Alnus glutinosa and A. incana (Betulaceae), are a small to medium size tree, native to the Northern Hemisphere. The leaves of this species are used in the Republic of Belarus as a source of antioxidants. The aim of this work was investigation of antioxidant activities and total phenolics content in various extracts obtained using water, mixture water with ethanol (from 9:1 to 2:8), and ethanol from A. glutinosa and A. incana leaves. Phenolics content was determined by method with Folin-Ciocalteu reagent and calculated on ellagic acid. The antioxidant activities were measured utilising 1,1-diphenyl-2 picrylhydrazyl (DPPH) radical scavenging test. The highest phenolics concentration was observed in the extracts prepared by extraction with the mixture of water:ethanol from 7:3 to 3:7 and ranged from 17.82% to 18.96% for A. glutinosa and from 10.82% to 12.55% for A. incana. This extracts exhibited the highest free radical scavenging activity ranging from 49.21% to 49.42% and from 41.28% to 41.67% for A. glutinosa and A. incana respectively, comparable to the activity of quercetin. Therefore the mixture of water:ethanol from 7:3 to 3:7 should be used for preparing extracts from this species for medicinal purposes. Results also indicated the existence of a high correlation between antioxidant activity and total phenolics content.

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