Resveratrol is a phytoalexin produced naturally by several plants when under attack by bacteria or fungi. Phytoalexins are antibacterial and anti-fungal chemicals produced by plants as a defense against infection by pathogens. Resveratrol has also been produced by chemical synthesis,[1] and is sold as a nutritional supplement derived primarily from Japanese knotweed. A number of beneficial health effects, such as anti-cancer, antiviral, neuroprotective, anti-aging, and anti-inflammatory effects have been reported, but all of these studies are "in-vitro" (test tube) or in yeast, worms, fruit flies, fish, mice, and rats. Resveratrol is found in the skin of red grapes and is a constituent of red wine but, based on extrapolation from animal trials, apparently not in sufficient amounts to explain the "French paradox" that the incidence of coronary heart disease is relatively low in southern France despite high dietary intake of saturated fats.[2]
The four stilbenes cis- and trans-resveratrol, and their glucosides cis- and trans-piceid are sometimes analyzed together as a group.[3]
"All of the muscadine table wines sampled had greater trans and cis resveratrol concentrations than any other wines sampled. The muscadine table wines varied between 9.2 and 31.9 mg/L cis-resveratrol and between 4.9 and 13.4 mg/L trans-resveratrol."[3]
| Beverage | Total resveratrol (mg/L)[8][3] |
Total resveratrol
in a 5 ounce glass (mg)[8][3] |
|---|---|---|
| Muscadine Wines | 14.1 - 40 | 2.12 - 6 |
| Red Wines (Global) | 1.98 - 7.13 | 0.30 - 1.07 |
| Red Wines (Spanish) | 1.92 - 12.59 | 0.29 - 1.89 |
| Red grape juice (Spanish) | 1.14 - 8.69 | 0.17 - 1.30 |
| Rose Wines (Spanish) | 0.43 - 3.52 | 0.06 - 0.53 |
| Pinot Noir | 0.40 - 2.0 | 0.06 - 0.30 |
| White Wines (Spanish) | 0.05 - 1.80 | 0.01 - 0.27 |
The trans-resveratrol concentration in 40 Tuscan wines ranged from 0.3 to 2.1 mg/L in the 32 red wines and had a maximum of 0.1 mg/L in the 8 white wines tested. Both the cis- and trans-isomers of resveratrol were detected in all tested samples. cis-Resveratrol levels were comparable to those of the trans-isomer. They ranged from 0.5 mg/L to 1.9 mg/L in red wines and had a maximum of 0.2 mg/L in white wines.[12]
Reports suggest that some aspect of the wine making process converts piceid to resveratrol in wine, as wine seems to have twice the average resveratrol concentration of the equivalent commercial juices.[3]
"All of the muscadine table wines sampled had greater trans and cis resveratrol concentrations than any other wines sampled. The muscadine table wines varied between 9.2 and 31.9 mg/L cis-resveratrol and between 4.9 and 13.4 mg/L trans-resveratrol."[3]