Many tropical fruits are rich in anthocyanins, though limited information is available about the characterization and quantification of these anthocyanins. The identification and quantification of anthocyanin pigments in four tropical fruits were determined by HPLC-MS/MS. Fruits studied included acerola (Malphigia emarginata), jussara (Euterpe edulis), jambolão (Syzygium cumini), and guajiru (Chrysobalanus icaco). All four fruits were found to contain anthocyanin pigments. Anthocyanidin backbones included cyanidin, delphinidin, peonidin, pelargonidin, petunidin, and malvidin. Guajiru contained several acylated forms, while acerola, jussara, and jambolão contained only nonacylated glycosides. These results demonstrate that these tropical fruits are rich in anthocyanins and that the anthocyanins are widely ranging in anthocyanidin backbone, glycosylation, and acylation.

Coenzyme B 12 (Ado-Cbl) and vitamin B 12 (CN-B 12 ) (Fig. 1) include the base 5,6-dimethylbenzimidazole (DMB) as an ␣-axial ligand. Prokaryotes, the only producers of vitamin B 12 , make "complete" corrinoid cofactors with a variety of alternative ␣-axial ligands, including benzimidazoles, phenols, and purines (16, 52). These alternative corrinoids may be functional equivalents of coenzyme B 12 for many bacterial enzymes, but functional differences are suggested by the selectivity of the human assimilatory protein, intrinsic factor for cobalamin, the DMB-containing vitamin B 12 (53).Under strictly anaerobic growth conditions, Salmonella enterica synthesizes corrinoids de novo (44) and installs either adenine (to form pseudo-coenzyme B 12 [Ado-pseudo-B 12 ]) or 2-methyl-adenine (to form adenosyl-factor A) as an ␣-axial ligand (22). If even trace amounts of oxygen are present, DMB-containing B 12 (cobalamin [Cbl]) is also made (39). When grown aerobically on glucose, S. enterica cannot synthesize the corrin moiety, which must be supplied as an "incomplete" corrinoid, such as cobinamide (Cbi), with its corrin ring and aminopropanol side chain. Under these conditions, coenzyme B 12 is made, with DMB as the ␣-axial ligand (20). Figure 2 diagrams the de novo (anaerobic) synthetic pathway and assimilation of exogenous Cbi or . Notice that the ␤-ligand adenosyl can be added (by CobA) to three different substrates and that the (CN) 2 Cbi supplied as the corrin ring source is not a normal CobA substrate.Here, the origins and installation of ␣-axial ligands are approached genetically using an unexpected feature of S. enterica. While S. enterica can use exogenous Cbi to produce B 12 cofactors (cobalamins) during aerobic growth on glucose (20), it makes only about 100 molecules per cell (2). This is apparently insufficient B 12 coenzyme to support growth on ethanolamine (5) unless the DMB base is also supplied. That is, under these conditions, cells neither make sufficient DMB nor install an alternative ligand to allow corrinoid-dependent aerobic growth on ethanolamine (5).This situation allowed positive selection of mutants that can grow on ethanolamine plus Cbi without added DMB. These mutants were expected to show either increased endogenous DMB production or to install an alternative base as an ␣-axial ligand. All of the mutants made pseudo-B 12 cofactors, which have adenine as an ␣-axial ligand, and most of these mutations affected purine metabolism so as to increase the intracellular level of free adenine base. The same set of enzymes (CobUSTC) installs either adenine base (to form pseudo-B 12 ) or DMB (to form vitamin B 12 ). A model suggests how the choice is made. MATERIALS AND METHODSBacterial strains and transposons. Strains were derived from S. enterica (serovar Typhimurium) LT2

A clinical study was conducted to investigate the dose response and metabolism of strawberry anthocyanins. In a crossover study design, 12 healthy adults consumed each of 3 strawberry treatments. The treatments were 100 g, 200 g, and 400 g of pureed strawberries, delivering 15 micromol, 30 micromol, and 60 micromol anthocyanin, respectively. Urine samples were collected for 24 h after each dose and samples were analyzed by HPLC with diode array detection and ion trap MS. Pelargonidin 3-glucoside was the major anthocyanin form in the treatments, and pelargonidin 3-glucoside and 3 metabolites of pelargonidin 3-glucoside (detected as monoglucuronides) were excreted in urine after ingestion. One predominant monoglucuronide form was detected in urine in masses 10-fold higher than the other 2 monoglucuronide forms. Increasing dose resulted in increasing appearance of anthocyanins in urine, and the mass of each pelargonidin monoglucuronide increased in urine with increasing dose. These results suggest that pelargonidin 3-glucoside absorption and metabolism are not saturated at masses < or = 60 micromol, thus showing that more strawberry anthocyanin can be absorbed with increasing dose.