Non-extractable polyphenols from cranberries: potential anti-inflammation and anti-colon-cancer agents

Abstract

Cranberries (Vaccinium macrocarpon) are full of polyphenols, which display various health benefits. Most studies have focused on extractable polyphenols (EPs) rather than non-extractable polyphenols (NEPs) but NEPs may possess important biological functions. The objective of this work was to characterize EP and NEP fractions from whole cranberries and determine their potential as anti-inflammation and anti-colon-cancer agents. Our results showed that of the identified polyphenols, anthocyanins were the major ones in the cranberry EP fraction, while phenolic acids were most abundant in the NEP fraction. The oxygen radical absorbance capacity (ORAC) of the NEPs was significantly higher than that of the EPs. Both the EPs and NEPs showed anti-inflammatory effects in inhibiting LPS-induced production of nitric oxide in macrophages. At the concentrations tested, the NEPs showed significantly higher inhibition of the production of nitric oxide in macrophages than the EPs, which was accompanied by decreased expression of inducible nitric oxide synthase (iNOS) and increased expression of HO-1. EP and NEP samples showed anti-cancer capacities in HCT116 cells. And the NEPs showed stronger inhibitory effects on the viability and colony formation capacity of human colon cancer HCT116 cells than the EPs. In a flow cytometry analysis, the NEPs caused cell cycle arrest at the G0/G1 phase and induced significant cellular apoptosis in colon cancer cells. Overall, our results suggested that both the EP and NEP fractions from cranberries were bioactive, and importantly, the NEP fraction showed promising anti-inflammation and anti-colon-cancer potential.