Four new caffeic acid metabolites, yunnaneic acids E-H, from Salvia yunnanensis

Four new caffeic acid metabolites, named yunnaneic acids E-H were isolated from the root of Salvia yunnanensis. Their structures have been established on the basis of spectroscopic and chemical evidence, Yunnaneic acids E and F are biogenetically derived from yunnaneic acid C, which is a Diels-Alder adduct of rosmarinic acid and caffeic acid, On the other hand, yunnaneic acids G and H are arylnaphthalene-type lignan esters derived by oxidative coupling between two molecules of rosmarinic acid, The existence of these compounds indicates that caffeic acid metabolism in S. yunnanensis is more complex than that in S. miltiorrhiza.