The flavonoids of Mitella, Bensoniella, and Conimitella (Saxifragaceae)

Abstract

Flavonoid profiles have been determined for 16 species of Mitella and for the two monotypic genera, Bensoniella and Conimitella. With a single exception the profiles are based upon the flavonols kaempferol, quercetin, and myricetin. The flavanone eriodictyol was seen in two Japanese species of Mitella. The flavonols exist as a series of 7-O-mono-, 3-O-mono-, 3-O-di-, and 3-O-triglycosides, although not all levels of glycosylation occur in each taxon. 7-O-Methylkaempferol and 7-O-methylquercetin were found in M. nuda and M. diphylla; M. nuda also has isorhamnetin. The flavonoids of M. nuda are unique in the genus, but otherwise the distribution of the pigments does not offer support for Rydberg's view of the species being assigned to four genera or Rosendahl's view that Mitella comprises two sections. The flavonoid profile of Bensoniella oregona clearly distinguishes it from Mitella. Flavonoid data for Conimitella williamsii agree in general with those of a moderately advanced species of Heuchera in agreement with Savile's views on the origin of Conimitella. Our results are discussed in terms of the recent finding that Conimitella and Mitella form natural hybrids.