Concentrations of Blood Serum and Urinal Ellagitannin Metabolites Depend Largely on the Post-Intake Time and Duration of Strawberry Phenolics Ingestion in Rats

The different duration of a strawberry phenolic fraction intake and different post-intake time were experimental factors affecting the concentrations of ellagitannin metabolites in the urine and blood serum of rats. For four days, the animals were gavaged once a day as follows: group C (water, days 1-4), group F1-4 (fraction, days 1-4), group F1-3 (fraction, days 1-3; water, day 4), group F1-2 (fraction, days 1, 2; water, days 3, 4), group F3-4 (water, days 1, 2; fraction, days 3, 4), and group F4 (water, days 1-3; and fraction, day 4). The daily dosage of the fraction gavaged to one rat was 20 mg/kg of body weight. The fraction contained monomers and dimers of ellagitannins as well as proanthocyanidins. The caecal, urinal, and blood serum ellagitannin metabolites were analysed 12 h after the last treatment. Ellagic acid, urolithin A, and nasutin A were detected in the caecal digesta. In turn, urolithin A, nasutin A, and their glucuronide conjugates were detected in the urine, while urolithin A glucuronide, nasutin A glucuronide, and ellagic acid dimethyl ether glucuronide were found in the serum. The highest caecal and urinal concentrations of ellagitannin metabolites followed the F1-4 treatment. In the serum, the highest concentrations of the metabolites were determined in the rats administered the phenolic fraction during days 1-4 and 3-4. No metabolites were found in the rats following the C and F1-2 treatments. The results suggest that the presence of ellagitannin metabolites in the rat’s urine and serum largely reflects the concentrations of caecal metabolites and the number of subsequent days of strawberry phenolic fraction administration.