Stability of black raspberry anthocyanins in the digestive tract lumen and transport efficiency into gastric and small intestinal tissues in the rat.

The fate of black raspberry anthocyanins in the gastrointestinal tract (GI) was evaluated. Fasted male rats (n = 30) were administered either 27 +/- 6.7 nmol of cyanidin 3-glucoside equivalent of anthocyanins and euthanized at 30, 60, 120, and 180 min or vehicle only and killed at 30 min (control) to collect bladder urine, GI contents, stomach, and small intestine. HPLC-MS analysis showed that anthocyanins in the gastric lumen decreased linearly over time (t(1/2) = 120 min). Anthocyanins in small intestinal tissue and lumen peaked at 120 min. Uptake by small intestinal tissue reached 7.5% of the administered dose, much higher than the reported bioavailability of these pigments. Ingested anthocyanin glycosides remain relatively stable in the GI contents (75-79% of administered dose). Selective decrease of cyanidin 3-glucoside in the small intestinal content likely resulted from beta-glucosidase activity. Urinary anthocyanin profiles reflected profiles present in the GI at the time of absorption.