Two Novel Dicarboxylic Acid Derivatives and a New Dimeric Hydrolyzable Tannin from Walnuts

Abstract

In addition to the 16 previously reported polyphenols including 3 new ellagitannins, 2 novel dicarboxylic acid derivatives, glansreginins A ( 1 ) and B ( 2 ), and a new dimeric hydrolyzable tannin, glansrin D ( 3 ), were isolated, together with 15 known compounds from walnuts, the seeds of Juglans regia . The structures of the new compounds were elucidated on the basis of 1D- and 2D-NMR analyses and chemical data. The antioxidant effect of these isolates was also evaluated by SOD-like and DPPH radical scavenging activities. Keywords: Walnuts; Juglans regia; Juglandaceae; glansreginin A; glansreginin B; glansrin D; 2-hydroxycinchoninic acid; antioxidant activity; SOD-like effect; radical scavenger