoid content (TFC) and antioxidant activity of peel, pulp, and seeds of yuzu fruit. Mixed solvents exhibited better results compared to the absolute solvents. 50 % acetone exhibited the highest FRAP and CUPRAC value in peel and pulp and TPC in seeds of yuzu fruits. 80 % acetone which also gave nearly similar results with 50 % acetone (p > 0.05) showed the highest TPC in peels and pulp and highest CUPRAC values in seeds. Absolute acetone was the least desirable solvent employed for extraction in most of the samples. Drying methods also significantly affected the total polyphenols content, total flavonoid content and antioxidant potential of yuzu fruits. Oven drying resulted in declines of the TPC, TFC, FRAP, DPPH, and CUPRAC from 0.2 to 33.0 % relative to fresh samples while air drying resulted a decrease in the range between 2.5 and 30.6 %. Freeze dried samples showed the highest percent retentions of polyphenols content, flavonoid content, and antioxidants (70.6-122.1 %). Drying methods caused the highest loss of TPC, TFC, FRAP, and CUPRAC in pulp samples except DPPH radical scavenging activity. In overall, the extraction of secondary metabolites and antioxidants was highly dependent on the extraction solvent, type of sample and sample processing methods.