Influence of fatty acid patterns on the intestinal absorption pathway of quercetin in thoracic lymph duct-cannulated rats

Since it is known that dietary fats improve the bioavailability of the flavonol quercetin, we purposed to investigate whether this effect is due to increased lymphatic transport of quercetin. In rats with implanted catheters in the thoracic lymph duct, we administered quercetin into the duodenum with TAG emulsions containing either long-chain fatty acids (LCT) or medium-chain fatty acids (MCT). Controls received quercetin together with a glucose solution. LCT administration increased the lymphatic output of quercetin (19.1 (SEM 1.2) nmol/8 h) as well as the lymph-independent bioavailability of the flavonol, determined as area under the plasma concentration curve (1091 (SEM 142) mu M x min). Compared with glucose administration, MCT neither increased the lymphatic output (12.3 (SEM 1.5) nmol/8 h) nor the bioavailability of quercetin (772 (SEM 99) mu M x min) significantly (glucose group: 9.8 (SEM 1.5) nmol/8 h and 513 (SEM 55) mu M x min, respectively). Because LCT are released within chylomicrons into the intestinal lymph while MCT are mainly released into the portal blood, we conclude from the present results that dietary fats that are mainly composed of LCT improve quercetin bioavailability by increasing its transport via the lymph, thereby circumventing hepatic first-pass metabolism of the flavonol. In addition, LCT could enhance quercetin absorption by improving its solubility in the intestinal tract.