Resveratrol is extracted from "Knotweed", the rhizome of Polygonum cuspidatum. Mainly produced in Jiangsu, Zhejiang, Anhui, Guangdong, Guangxi, Yunnan, Sichuan, Guizhou and other places. The roots are dug out in spring and autumn, the fibrous roots are removed, washed and dried in the sun. Polygonum cuspidatum roots and rhizomes contain free anthraquinones and anthraquinone glycosides, mainly emodin, emodin methyl ether, chrysophanol, anthraglycoside A, anthraglycoside B, etc. It also contains resveratrol, resveratrol glycosides, protocatechuic acid, d-catechin, cassia anthrone-8-glucoside, β-sitosterol glucoside and glucose, rhamnose, ginger sugar, Amino acids, tannins and copper, iron, manganese, zinc, potassium and potassium salts, etc.
Natural plant extraction method: take Polygonum cuspidatum as raw material, extract and separate the crude Res from it, and then purify it. Crude extraction techniques mainly include organic solvent extraction, alkali extraction and enzyme extraction, and new methods such as microwave-assisted extraction, CO2 supercritical extraction, and ultrasonic-assisted extraction are also used. The purpose of purification is mainly to separate the cis and trans isomers and resveratrol glycosides of resveratrol in the extracted Res crude product to obtain trans-resveratrol. Commonly used purification methods include chromatography, silica gel column chromatography, thin-layer chromatography, and high-performance liquid chromatography.