Resveratrol (3,5,4′-trihydroxy-trans-stilbene) is a stilbenoid, a type of natural phenol, and a phytoalexin produced by several plants in response to injury or, when the plant is under attack by pathogens such as bacteria or fungi. Sources of resveratrol in food include the skin of grapes, blueberries, raspberries, mulberries.
polygonum cuspidatum is used as raw material, extracted, extracted resveratrol crude, and then purified. Crude extraction technologies include organic solvent extraction method, the new method of alkaline extraction and enzymatic extraction method. New methods like microwave-assisted extraction, CO2 supercritical extraction and ultrasonic extraction are also applied. The main purpose of purification is to extract cis-resveratrol and trans-resveratrol and polydatin from raw resveratrol to obtain trans-resveratrol. Common methods of purification are chromatography, silica gel column chromatography, thin-layer chromatography, high performance liquid chromatography and the like.
Because of the low concentration of resveratrol in the plant and the high extraction cost, using chemical, biological, genetic engineering and other methods to obtain resveratrol has become an indispensable means for its development process. The roadmap to synthesis resveratrol is as follows:
3,5-dihydroxybenzoic acid (3) forms 3,5-dihydroxybenzoic acid methyl ester (4) by esterification reaction. Choose methyl ether as phenolic hydroxyl-protecting groups. (4) reacts with dimethyl sulfate to get 3,5-di-methoxybenzoate (5). (5) generates the corresponding benzene methanol (6) after reduction, and forms 3, 5-dimethoxy benzyl bromide (7) through further bromination. Then diethyl (3,5-dimethoxy benzyl) phosphonate (8) can be get by roman abramovich's reaction. (8) reacts with p-anisaldehyde to form the key intermediate 3,4,5-trimethoxy-trans-stilbene (9) via Wittig-Honer reaction. Finally, methyl can be removed by freshly prepared aluminum triiodide. Then the aimed product resveratrol can be separated by thin layer chromatography.
Resveratrol is found in grapes, wine, grape juice, peanuts, cocoa, and berries of Vaccinium species, including blueberries, bilberries, and cranberries .
In grapes, resveratrol is found only in the skins. The amount of resveratrol in grape skins 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 also an important determinant of its resveratrol content. Because grape skins are removed early during the production process of white and rosé wines, these wines generally contain less resveratrol than red wines . Therefore, because of variations between types of wine, vintages, and regions, it is very difficult to provide accurate estimates of resveratrol content in the thousands of wines from worldwide wineries. Yet, it appears that resveratrol content in wine is usually low, highly variable and unpredictable, and resveratrol is only a minor compound in the complete set of grape and wine polyphenols .