Polyphenol Content and Bioactivity of Pomegranate Peel and Their Cultivar and Environment Dependencies

Phenolics contents and in vitro bioactivities of 10 pomegranate peels and their cultivar and environment dependencies were investigated. The results showed total free polyphenol contents of the peels ranged in 104.17-200.91 mg GAE/gDW, which were 10-12 folds more than total bound ones and punicalagins B was predominant component of them. Total free phenolic content of pomegranate peel were significantly different among some cultivars and all produce regions which have significant different environment, significantly positively correlated with total sunlight time and negatively with total precipitation and average temperature in fruit mature period. They were significantly positively correlate with DPPH• scavenging capacity, ABTS+• scavenging capacity, total reducing power and total antioxidant capacity of the peels. The purified phenolic extracts could induce Caco-2 cells apoptosis in vitro in dose dependent manner and through multiple cell signaling pathways. In conclusion, phenolic content of pomegranate peel depend on both cultivar and meteorological condition. Antioxidant and antiproliferative activities of pomegranate peel extract positively correlate with its total phenolic content.