Gastrointestinal uptake of nasunin, acylated anthocyanin in eggplant

We previously showed that nasunin, acylated anthocyanins in eggplant peel, comprises two isomers, cis-nasunin and trans-nasunin. In this study, gastrointestinal absorption of cis- and trans-nasunins was studied in rats. Orally administered nasunins were quickly absorbed in their original acylated forms and maximally appeared in blood plasma after 15 min. When the maximum plasma concentration and area under the plasma concentration curve were normalized by orally administered dose (micromoles per kilogram), there was no significant difference in the uptake efficiency between two isomers and both exhibited a plasma level almost identical to that of delphinidin 3-O-beta-D-glucopyranoside. However, metabolites such as 4'-O-methyl analogues and extended glucuronides which were observed for delphinidin 3-O-beta-D-glucopyranoside and cyanidin 3-O-beta-D-glucopyranoside metabolisms were not detected in urine or blood plasma. Moreover, deacylated and glycolytic products of nasunins such as delphinidin 3-O-beta-D-glucopyranoside or delphinidin (aglycone) were also not detected in blood plasma even after oral administration for 8 h. These results indicated that nasunins were absorbed in their original acylated forms and exhibit a bioavailability almost identical to that of nonacylated anthocyanins.