Phenolic compounds from Canna edulis Ker residue and their antioxidant activity

Using the bleaching of the free radical scavenger 1,1-diphenyl-2-picrylhydrazyl (DPPH) as the guiding assay, a novel compound, 4-(3-(3,4-dihydroxyphenyl)acryloyl)-6-hydroxy-1-methoxy-1,2,3,4-tetrahydronaphthalene-2-carboxylic acid, was isolated from water-soluble extract of Canna edulis Ker with ten known compounds: rosmarinic acid, salvianolic acid B, ferulic acid, caffeic acid, 1-caffeoylquinic acid, 3-caffeoylquinic acid, 4-caffeoylquinic acid, 5-caffeoylquinic acid, salicylic acid and gallic acid. The structures were characterized by spectroscopic methods including extensive 2D-NMR techniques. Moreover, antioxidant activities of total extract and the new compound were determined through six different kinds of modes. In view of antioxidant activity confirmed, C. edulis extract and the new compound can be developed as natural food additives. In addition, the correlations between concentration and antioxidant activity and among the modes were analyzed. The results of DPPH and ABTS radical scavenging and FRAP assay exhibited high consistency. However, those for other modes showed difference to a certain extent.

► A new compound, 4-(3-(3,4-dihydroxyphenyl)acryloyl)-6-hydroxy-1-methoxy-1,2,3,4-tetra-hydronaphthalene-2-carboxylic acid, was isolated from water-soluble extract of Canna edulis Ker residue. ► The new compound exhibits high antioxidant activity. ► C. edulis extract and the new compound can be developed as natural food additives.