TABLE 1.

Summary of physiological functions of pomegranate peels.

Physiological functions	Bioactive compounds	Evidences of effects
Antioxidant	Ellagitannins	• Urolithin as an antioxidant molecule, may reduce cisplatin-induced renal oxidative damage in the mice’s kidneys in vivo (51). • Pomegranate peel extracts reduce the levels of TBARS, Ox-LDL, lipid peroxidation, and oxidative biomarkers associated with cardiovascular risk in healthy volunteers (52–54).
Anti-inflammatory	Urolithins	• PPE exerted anti-inflammatory effects by significantly reducing inflammatory markers (MDA, IL-6, and hs-CRP) in obese volunteers (61). • In 2010, an in vivo study on intestinal inflammation found that Uro-A is a potent anti-inflammatory molecule (62).
Anticancer	Punicalagin, ellagic acid, ellagitannins	• Punicalagin and ellagic acid induce apoptosis in prostate cancer cells through some basic pathways, such as the introduction of cytochrome c in the cell cytoplasm, upregulation of Bax, and downregulation of Bcl-2 (64). • Urolithin B, a metabolite of ellagitannin, can inhibit testosterone-induced proliferation of MCF-7 cells associated with breast cancer (69). • Pomegranate peel extracts can inhibit the cell proliferation and the expression of angiogenic markers, and activate pro-survival signal pathways (70, 71).
Anti-bacterial	Punicalagin, ellagitannins, ellagic acid, gallic acid	• Phenolic compounds can make membrane proteins precipitated and inhibit the activity of enzymes, thus leading to bacterial death (74–77). • Punicalagin, ellagitannin, ellagic acid, and gallic acid can treat the Staphylococcus aureus and hemorrhagic Escherichia coli (78–80).
Cardiovascular protection	Polyphenols, dietary fiber	• The polyphenols and dietary fiber in pomegranate peels prevent cardiovascular disease by lowering serum total cholesterol, triglycerides, LDL, and lipid peroxidation levels (84).
Others	Punicalin, punicalagin, gallic acid, ellagic acid, urolithins	• The antiviral properties are mainly due to the polyphenol extracts inhibits the RNA replication of influenza viruses (87). • Ellagic acid and its derived metabolite urolithin may prevent or intervene in Alzheimer’s disease (89, 90).