Derivatives of resveratrol -- found in red wine grapes -- may impede cancer cell development, U.S. researchers said. The National Cancer Institute has teamed with a biotech firm to examine the potential benefit of resveratrol among cancer patients. Dr. Bryan C. Donohue of the University of Pittsburgh Medical Center, Shadyside Hospital, says early-stage clinical trials now under way are examining resveratrol's effectiveness among patients with heart disease, cancer, dementia and a host of other modern illnesses. In the meanwhile, some people simply looking for greater energy, enhanced clarity of thought and advanced overall well being are already benefiting from resveratrol supplementation, Donohue said. "I have had occasion to introduce hundreds of patients to daily resveratrol supplementation, ranging from healthy adults interested in health maintenance and prevention to more elderly individuals with specific health concerns," Donohue said in a statement. "People have experienced greater energy, increased exercise tolerance, crispness and clarity of thought and a general bounce in their overall level of well-being."