Europeans developed an ointment from the sap of grapevines to cure skin and eye diseases. Grape leaves were used to stop bleeding, inflammation, and pain, such as the kind brought on by hemorrhoids. Unripe grapes were used to treat sore throats and dried grapes (raisins) were used to heal consumption, constipation, and thirst. The round, ripe, sweet grapes, were used to treat a range of health problems including cancer, cholera, smallpox, nausea, eye infections, and skin, kidney, and liver diseases. Red grapes and red wine contain levels of flavonoids which have antioxidant properties and help to reduce the risk for cancer and heart disease. These flavonoids also have an anti-inflammatory and anti-allergic effect. Red grape leaves have been traditionally used to treat diarrhea, heavy menstrual bleeding and uterine hemorrhage.
Several epidemiological studies have shown that moderate consumption of red wine can decrease coronary heart disease mortality. Studies have shown that quercetin and other polyphenols in wine prevent oxidation. Frankel et al showed in the study entitled "Inhibition in vitro of oxidation of human low density lipoproteins by phenolic compounds in wine" published in Lancet (1993, 39:1743-1748) that red wine protects low density lipoproteins from oxidation. The flavonoids ellagic acid and resveratrol have been shown to reduce the risk of coronary heart disease.
Grape contains phenolic compounds, including resveratrol, flavon-3-ols, caffeic acid, ellagic acid and quercetin. Phenolic compounds have been correlated with the inhibition of various cancers, including colon, esophagus, lung, liver, mammary and skin cancers. Resveratrol can inhibit cancer formation in different ways: resveratrol stops DNA damage, improves DNA repair, slows down tumor growth and slows cell transformation from normal to cancerous. Jang et al demonstrated in his study "Cancer chemopreventive activity of resveratrol, a natural product derived from grapes" published in Science (1997, 275:218-220) that resveratrol has cancer chemopreventive activity in different stages of carcinogenesis. Resveratrol was found to act as an antioxidant and antimutagen and to induce phase II drug-metabolizing enzymes; it mediated anti-inflammatory effects and inhibited cyclooxygenase and hydroperoxidase functions.
Grape phenolics such as catechins, flavonols, anthocyanins and tannins have strong antioxidant activity. Grape antioxidants help to prevent the risk of several chronic and age related diseases including dementia, cancer, heart disease and cataracts.
Antibacterial and antiviral activity
A study showed that grape phenolics possess antibacterial and antiviral activities. The following phytochemicals in grape have weak antibacterial activity: hydroxybenzoic acid, salicylic acid, gallic acid and protocatechuic acid. Chlorogenic acid and epicatechin have shown antiviral activity against some viruses.