Pomegranate fruit is known to have high content of flavonoid and anthocyanidin antioxidants. Fresh pomegranate juice has 0.2 - 1% soluble polyphenolic flavonoids. Further more, Fresh pomegranate juice contains 85% water, 10% total sugars, and 1.5% pectin, and ascorbic acid. Pomegranate seeds are a rich source of dietary fiber, pectin, and sugars. Dried pomegranate seeds contain the steroid estrogen estrone and phytoestrogens genistein, daidzein, and coumestrol. Pomegranate also contains amino acidssuch as glutamic and aspartic acids. Polyphenol flavonoids in pomegranate include catechins, ellagic tannins, and gallic and ellagic acids. The antioxidant composition and capacity may vary between pomegranate juice, peel and seeds. A study reported a higher antioxidant activity in the peel than the juice of pomegranate.

Because of the antioxidants, pomegranate juice, seeds, and peels have been shown to exhibit free-radical scavenging activity. Research on its antioxidant capacity and benefit against free-radical induced diseases such as cancer and neurodegenerative damage and aging corroborate its significance as a rich source of antioxidants and its role against various diseases.

Pomegranate juice, because of its antioxidant activity, was reported to have protective effect against oxidation of nitric oxide, a molecule that relaxes bloods vessels and improves blood circulation.

In a study on patients with carotid artery stenosis and subjected to three years of pomegranate juice, in a period of one year, patients experienced increased antioxidant status in the blood, decreased systolic blood pressure, and decreased copper-ion induced oxidation of serum low-density lipoprotein (LDL).

In another study, pomegranate juice consumption decreased LDL susceptibility to aggregation and retention and increased the activity of serum paraoxonase (a molecule that can protect against lipid peroxidation) by 20%.


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References:
Ignarro LJ, Byrns RE, Sumi D, de Nigris F, and Napoli C . 2006. Pomegranate juice protects nitric oxide against oxidative destruction and enhances the biological actions of nitric oxide. Nitric Oxide. 2006 Apr 18.

Aviram M, Dornfeld L, Rosenblat M, Volkova N, Kaplan M, Coleman R, Hayek T, Presser D, and Fuhrman B. 2000. Pomegranate juice consumption reduces oxidative stress, atherogenic modifications to LDL, and platelet aggregation: studies in humans and in atherosclerotic apolipoprotein E-deficient mice. Am J Clin Nutr. 71(5):1062-76.

Kelawala NS, and Ananthanarayan L. 2004. Antioxidant activity of selected foodstuffs. Int J Food Sci Nutr. 55(6):511-6.