Abstract: In this study, the changes of phenolic contents and antioxidant activities were explored during the in vitro digestion of whole kiwiberry fruit, free phenolic extract and pomace from four cultivars. Total phenol contents (TPC) before and during the digestion process were determined by Folin-Ciocalteu method. Qualitative and quantitative analysis of individual phenolics by ultra-high performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS) and high performance liquid chromatography coupled with photo-diode array-mass spectrometry (HPLC-PDA-MS). The effect of gastrointestinal digestion was determined on the antioxidant activity of kiwiberry as evaluated by peroxyl radical scavenging capacity and cellular antioxidant activity (CAA) assays. The results showed that total phenol contents in whole fruit and free phenolic extract exhibited the same trend during in vitro digestion: raw > mouth > stomach > small intestine. Total phenol contents in pomace showed a different trend: small intestine > stomach > raw > mouth. At different digestion stages, gastric (low pH) and intestinal environments (high pH) had different effects on the stability of phenolic compounds, causing degradation or transformation of phenolic compounds, and the structure of phenolic compounds itself could also affect their degradation and transformation. Since phenolic compounds were the main antioxidants in kiwiberry fruit, peroxyl radical scavenging capacity and phenolic contents showed consistent trends with each other during in vitro digestion. The results of this research may provide a scientific basis for the development and application of natural products from kiwiberry fruit.

Key words: kiwiberry; phenolic compound; phenolic acid; antioxidant activity