Flavonols isorhamnetin from

An examination of the flavonoids of Villarsia (Bohm et al., 1986) revealed a heterogeneous array of flavonol glycosides, based upon kaempferol, quercetin, and isorhamnetin, with each species exhibiting a unique assortment. Surprisingly, there were greater similarities between the pigment profile of V capensis and species from eastern Australia, V exaltata (Soland. ex Sims) G. Don from Tasmania and V. reniformis R. Br. from New South Wales, than with species native to... 

A detailed study of the flavonoid chemistry of the island endemics, the closely related G. tinctoria, and live additional species from the mainland provided additional evidence pointing toward G. tinctoria as the ancestral species (Pacheco et al., 1993). The flavonoid profiles of all species consisted of flavonol glycosides as major components with an unidentified flavone glycoside and several unidentified phenolic compounds (presumably not flavonoids). The pattern of distribution of the flavonol glycosides and unidentified flavones within the set of nine species proved to be extremely informative. (The phenols were ubiquitous and are not considered further.) Kaempferol glycosides were seen in neither the island species nor G. tinctoria, but were present, in several combinations, in the rest of the mainland taxa. The isorhamnetin glycosides showed the reverse pattern, with one exception the island endemics and G. tinctoria exhibited these compounds, whereas four of the other mainland species did not. The sole exception is G. boliviari, which exhibited one of the isorhamnetin derivatives. 

A series of flavonol glycosides esterified on the glucose residue linked at C-3 of the aglycone have been isolated from Quercus cerris L. (87-89) and Quercus saber L. (90-94) (49) (Fig. 10) Compounds 87 and 89 have isorhamnetin as the aglycone, while compounds 88 and 90-94 have kaempferol as the aglycone. Position 6" of the glucose residue is esterified by gallic acid unit in 87, and trans-p-coumaroyl acid in 88, 89 and 91-94. 

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