Effect of in vitro digestion on hydrophilic and lipophilic antioxidant capacity of commonly consumed fruits and vegetables

Raw consumed fruits and vegetables are the main sources of dietary antioxidants as bioactive food components. The aim of this study was to compare the hydrophilic and lipophilic antioxidant activity of fruits and vegetables after in vitro digestion. For this purpose, the hydrophilic and lipophilic fractions of these foods were isolated and then in vitro digestion was performed. The Folin-Ciocalteu method, a 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity assay, and a Trolox equivalent antioxidant capacity (TEAC) assay were used herein. A comparison of the antioxidant activities before and after in vitro digestion revealed that digestion appeared to increase the antioxidant -capacity of the lipophilic fractions, whereas no such increase occurred in the hydrophilic fractions. For the hydrophilic fraction, the total phenolic content of the tested fruits and vegetables was in the range of 0.02-0.44 g kg(-1) after gastric digestion, and it was 0.010.34 g kg-1 after duodenal digestion. For the lipophilic fraction, it ranged from 0.01 to 5.07 g kg(-1) after gastric digestion and 0.06 to 3.97 g kg(-1) after duodenal digestion. For the hydrophilic fraction, the total antioxidant capacity of the tested fruits and vegetables was in the range of 18.7-31.5% after gastric digestion and it was 21.0-39.9% after duodenal digestion. For the lipophilic fraction, it ranged from 26.8 to 93.7% after gastric digestion and 49.0 to 92.2% after duodenal digestion. The majority of the fruits and vegetables tested showed significantly increased antioxidant activities after in vitro digestion, when compared to their initial value.