A method for enhancing at least one of alertness, attention, concentration and memory in a person in need thereof, comprising administering a composition to said person, said composition comprising: a) an effective amount of an extract of Cyperus esculentus peel, Cyperus esculentus rhizomes, or a combination thereof; b) an effective amount of mangiferin, norathyriol, or an extract comprising mangiferin or norathyriol; or c) a synergistic combination of (a) and (b).