Identification and Biosynthesis of Glucosylated and Sulfated Flavonols in Flaveria bidentis

Abstract

1.The flavonoid constituents of Flaveria bidentis have been identified as the 3-O-glucosides of kaempferol. 6-methoxykaempferol and 6-methoxyquercetin (patuletin), as well as six flavonol sulfate esters belonging to quercetin and isorhamnetin. The two latter glucosides are reported here for the first time in this species; whereas quercetin-3,7-disulfate, is a novel compound from nature.2.The amounts of both glucosides and sulfate esters in young seedlings were highest in buds > stems > leaves on fresh weight basis, whereas they were undetectable in the root. There were striking quantitative differences in the flavonoid pattern of young seedlings, as compared with mature shoots, especially the flavonol sulfate esters which were predominant in seedlings.3.The biosynthesis of both groups of flavonoids from [3H]cinnamate and [35S]sulfate showed that the former was predominantly incorporated into glucosides whereas the latter, into sulfate esters; thus indicating that sulfation is a later step in the biosynthesis of flavonol sulfate esters.4.The significance of the glucosylation and sulfation reactions was discussed in relation to the regulation of biosynthesis and compartmentation of both groups of compounds.