What is "xylostein"

Xylostein \Xy*los"te*in\, n. [Xylo- + Gr. ? bone.] (Chem.) A glucoside found in the poisonous berries of a species of honeysuckle ( Lonicera xylosteum), and extracted as a bitter, white, crystalline substance.

n. A bitter principle obtained from the berry of the fly honeysuckle (''Lonicera xylosteum'') and formerly used in medicine.