Resveratrol was originally isolated by Takaoka from the roots of white hellebore in 1940, and later, in 1963, from the roots of Japanese knotweed. However, it attracted wider attention only in 1992, when its presence in wine was suggested as the explanation for cardioprotective effects of wine.
In grapes, resveratrol is found primarily in the skin, and — in muscadine grapes — also in the seeds. The amount found in grape skins also varies with the grape cultivar, its geographic origin, and exposure to fungal infection. The amount of fermentation time a wine spends in contact with grape skins is an important determinant of its resveratrol content.
The levels of resveratrol found in food varies greatly. Red wine contains between 0.2 and 5.8 mg/L, depending on the grape variety, while white wine has much less — the reason being that red wine is fermented with the skins, allowing the wine to absorb the resveratrol, whereas white wine is fermented after the skin has been removed. A number of reports have indicated that muscadine grapes may contain high concentrations of resveratrol and that wines produced from these grapes, both red and white, may contain more than 40 mg/L. However, subsequent studies have found little or no resveratrol in different varieties of muscadine grapes.
The fruit of the mulberry (esp. the skin) is a source, and sold as a nutritional supplement.
The trans-resveratrol concentration in forty Tuscan wines ranged from 0.3 to 2.1 mg/L in the 32 red wines tested and had a maximum of 0.1 mg/L in the 8 white wines in the test. 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.
In a review of published resveratrol concentrations, the average resveratrol concentration in red wines is 1.9 ± 1.7 mg trans-resveratrol/l (8.2 ± 7.5 µM), ranging from non-detectable levels to 14.3 mg/l (62.7 µM) trans-resveratrol. Levels of cis-resveratrol follow the same trend as trans-resveratrol.
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.
In general, wines made from grapes of the Pinot Noir and St. Laurent varieties showed the highest level of trans-resveratrol, though no wine or region can yet be said to produce wines with significantly higher resveratrol concentrations than any other wine or region.
| Food | Serving | Total resveratrol (mg) |
|---|---|---|
| Peanuts (raw) | 1 c (146 g) | 0.01 - 0.26 |
| Peanuts (boiled) | 1 c (180 g) | 0.32 - 1.28 |
| Peanut butter | 1 c (258 g) | 0.04 - 0.13 |
| Red grapes | 1 c (160 g) | 0.24 - 1.25 |
Ounce for ounce, peanuts have about half the amount of resveratrol as that found in red wine. The average amount of resveratrol in one ounce of peanuts in the marketplace (about 15 whole) is 79.4 µg/ounce.
In comparison, some red wines contain approximately 160 µg/fluid ounce.Resveratrol was detected in grape, cranberry, and wine samples. Concentrations ranged from 1.56 to 1042 nmol/g in Concord grape products, and from 8.63 to 24.84 micromol/L in Italian red wine. The concentrations of resveratrol were similar in cranberry and grape juice at 1.07 and 1.56 nmol/g, respectively.
Blueberries have about twice as much resveratrol as bilberries, but there is great regional variation. These fruits have less than ten percent of the resveratrol of grapes. Cooking or heat processing of these berries will contribute to the degradation of resveratrol, reducing it by up to half.