Beeturia and the biological fate of beetroot pigments beetroot (Beta vulgaris) discoloration of urine asparagus (Asparagus officinalis) odor Allison and McWhirter, 1956 autosomall recessive gene causes red urine after consumption of asparagus A more detailed investigation demonstrated that a quarter of the urine samples collected from 86 volunteers after beetroot ingestion were subjectively (visually) detected as positive, with an additional group being objectively confirmed positive by spectrophotometry as the power of resolution increased. This simple observation has en- abled the conclusion that the creation of separate ‘excretor’ and ‘nonexcretor’ categories (a polymorphism) within this continuous spread of excretion, although convenient, was subjective and artificial. Nonexcretors simply produce too little pigment to be visible to the unaided eye (Pearcy et al., 1992; Mitchell, 1996). This was corrobo- betacyanins chromophore pigments polymethylene cyanine grouping within the aglycone betanidin (and isobetanidin, its epimer at the C-15 position) which is usually conjugated with glucose (Harmer, 1980) yellow colorants (betaxanthines) are known to behave as a redox acid/base indicators and are structurally unstable at the extremes of pH, loosing their color in alkaline conditions and undergoing irreversible decomposition (red to yellow) in acid solution. Optimal stability exists between pH 4 to 5 (von Elbe et al., 1974; Huang and von Elbe, 1987; Watts et al., 1993; Eastwood and Nyhlin, 1995). If the pigment is present, therefore, the resulting color intensity is dependent upon the urinary pH. The red coloration also increased on exposure to sunlight due to pigment rearrangement (Watts et al., 1993) but decreased on storage (Eastwood and Nyhlin, 1995), and repeated freeze-thaw cycles were shown to increase the rate of color loss (Pearcy et al., 1992). vermeil urine demonstrated Chromatographic examination of such vermeil urine demonstrated that the red coloration was due to unchanged beetroot pigments (R. M. Pearcy, unpublished data; Watts et al., 1993). This indicates that once absorbed the pigments were not metabolized but rapidly excreted via the kidneys, and this conjecture has been supported by evidence from rats wherein intravenous or intraperitoneal injection of beetroot ex- tracts demonstrated a high renal clearance (Krantz et al., 1980; Watts et al., 1993; Eastwood and Nyhlin, 1995). Also, there exists an anecdotal report of a volunteer, known not to produce red urine after ingesting betanin, who was shown to excrete rufescent urine when betanin was injected intravenously (Watson et al., 1963). i beeturia phenomenon In addition to being decolorized by hydrochloric acid, beetroot pigments also become achromatic in the presence of ferric ions and rat colonic bacterial preparations but not with saliva, pancreatic, or mu- cosal enzymes (Eastwood and Nyhlin, 1995). These workers reported that the oral ingestion of beetroot pigment together with oxalic acid can produce beeturia in previous nonexcretors and suggested that oxalic acid and ascorbic acid, both found in beetroot, could act as protective factors limiting the degradation of pigment in stomach acid. This combination (beetroot pigment plus oxalic acid) produced a bright red ileostomy effluent but did not produce beeturia in ileostomy patients, indicating that pigment absorption occurs mainly in the colon. They concluded, adding to the “stomach acid hypothesis”, that coingestion of oxalic acid is able to protect the pigment during its travel to the colon; otherwise, the pigment is decolorized in nonbee- turic individuals by nonenzymatic processes in the stomach and colon (Eastwood and Nyhlin, 1995). oxalic acid and ascorbic acid beetroot pigment + oxalic acid beetroot pigment ------------------------- Temperature-dependent Expression of Betacyanin Synthesis in Amaranthus Seedlings Our findings suggest that, in suspension-cultured cells of Portulaca, an MJ-mediated signal transduction pathway prominently exists in betacyanin synthesis. betanidin 5-O-beta-glucosyltransferase (EC 2.4.1). Synthesis of betanin from betanidin and UDP-glucose by a protein preparation from cell suspension cultures of Dorotheanthus bellidiformis (Burm. f.) N. E. Br. Abstract Protein preparations from cell-suspension cultures of Dorotheanthus bellidiformis (Aizoaceae) catalyzed the formation of betanin (betanidin 5-O-glucoside) from betanidin and uridine 5prime-diphosphate(UDP)-glucose. The enzyme activity can be classified as UDP-glucose: betanidin 5-O-beta-glucosyltransferase (EC 2.4.1).