Determination of Proanthocynidins in Fresh Grapes

Abstract

Medical benefits derived from grape extracts and red wine have been recently documented. In these regards, fresh grapes were collected from six Italian table grape varieties grown at the Rutgers Fruit Research and Extension Center in Cream Ridge, N.J. These samples were analyzed for proanthocynidins (PACs) which are the nutraceutical compounds considered to be bioactive in grapes. Seeded red grapes, seedless red grapes, seeded purple grapes and seedless green table grapes were also purchased from a New Jersey supermarket and analyzed for PACs. An LC/ESI-MS analytical method under low CID level of 20% was used to quantitate the PACs. Separated proanthocynidins (PACs) were individually analyzed and determined by their molecular ion peaks under positive ion mode, and led to the identification of dozens of proanthocynidins (PAC). Using HPLC/ESI-MSD, the proanthocyanidin monomers, (+)-catechin (C), (-)-epicatechin (EC), (-)-catechin gallate (CG), and (-)-epicatechin gallate (ECG) in these fresh grape samples were quantified under MRM mode. These identified catechins are the same phytochemicals that exist in green tea which is renowned for these same healthful components. This research revealed that the total concentration of PAC monomers in the six fresh table grape samples from New Jersey grown grapes ranged from 0.009% to 0.04%, which is much higher than that found in the four fresh table grape samples purchased from supermarket that contained concentrations from trace level to 0.005%. While the New Jersey grown grapes could not be directly compared to the supermarket grapes, this study provides a base-line data of expected PAC levels from standard supermarket grapes, and shows that these Italian grape varieties grown in New Jersey were rich in PACs.