Chemical defense in birch. Platyphylloside: a phenol from Betula pendula inhibiting digestibility

Extracts of Scandinavian birch (Betula pendula Roth) buds and internodes of varying twig diameters have been investigated for their inhibitory effect of ruminant digestibility in vitro. The predominant inhibitory effect was observed in extracts containing the phenol platyphylloside, 5-hydroxy-1,7-bis-(4-hydroxy-phenyl)-3-heptan-one-3-O- beta -D-glucopyranoside. An important phenol of buds, apigenin-4',7-dimethylether, did not have any measurable effect on digestibility, while a nonphenolic fraction of bud extract had a slight inhibitory effect on digestibility. Implications for browsers feeding on birch are briefly discussed.