Extraction of natural complex phenols and tannins from grape seeds by using supercritical mixtures of carbon dioxide and alcohol

Proanthocyanidins are supposed to have some therapeutical properties as ant ioxidants and antineoplasics. Most of the proanthocyanidins, however, are n ot commercialized since their separation from natural sources is either ver y expensive or not well-known. In this work, the feasibility of application of mixtures of carbon dioxide and alcohol under supercritical conditions f or selective extraction of some phenolic compounds from grape seeds has bee n studied, among them some low polymerized proanthocyanidins, their main mo nomer units, (+)-catechin and (-)-epicatechin, and some low molecular weigh t phenolic compounds, like gallic acid. An analytical-scale supercritical f luid extractor, whose operation was previously optimized, was used to carry out; the experiments. A commercial concentrate of complex phenols and tann ins from grape seeds was subjected to supercritical extraction in order to find the best operation conditions before directly extracting defatted mill ed grape seeds. The solvent capacity was found to increase with pressure an d with the amount of alcohol used as cosolvent as expected. Such variation in solvent capacity could be used for design of a selective separation proc ess where individual phenolic compounds or groups of them could be obtained . HPLC coupled with two types of detectors, diode array and mass spectromet ry, was used for tentative identification and quantification of complex phe nols and tannins in the extracts and in the raw materials used for extracti on.