A comparison of the absorption and metabolism of the major quercetin in brassica, quercetin-3-O-sophoroside, to that of quercetin aglycone, in rats

Authors: WANG, YANLING - University Of Illinois; Berhow, Mark; BLACK, MOLLY - University Of Illinois; JEFFERY, ELIZABETH - University Of Illinois

Submitted to: Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/7/2019
Publication Date: 11/9/2019
Citation: Wang, Y., Berhow, M.A., Black, M., Jeffery, E.H. 2019. A comparison of the absorption and metabolism of the major quercetin in brassica, quercetin-3-O-sophoroside, to that of quercetin aglycone, in rats. Food Chemistry. 311:125880. https://doi.org/10.1016/j.foodchem.2019.125880.
DOI: https://doi.org/10.1016/j.foodchem.2019.125880

Interpretive Summary: Broccoli has a number of interesting constituents that may have an effect on the prevention of the development of chronic diseases in mammals. However, the exact mechanism of how they are absorbed by the gut from food and in what form they are absorbed has been difficult to ascertain. Broccoli contains phenolic compounds known as flavonoids, among other compounds, that are present chemically linked to sugar saccharides. It has not been characterized whether the flavonoid-sugars is absorbed intact, or whether the sugars are removed in the gut before the flavonoid is absorbed. Using a rat gut model and the purified flavonoid-sugar compound, this study shows that the flavonoid-sugar complex is both absorbed intact, and also absorbed after the original compound is broken down into the non-sugar form. Furthermore, the rat system will modify the absorbed compounds into slightly chemical modified forms as the process of metabolizing these compounds begins. This shows that there are many intact and altered forms of these flavonoid-sugar, which is a key piece of knowledge to lead to the assessment of the actual biological activity of these compounds in mammals that digest foods such as broccoli.

Technical Abstract: Broccoli has a number of bioactive phytochemicals including the flavonoid quercetin sophoroside, whose absorption by the body has not been carefully examined. Quercetin sophoroside was purified from Apocynum venetum (sword-leaf dogbane or Luo Bu Ma) and characterized by MS^2^, ^1^H and ^13^C NMR. An in situ rat gut model was used to compare absorption and metabolism of quercetin sophoroside with that of the well-studied quercetin aglycone. In agreement with the literature, the aglycone was absorbed in the jejunum, where it underwent glucuronidation, sulfation and methylation. In contrast and unexpectedly, the sophoroside was not deglycosylated to the aglycone, but was absorbed intact and partly underwent methylation and sulfation in the jejunum. Whereas the aglycone also underwent a little phase II metabolism and absorption in the cecum, only products of catabolism were seen for quercetin sophoroside following cecal introduction. Cecal catabolism by the microbiota was similar among the two substrates, forming derivatives of benzoic acid, phenylacetic acid, and phenyl propionic acid. Although sophorosides are common glycosides in brassica vegetables, red raspberries and other plants, this is the first study of sophoroside absorption and metabolism. It will be interesting to determine if the sophoroside has bioactivity.