Polyphenol characterization, anti-oxidant, anti-proliferation and anti-tyrosinase activity of cranberry pomace

Background: Cranberry pomace (CP), an underutilized by-product from juice processing, contains a wide range of biologically active compounds that can be recovered and used in a variety of applications in functional foods and nutraceuticals. Methods: In this study, analytical chemical techniques such as solvent extractions and characterization of extracts in respect with their phenolic content were performed using ultra-high performance liquid chromatography mass spectrometry (UPLC-MS) and spectrophotometry. Crude CP extract and its phenolic acids, flavonols, anthocyanins and proanthocyanidins–rich fractions were then evaluated for their anti-oxidant capacity, tyrosinase inhibitory activity, and anti-proliferation activity against hepatocellular carcinoma HepG2 cells. Results: On a dry weight basis, the different CP fractions contained seven major anthocyanins (0.1-125 mg/g), six major phenolic acids (0.8-31 mg/g), seven flavonols (1-126 mg/g) and five flavan-3-ols (0.1-12 mg/g). Fractions rich in flavonols exhibited the most potent antioxidant capacities with ferric ion reducing antioxidant power values of 1.8-1.9 mmole/g and 2, 2-diphenyl-1-picrylhydrazyl radical scavenging IC50 values of 15.1-15.2 mg/L respectively. On the other hand, fractions rich in phenolic acids and flavan-3-ol monomers demonstrated the most potent anti-tyrosinase activity (IC50=6.1-6.2 mg/L) and anti-proliferative activity (IC50=7.8-15.8 mg/L). Generally, all the fractions exhibited a dose-response relationship in the selected biological activity assays.Conclusion: This study suggests an effective utilization of CP to obtain biologically active fractions with potential to be used in functional foods and nutraceuticals designed for the prevention of chronic diseases associated with oxidative stress.Keywords: cranberry pomace, polyphenol, anti-tyrosinase, anti-proliferation, nutraceuticals, functional foods