New caffeic acid derivative from Tithonia diversifolia (Hemsl.) A. Gray butanolic extract and its antioxidant activity.

Tithonia diversifolia, Asteraceae, a promising alternative for insect control such as leaf-cutting ants, have revealed repellent and insecticidal activity against Atta cephalotes. The different biological activities of T. diversifolia, are due to the existence of sesquiterpene lactones and phenolic compounds. Some phenolic compounds have antioxidant activity and curiously also exhibited tyrosinase inhibitory activity, key enzyme in insect metamorphosis. To expand the plant phytochemical knowledge, especially for isolation and identification of secondary metabolites such as phenolic compounds not yet discovered in the polar extracts, a new caffeic acid derivative was isolated from the leaves of Tithonia diversifolia. The structure was determined as (E)-3-(((3-(3,4-dihydroxyphenyl)acryloyl)oxy)methyl)-2-methyloxyrane-2-carboxylic acid (1). Additionally, three known phenolic acids, 4,5-dicaffeoylquinic acid (2), 3,4-dicaffeoylquinic acid (3) and 3,5-dicaffeoylquinic acid (4), were also isolated; 1, 2 and 3 are the first reports for this species. The structures of compounds 1, 2 and 3 were established based on LC-MS and one- and two-dimensional (1D)- and (2D)-NMR spectroscopic analyses. Spectroscopic data of compound 1 were compared with 4-O-caffeoyl-2-C-methyl-d-threonic acid (5). Antioxidant activity evaluation in 96-well plate format, showed caffeic acid derivatives as strong 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavengers and moderate ferric reducing antioxidant power (FRAP).