Flavonoid Aglycones from the Bud Exudates of Three Betulaceae

The presence of flavonoid aglycones in bud ex­ cretions has been stressed and they have been stud­ ied in great detail by one of us in the 1970s. Exu­ date flavonoids were reported for members of the genera Aesculus (Hippocastanaceae, [1]), for Alnus, Betula, and Ostrya (Betulaceae, see [2]), for Populus (Salicaceae; see e.g. [3] and ref. therein), for Prunus (Rosaceae, [4]), and for Rhamnus (Rhamnaceae, [4]). Some more recent results were reported and concerned rare flavonoid aglycones in Betula nigra [5], phenolic triglycerides in Popu­ lus lasiocarpa [6], cinnamic acid derivatives in Populus nigra [7], and a stilbene in Alnus viridis [8], In the course of these studies, several minor prod­ ucts remained unidentified, due to paucity of ma­ terial and/or lack of markers. After isolation by preparative TLC, some of these have been identi­ fied by direct comparisons with authentic samples; one structure was elucidated by NM R analysis.