ANTIOXIDATIVE CAFFEOYLQUINIC ACID-DERIVATIVES IN THE ROOTS OF BURDOCK (ARCTIUM-LAPPA L)

Five antioxidative caffeoylquinic acid derivatives were isolated from the roots of burdock (Arctium lappa L.), an edible plant in Japan. Their structures were established as 1-O-,5-O-dicaffeoylquinic acid (1), 1-O-,5-O-dicaffeoyl-3-O-succinylquinic acid (2), 1-O-,5-O-dicaffeoyl-4-O-succinylquinic acid (3), 1-O-,5-O-dicaffeoyl-3-O-,4-O-disuccinylquinic acid (4), and 1-O-,3-O-,5-O-tricaffeoyl-4-O-succinylquinic acid (5) on the basis of chemical and spectral (NMR, MS) evidence. The antioxidant activities were measured in a hexane/2-propanol solution of methyl linoleate in the presence of a radical initiator. The antioxidant efficiency increased in the order of alpha-tocopherol < chlorogenic acid < caffeic acid < (1) = (2) = (3) = (4) < (5).