Bioavailability of the flavanone naringenin and its glycosides in rats

Naringenin, the predominant flavanone in grapefruit, mainly occurs as glyco sides such as naringenin-7-rhamnoglucoside or naringenin-7-glucoside. This study compared kinetics of absorption of naringenin and its glycosides in r ats either after a single flavanone-containing meal or after adaptation to a diet for 14 days. Regardless of the diet, circulating metabolites were gl ucurono- and sulfoconjugated derivatives of naringenin. The kinetics of abs orption of naringenin and naringenin-7-glucoside were similar, whereas nari ngenin-7-rhamnoglucoside exhibited a delay in its intestinal absorption, re sulting in decreased bioavailability. After naringenin-7-glucoside feeding, no glucoside was found in the cecum. However, after feeding naringenin-7-r hamnoglucoside, some naringenin-7-rhamnoglucoside accumulated in cecum befo re being hydrolyzed by intestinal microflora. Adaptation to flavanone diets did not induce accumulation of plasma naringenin. Moreover, flavanone ceca l content markedly decreased after adaptation, and almost no naringenin-7-r hamnoglucoside was recovered after naringenin-7-rhamnoglucoside feeding, su ggesting that an adaptation of cecal microflora had occurred. Overall, thes e data indicate that flavanones are efficiently absorbed after feeding to r ats and that their bioavailability is related to their glycosidic moiety.