New bisabolane-type sesquiterpenes from the aerial parts of Lippia dulcis

Two new bisabolane-type sesquiterpenes, lippidulcine A (3) and epilippidulcine A (4), have been isolated from the aerial parts of Lippia dulcis TREV. along with five known flavonoids, eirsimaritin (5), salvigenin (6), eupatorin (7), 5-hydroxy-6,7,3',4'-tetramethoxyflavone (8) and 5,3'-dihydroxy-6,7,4',5'-tetramethoxyflavone (9), three known phenylethanoid glycosides, decaffeoylverbascoside (10), acteoside (11) and isoacteoside (12), and two known iridoid glucosides, 8-epiloganin (13) and lamiide (14). Their chemical structures have been determined on the basis of spectroscopic data. Among them, 5, 7, and 9 exhibited almost the same activity as that of a-tocopherol, and 10-12 were identified as stronger antioxidants than a-tocopherol using the ferric thiocyanate method.