The profile of buckwheat tannins based on widely targeted metabolome analysis and pharmacokinetic study of ellagitannin metabolite urolithin A

Buckwheat was known as enrichment of flavonoids and phenolic acids, but the tannins profile in buckwheat seeds was still unclear. Particularly, the permeability mechanism of ellagitannin metabolite urolithin A (UA) getting through blood brain barrier (BBB) and its variation in brain tissue was also unclear. Widely targeted metabolome analysis and tannins quantification were performed to evaluate the tannins profile in Tartary and common buckwheat seeds. A pharmacokinetic study of UA was carried out to evaluate the permeability and variation in brain. A Total of 543 substances were detected in Tartary buckwheat and 533 substances in common buckwheat. Four hydrolysable and six condensed tannins and gallic acid constituted all of the 11 tannins, while the ellagitannins and ellagic acid were not detected in buckwheat seeds. Gallic acid and procyanidin C1 were abundant, the gallic acid in Tartary and common buckwheat was 5.58 and 16.26 mg/kg, respectively, and procyanidin C1 was 6.18 and 3.17 mg/kg. Totally, 30 different molecules were identified between the species. UA could go through digestive system and cross BBB to enter cortex and hippocampus. This study provided deep insights into the composition of buckwheat seeds, which will irritate the application of buckwheat and UA.