HEARTWOOD FLAVONOIDS AND THE INFRAGENERIC RELATIONSHIPS OF RHUS (ANACARDIACEAE)

Abstract

Heartwood flavonoids of 23 taxa of Rhus L. were surveyed in order to assess infrageneric relationships and classification. Fourteen flavonoids and two coumarins were detected in the heartwood extracts. All taxa were characterized by a flavonoid complement consisting of eight 5‐deoxyflavonoids involving several aglycone classes (e.g., flavonols, flavones, aurones, chalcones and dihydroflavonols) and the aurone rengasin. None of the 5‐hydroxyl analogs of the 5‐deoxyflavonoids were detected in the heartwood extracts. Infraspecific flavonoid patterns were uniform in different populations, although the presence of 3′,4′‐dihydroxyflavone 4′‐O‐β‐glucoside varied in some taxa. Taxa of Rhus subgenus Rhus consistently differed from all taxa of Rhus subgenus Lobadium in lacking glycosides of fisetin, butein and 3′,4′‐dihydroxyflavone. The major evolutionary trend in the heartwood flavonoids of Rhus appears to be accumulation of simple mono‐ or diglucosides. Data from heartwood flavonoids suggest that Rhus be treated as consisting of two subgenera ( Rhus and Lobadium ) and that subgenus Lobadium be divided into three sections.