Dietary Supplement. Support for the Aging Brain* Science-Based Nutrition™. Advancing the Frontiers of Brain Health Enhancement*. Flavonol Antioxidant Support for Healthy Aging* Best Fisetin featuring Cognisetin™ offers a naturally sourced flavonol that displays many effects on brain cells and cognitive function pathways in preclinical research. Fisetin is a bioflavonoid antioxidant that can help maintain glutathione levels and mitochondrial function in the presence of oxidative stress. It has potential to cross the blood brain barrier, which may help maintain neuronal function even in the face of factors that contribute to the normal age-associated decline in.