Flavonoids from two Turkish <i>Centaurea</i> species and their chemotaxonomic implications

Abstract

Centaurea<em> asutro-anatolica </em>Hub.-Mor. and <em>C. kizildaghensis </em>Uzunh., E. Doğan & H. Duman, two indigenous perennial herbs from the Turkish flora, belong to the medicinally important genus <em>Centaurea </em>L. (fam: Asteraceae), which comprises <em>ca</em>. 600 species worldwide. While various <em>Centaurea </em>species are well-known for producing alkaloids, flavonoids, lignans and terpenoids, there is no report on any thorough phytochemical work on any of these two species available to date. In continuation of our phytochemical and bioactivity studies on the Turkish <em>Centaurea </em>species, four flavonoids apigenin (<strong>1</strong>), apigenin 7,4'-dimethyl ether (<strong>2</strong>), genkwanin (<strong>3</strong>) and quercetin (<strong>4</strong>) were isolated from the methanol extracts of the aerial parts of <em>C. austro-anatolica </em>and <em>C. kizildaghensis</em>, for the very first time. The structures of the flavonoids were elucidated conclusively by spectroscopic means, <em>i.e.</em>, UV, MS and 1D and 2D NMR data analyses. The distribution of these flavonoids (<strong>1</strong>-<strong>4</strong>) within the genus <em>Centaurea </em>and their possible chemotaxonomic implications within the genus <em>Centaurea </em>or the family Asteraceae have been discussed.