The in vivo bioavailability of the flavone-C-glycosides has been little studied compared to their O30 glycoside analogues, which are both more common in nature and considered more easily 31 hydrolyzed than C-glycosides, by both enterocytes and gut microbiota. In this study, we used 32 vitexin-2-O-xyloside (VOX), an apigenin-8-C-glucoside-2-O-xyloside, purified from seeds of Swiss 33 chard (Beta vulgaris cicla), to investigate VOX absorption into portal blood compared to its 34 aglycone, apigenin. We used a rat model in which we ligated the ileo- and colo-caecal junctions, 35 then administered apigenin or VOX directly into the caecum. Blood samples were drawn from the 36 portal vein at timed intervals over 40 min. The kinetic profile of appearance in portal blood of the 37 compounds and their metabolites was evaluated by HPLC-ESI-MS. Apigenin was found in portal 38 blood both as the aglycone and as an apigenin-glucuronide derivative. The VOX was found 39 unchanged and as a reduced monoglycoside, which underwent glucuronidation. By collecting the 40 bile, we confirmed that the liver received unchanged VOX, which was returned to the gut by 41 enterohepatic recirculation for reabsorption from the ileum. The amount of apigenin and VOX 42 remaining in the caecum accounted for ~15% and ~26%, respectively. These data show for the first 43 time that the C-glycoside VOX is absorbed unchanged and undergoes enterohepatic recirculation in 44 addition to hydrolysis to the monoglycoside, reduction and conjugation to form a bioavailable 45 glucuronide.

Caecal Absorption of Vitexin-2-O-xyloside and its Aglycone Apigenin, in the Rat

ANGELINO, DONATO;NINFALI, PAOLINO;
2013

Abstract

The in vivo bioavailability of the flavone-C-glycosides has been little studied compared to their O30 glycoside analogues, which are both more common in nature and considered more easily 31 hydrolyzed than C-glycosides, by both enterocytes and gut microbiota. In this study, we used 32 vitexin-2-O-xyloside (VOX), an apigenin-8-C-glucoside-2-O-xyloside, purified from seeds of Swiss 33 chard (Beta vulgaris cicla), to investigate VOX absorption into portal blood compared to its 34 aglycone, apigenin. We used a rat model in which we ligated the ileo- and colo-caecal junctions, 35 then administered apigenin or VOX directly into the caecum. Blood samples were drawn from the 36 portal vein at timed intervals over 40 min. The kinetic profile of appearance in portal blood of the 37 compounds and their metabolites was evaluated by HPLC-ESI-MS. Apigenin was found in portal 38 blood both as the aglycone and as an apigenin-glucuronide derivative. The VOX was found 39 unchanged and as a reduced monoglycoside, which underwent glucuronidation. By collecting the 40 bile, we confirmed that the liver received unchanged VOX, which was returned to the gut by 41 enterohepatic recirculation for reabsorption from the ileum. The amount of apigenin and VOX 42 remaining in the caecum accounted for ~15% and ~26%, respectively. These data show for the first 43 time that the C-glycoside VOX is absorbed unchanged and undergoes enterohepatic recirculation in 44 addition to hydrolysis to the monoglycoside, reduction and conjugation to form a bioavailable 45 glucuronide.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11576/2560974
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