Characterization of phenolic constituents in hazelnut kernels

Abstract Hazelnuts contain biologically active phenolic compounds and are widely used for their nutritional value. In this study, the phenolic compounds contained in hazelnuts were isolated from the kernels of Corylus avellana L. and investigated. Spectral analyses revealed two new acetophenone glycosides, characterized as 2′,4′,6′-trihydroxyacetophenone 4′-O-(2-O-β-D-apiosyl)-β-D-glucoside and 2′,4′,6′-trihydroxyacetophenone 4′-O-(2-O-β-D-apiosyl-6-O-α-L-arabinosyl)-β-D-glucoside, and four known compounds. Four high-molecular mass condensed tannin fractions were detected in the water-soluble fraction of the extract, characterized as B-type procyanidin consisting of extension and terminal units. Gel permeation chromatography analyses revealed that the average molecular mass, based on the polystyrene standard, was approximately 15 000–113 000. These high-molecular mass condensed tannin fractions were chemically characterized and exhibited different molecular weights. The fractions of high-molecular mass condensed tannins were obtained from hazelnuts and tested for 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity. The EC50 values indicated significant activity for all the fractions.