Antioxidant properties of aqueous extracts from Terminalia catappa leaves

Aqueous extracts were prepared from green, yellow fallen and red fallen leaves of Terminalia catappa L. (Combretaceae) and their antioxidant activity, scavenging and chelating abilities were evaluated. Aqueous extracts from three different leaves showed high antioxidant activities and moderate scavenging abilities on hydroxyl radicals at 1 mg/ml. EC₅₀ values in antioxidant activity were 0.549-0.557 mg/ml whereas those in scavenging ability on hydroxyl radicals were 0.631-0.686 mg/ml for aqueous extracts prepared from three leaves with boiling water for 3 min. EC50 values in reducing power were 0.15-0.23 mg/ml. EC50 values in scavenging abilities on superoxide anion and 1,1-diphenyl-2-picrylhydryl radicals were 0.36-0.44 and 10.4-35.3 mg/ml, respectively. EC50 values in chelating abilities on ferrous and cupric ions were 0.41-2.50 and 8.96-9.89 mg/ml, respectively. Based on the results obtained, the aqueous extracts displayed higher antioxidant properties. Six phenolic compounds identified in the aqueous were p-hydroxybenzoic acid, 4-hydroxyphenylpropionic acid, m-coumaric acid, 3,4-dihydroxybenzoic acid, p-coumaric acid and gallic acid. Therefore, the aqueous extracts from three different leaves of T. catappa might be a potential antioxidant supplement for application in food products or as a drink.