What is the best (cheapest/most potent/ highest quality) resveratrol on the market today

i'm looking for the best buy on resveratrol. there are so many brands on the market but they are too hard to compare. i'm taking Longevinex brand now but it's a bit too pricey. are there any better/cheaper quality brands available? thanks.

Resveratrol is found in grapevines (Vitis vinifera L). It occurs in the vines, roots, seeds and stalks, but its highest concentration is in grape skins. Wine also contains resveratrol. The concentration of resveratrol in red wine is much higher than that of white wine. The main difference between red and white wine production, besides the grapes used, is that for red wine the skins and seeds are involved in the process, while white wine is mainly prepared from the juice, essentially avoiding the use of grape skins and seeds. During the wine making process, resveratrol, as well as other polyphenols, including quercetin, catechins, gallocatechins, procyanidins and prodelphidins (condensed tannins), are extracted from the grape skins via a process called maceration.

Resveratrol, as well as the other polyphenols in wine, is thought to account in large part for the so-called French Paradox. The French Paradox鈥攖he finding that the rate of coronary heart disease mortality in France is lower than observed in other industrialized countries with a similar risk factor profile鈥攈as been attributed to frequent consumption of red wine.

In addition to grapes and wine, dietary sources of resveratrol include peanuts and mulberries. Resveratrol is also found in significant amounts in the dried roots and stems of the plant Polygonium cuspidatum Sieb. Et Zucc., also known as the Japanese knotweed. The dried root and stem of this plant is used in traditional Chinese and Japanese medicine as a circulatory tonic, among other things. This traditional Chinese and Japanese remedy is also known as Hu Zhang, Hu Chang, tiger cane, kojo-kon and hadori-kon. Most of the resveratrol-containing supplements which are marketed in the U.S. contain extracts of the root of Polygonium cuspidatum. Darakchasava, an ayurvedic herbal remedy, has as its principal ingredient Vitis vinifera L, and therefore, contains resveratrol. It is mainly used in ayurvedic medicine as a cardiotonic.