Abstract
New sesquiterpene lactones have been isolated from the chloroform-soluble fraction of Amberboa ramosa and assigned two structures 4beta-(chloromethyl)-3beta,4alpha-dihydroxy,8alpha-[(s)-2-carboxypropionoxy]-1alphaH,5alphaH,6betaH,7alphaH-guaia-10(14),11(13)-dien-6,12-olide (1) and 4beta-(chloromethyl)-3beta,4alpha-dihydroxy, 8alpha-[(s)-3-hydroxy-2-methylpropionyloxy]-1aH,5aH,6pH,7aH-guaia-10(14),11(13)-dien-6,12-olide (2), respectively. In addition 5-hydroxy-6-methyl-7-methoxyflavone (3), 6,2',5'-trihydroxy-3,5,7-trimethoxyflavone (4) and 5-hydroxy-3,7,8,2'-tetramethoxyflavone (5) have also been reported for the first time from this species. Compounds 1 and 2 displayed promising inhibitory potential against enzyme urease in a concentration-dependent fashion.