Antioxidants chemically bind with and neutralize free radicals, which are reactive oxygen and nitrogen molecules that can damage cells and tissue. Grape seed extracts have shown a broad range of pharmacological activities related to the antioxidant properties of the polyphenolic compounds that are present.
Now, researchers at Virginia Tech and the University of Cadiz in Spain have developed a method using carbon dioxide instead of organic solvents to extract many of the antioxidants from grape seeds. The new method produces an extract with greater potency without using toxic chemicals, takes 25 percent less time, and can be fully automated.
Larry Taylor, chemistry professor and department chair at Virginia Tech, will explain the work at the 220th national meeting of the American Chemical Society Aug. 20-24 in Washington, D.C.
When University of Cadiz analytical chemist Miguel Palma took a sabbatical at Virginia Tech to be trained in supercritical fluid technology last year, he naturally chose to work on enhancing one of his nation's important products, grapes.
The solvent process not only uses toxic materials but introduces oxygen. Many of these compounds are air and light sensitive meaning that if they are isolated under these conditions some of their antioxidant activity will be lost. Supercritical fluid extraction with carbon dioxide based fluids allows for the isolation of compounds without interference from air and light thereby guaranteeing conservation of their antioxidant properties.
"This 'green chemistry' is a natural for food and pharmacological processing," says Taylor.
But not only did Palma and Taylor develop a better way to process grape seeds, his development may lead to two new uses for the beneficial extract. He formed two additional collaborations, testing the grape seed extract for anitmicrobial activity and for the presence of glycosides, which contribute to wine flavor.
Palma's wife, Rosa M. Varela, an organic chemist at Cadiz, was on sabbatical with the Department of Pharmaceutical Sciences at Mercer University in Atlanta. She and colleagues there, Stephen J. Cutler and Horace G. Cutler, discovered a high degree of antimicrobial activity toward human pathogens from the CO2 extract, which they and Virginia Tech scientists reported in the Journal of Agricultural and Food Chemistry in November 1999 (Vol. 47, No. 12, pages 5044-5048). "This introduces a new use for specific grape seed extracts," Taylor explains.
Meanwhile, Palma was meeting with the wine processing experts in the Department of Food Science and Technology at Virginia Tech, among them Bruce Zoecklein, whose work with grape glycosides and wine flavor Palma had read. Palma and Zoecklein conducted a set of experiments to isolate glycosides using methanol-modified CO2 from grapes. The yield of glycosides with CO2 coincided with the amount isolated using conventional liquid extraction; plus, the supercritical fluid method took less time and can be fully automated. This work was also published in the Journal of Agricultural and Food Chemistry in February 2000 (Vol. 48, No. 3, pages 775-779).
The talk, titled "Extraction of Antioxidants from Grape Seeds Employing Pressurized Fluids" (AGFD 136), is by Taylor, Palma, and Mehdi Ashraf-Khorassani, Virginia Tech research scientist. It will be delivered at 9:35 a.m. on Thursday, Aug. 24, in Convention Center room 13-14. It is part of the Quality Management of Nutraceuticals Symposium.
PR Contact: Susan Trulove
540-231-5646 strulove@vt.edu
Journal
Journal of Agricultural and Food Chemistry