A Novel Type of Flavonoids: Flavonol Esters from Fern Exudates

Farinose exudates on fronds of Notholaena species are known to consist of flavonoid aglycones. These are predominantly methylated flavones and flavonols, sometimes chalcones and dihydrochalcones. Flavonols with unusual properties, excreted as major farina components by some species, have been found to be derivatives of methylated flavonols, esterified in position 8 with butyric or acetic acids, respectively. These are a novel type of flavonoids. They occur as twin-pairs, some with very great differences in proportions. Their presence in a group of species within the genus has chemotaxonomic implications. Two of the flavonols resulting from hydrolysis are new compounds.