Four components of black currant anthocyanins (BCA), delphinidin 3-O-beta-rutinoside (D3R), cyanidin 3-O-beta-rutinoside (C3R), delphinidin 3-O-beta-glucoside (D3G), and cyanidin 3-O-beta-glucoside (C3G), were found to be directly absorbed and distributed to the blood and excreted into urine as the glycosylated forms. In a rat study, following oral administration of purified D3R, C3R, and C3G (800 micromol/kg of body weight), the anthocyanins were detected in the plasma and the C(max) values were 580 +/- 410, 850 +/- 120, and 840 +/- 190 nmol/L, respectively, 0.5-2.0 h after administration. In a human study, when a mixture of BCA [6.24 micromol (3.58 mg) consisting of 2.75 micromol (1.68 mg) of D3R, 2.08 micromol (1.24 mg) of C3R, 1.04 micromol (0.488 mg) of D3G, and 0.37 micromol (0.165 mg) of C3G/kg of body weight)] was orally ingested by eight volunteers, D3R, C3R, D3G, and C3G were detected in the plasma and urine. The plasma C(max) values were 73.4 +/- 35.0, 46.3 +/- 22.5, 22.7 +/- 12.4, and 5.0 +/- 3.7 nmol/L, respectively, 1.25-1.75 h after intake, and the cumulative excretion of the four compounds in urine in the period 0-8 h after intake was 0.11 +/- 0.05% of the dose ingested. These results indicate that 3-O-beta-rutinosyl anthocyanins were directly absorbed and distributed to the blood.

Anthocyanins have been suggested to improve visual functions. This study examined the effect of four anthocyanins in black currant fruits on the regeneration of rhodopsin using frog rod outer segment (ROS) membranes. Cyanidin 3-glycosides, glucoside and rutinoside, stimulated the regeneration, but the corresponding delphinidins showed no significant effect. The formation of a regeneration intermediate was suggested to be accelerated by cyanidin 3-rutinoside. Their effects on the cGMP-phosphodiesterase activity in the ROS membranes were also investigated but found to be negligible. It was concluded that the major effect of anthocyanins in rod photoreceptors is on the regeneration of rhodopsin.

The fructosyl transfer to sucrose was investigated, and Aspergillus niger ATCC2061 1 was selected as the most suitable strain for fructooligosaccharide production. This strain showed very high enzyme productivity, and its transfructosylating activity was very strong compared to its hydrolyzing activity. Fructooligosaccharides could be more effectively prepared with a higher concentration of sucrose if use could be madeof an enzymehaving higher transfructosylating ability. Treatment of 50% (w/v) sucrose with the A. niger enzyme afforded a mixture of fructooligosaccharides with inulin-type structures of lF(l-/?-fructofuranosyl)n-sucrose {n = \ to 3). The individual saccharides could be separated by the combination of a carbon column chromatography and preparative HPLC.

For better understanding of the physiological function of anthocyanins, the absorption and metabolism of cyanidin 3-O-beta-D-glucopyranoside (Cy3G), which is one of the major anthocyanins in colored food materials, were precisely investigated. Combining two modalities newly developed, that is, highly sensitive semi-micro-HPLC and vein cannulation, Cy3G and its four major metabolites (M1-M4) were detected in the blood plasma of rats after oral administration of Cy3G (100 mg/kg of body mass). The plasma concentration of Cy3G reached its maximum at 15 min after the ingestion. Metabolite 2 (M2) and metabolite 3 (M3) showed their maximum plasma levels at 15 and 30 min, respectively, whereas metabolite 1 (M1) and metabolite 4 (M4) showed their maximum levels at 60 and 120 min, respectively. The maximum plasma concentrations of the four metabolites were in the following order: M3 (21 nM) > M4 (20 nM) > M1 (8.5 nM) > M2 (5 nM). When Cy3G was directly injected into the neck vein, only M2 and M3 were detected in the plasma, indicating that both M1 and M4 were produced during absorption from the gastrointestinal tract. Tandem MS analysis of the metabolites showed that M2 and M3 were monomethylated Cy3G, while M1 and M4 were glucuronides of Cy and methylated Cy, respectively. M3 was assigned as peonidin 3-O-beta-D-glucopyranoside (Pn3G) from the comparison of the retention time of authentic Pn3G.

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Many reports have described the bioavailability of anthocyanins; however, most of these reports investigated only the amount of anthocyanins excreted in urine. In the present study, we calculated the pharmacokinetic bioavailability of anthocyanins in rats by measuring the plasma concentration of delphinidin-3-rutinoside that had been administered orally or intravenously. Delphinidin-3-rutinoside was primarily absorbed in the blood and excreted into urine as unmetabolized forms with a T(max) of 26.3 min and a C(max) of 0.285 +/- 0.071 micromol/L. We detected small amounts of the metabolite 4'-O-methyl-delphinidin-3-rutinoside in the plasma, but we detected neither anthocyanidin (aglycone) nor glucuro- or sulfoconjugates. For the 8 h period after intake, delphinidin-3-rutinoside and 4'-O-methyl-delphinidin-3-rutinoside were excreted to urine at 795 +/- 375 and 12.3 +/- 2.91 nmol, respectively. Relative to intravenous injection, oral administration of delphinidin-3-rutinoside resulted in complete bioavailability (0.49 +/- 0.06%). Analysis of delphinidin-3-rutinoside plasma concentrations in bile cannulated rats revealed that, for the 8-h period after intake, the intact delphinidin-3-rutinoside excretion ratio in bile was 11% of the excretion ratio of 4'-O-methyl-delphinidin-3-rutinoside, 1.91 +/- 0.35 nmol versus 17.4 +/- 8.67 nmol, respectively. Setting the bile duct cannulation in a Bollman-type cage, however, significantly increased the bioavailability of orally administered delphinidin-3-rutinoside (18.14 +/- 6.24%). This effect appears to stem immobilization stress by reducing gastrointestinal motility. The cumulative excretion of delphinidin-3-rutinoside and 4'-O-methyl-delphinidin-3-rutinoside in urine and bile was 2.67 +/- 1.24% (w/w) of the dose ingested. Studies report that several metabolites are formed after oral ingestion of anthocyanins. Examples include glucuronyl from cyanidin-3-glucoside and both glucuronyl and sulfate conjugates from pelargonidin-3-glucoside. Our results indicate that delphinidin-3-rutinoside might be metabolized differently from cyanidin-3-glucoside and pelargonidin-3-glucoside.