Glycosides are a major group of plant secondary compounds characterized by one or more sugars conjugated to a lipophilic, possibly toxic aglycone, which is released upon hydrolysis. We compared small intestinal homogenate hydrolysis activity of three rodent and two avian species against four substrates: amygdalin and sinigrin, two plant derived glucosides, the sugar lactose, whose hydrolysis models some activity against flavonoid and isoflavonoid glucosides, and the disaccharide sugar maltose (from starch), used as a comparator. Three new findings extend our understanding of physiological processing of plant glucosides: (1) the capacity of passerine birds to hydrolyze plant glucosides seems relatively low, compared to rodents; (2) in this first test of vertebrates' enzymic capacity to hydrolyze glucosinolates, sinigrin hydrolytic capacity seems low; (3) in laboratory mice hydrolytic activity against lactose resides on the enterocytes' apical membrane facing the intestinal lumen, but activity against amygdalin seems to reside inside enterocytes.

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