What is a glucoside found in the poisonous berries of a species of honeysuckle (Lonicera xylosteum), and extracted as a bitter, white, crystalline substance called?

xylostein — A glucoside found in the poisonous berries of a species of honeysuckle (Lonicera xylosteum), and extracted as a bitter, white, crystalline substance. (Webster's 1913.)

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