Abstract: Phenolics widely exist in plants in free, esterified, and insoluble bound forms. The aim of the present study was to evaluate the changes in phenol contents, antioxidant and in vitro cytoprotective activities against H2O2 induced oxidative damage on HepG2 cells of free, esterified and insoluble bound phenolics in the peel of Passiflora edulis Sims (PEP) after ultra-high pressure (UHP) pretreatment. The results showed that after UHP treatment, not only the extraction rates of free, esterified and insoluble bound phenolics, but also the free phenol and flavonoid contents in the three phenolic extracts significantly increased. However, the phenol contents in the esterified and insoluble bound phenolic extracts significantly decreased. In addition, the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical and 2,2’-azino-bis (3-ehtylbenzothiazoline-6-sulfonic acid) (ABTS) radical cation scavenging capacity and ferric reducing antioxidant power (FRAP) of free phenols from the UHP treated PEP were significantly higher than those of the untreated PEP group, and the antioxidant capacity of all phenolic fractions was positively correlated with the phenol contents. The results of intracellular reactive oxygen species (ROS) and apoptosis assay showed that there was little difference in the ROS scavenging capacity or apoptosis between each phenolic fraction and the positive control group (VC). In summary, UHP pretreatment can effectively increase the phenol content, flavonoid content and antioxidant capacity of free phenolic fraction from Passiflora edulis peel, which could be used in functional foods and nutraceuticals thereby improve its application and economic value.

Key words: Passiflora edulis Sims; antioxidant; cell; reactive oxygen species; apoptosis