Effect of xylitol on growth of Streptococcus pneumoniae in the presence of fructose and sorbitol. (17/793)

Xylitol is effective in preventing acute otitis media by inhibiting the growth of Streptococcus pneumoniae. To clarify this inhibition we used fructose, which is known to block similar growth inhibition observed in Streptococcus mutans. In addition, we evaluated the efficacy of sorbitol in inhibiting the growth of pneumococci, as sorbitol is widely used for indications similar to those for which xylitol is used. The addition of 5% xylitol to the growth medium resulted in marked growth inhibition, an effect which was totally eliminated in the presence of 1, 2.5, or 5% fructose but not in the presence of 1 or 5% glucose, 1% galactose, or 1% sucrose. This finding implies that xylitol-induced inhibition of pneumococcal growth is mediated via the fructose phosphotransferase system in a way similar to that in which mutans group streptococcal growth is inhibited. The addition of sorbitol at concentrations of 1, 2.5, or 5% to the growth medium did not affect the growth of pneumococci and neither inhibited nor enhanced the xylitol-induced growth impairment. Thus, it seems that xylitol is the only commercially used sugar substitute proven to have an antimicrobial effect on pneumococci.  (+info)

PROP (6-n-Propylthiouracil) tasting and sensory responses to caffeine,sucrose, neohesperidin dihydrochalcone and chocolate. (18/793)

The genetically determined ability to taste 6-n-propylthiouracil (PROP) has been linked with lowered acceptance of some bitter foods. Fifty-four women, aged 18-30 years, tasted and rated PROP-impregnated filter paper and seven solutions of PROP. Summed bitterness intensity ratings for PROP solutions determined PROP taster status. Respondents also tasted five sucrose and seven caffeine solutions, as well as seven solutions each of caffeine and PROP that had been sweetened with 0.3 mmol/l neohesperidin dihydrochalcone (NHDC). Respondents also rated three kinds of chocolate using 9-point category scales. PROP tasters rated caffeine solutions as more bitter than did non-tasters and liked them less. PROP tasters did not rate either sucrose or NHDC as more sweet. The addition of NHDC to PROP and caffeine solutions suppressed bitterness intensity more effectively for tasters than for non-tasters and improved hedonic ratings among both groups. PROP tasters and non-tasters showed the same hedonic response to sweetened caffeine solutions and did not differ in their sensory responses to chocolate. Genetic taste markers may have only a minor impact on the consumption of such foods as sweetened coffee or chocolate.  (+info)

Small-bowel absorption of D-tagatose and related effects on carbohydrate digestibility: an ileostomy study. (19/793)

BACKGROUND: The ketohexose D-tagatose is a new sweetener with a low energy content. This low energy content may be due to either low absorption of the D-tagatose or decreased absorption of other nutrients. OBJECTIVE: The aims of this study were to measure the excretion of D-tagatose from the human small bowel, to calculate the apparent absorption of D-tagatose, and to study the effects of D-tagatose on the small-bowel excretion of other carbohydrates. DESIGN: A controlled diet was served for 2 periods of 2 d during 3 consecutive weeks to 6 ileostomy subjects. In one of the periods, 15 g D-tagatose was added to the diet daily. Duplicate portions of the diet and ileostomy effluents were freeze-dried and analyzed to calculate the apparent net absorption of D-tagatose and carbohydrates. RESULTS: Median D-tagatose excretion was 19% (range: 12-31%), which corresponded to a calculated apparent absorption of 81% (69-88%). Of the total amount of D-tagatose excreted [2.8 g (1.7-4.4 g)], 60% (8-88%) was excreted within 3 h. Between 3 and 5 h, 32% (11-82%) was excreted. Excretion of wet matter increased by 41% (24-52%) with D-tagatose ingestion. Sucrose and D-glucose excretion increased to a small extent, whereas no significant changes were found in the excretion of dry matter, energy, starch, or D-fructose. CONCLUSIONS: The apparent absorption of 15 g D-tagatose/d was 81%. D-Tagatose had only a minor influence on the apparent absorption of other nutrients.  (+info)

Evaluation of several saccharides as osmotic agent for peritoneal dialysate. (20/793)

OBJECTIVE: The carbonyl group of glucose reacts non-enzymatically with the amino group of protein to form advanced glycosylation end-products (AGEs). AGEs are found in the peritoneum of continuous ambulatory peritoneal dialysis patients, and this AGE formation is suspected to be one of the causes of impaired peritoneal function. In order to control AGE formation in the peritoneum, AGE formation and ultrafiltration in rats were examined with peritoneal dialysates using as osmotic agents saccharides that lack a carbonyl group, the saccharic acid lactobionate [molecular weight (MW) 358.30], the sugar alcohol maltitol (MW 344.32), and the nonreducing sugar nistose (MW 666.58). DESIGN: Bovine serum albumin (BSA) (25 mg/mL) was incubated with 18, 36, and 72 mg/mL maltitol, lactobionate, nistose, and glucose at 37 degrees C. After 3 or 6 weeks, amounts of furosine and N-(carboxymethyl) lysine were measured. A 20-mL intraperitoneal injection of a lactate-based dialysate (osmotic pressure 388 mOsm/kg) containing 4.34% maltitol, 4.52% lactobionate, or 8.4% nistose was given to Sprague-Dawley rats and, after 2, 4, or 6 hours, the quantity of effluent and levels of urea nitrogen and creatinine in the effluent and in serum were measured. RESULTS: No increases in furosine or N-(carboxymethyl) lysine were seen with maltitol, lactobionate, or nistose after 3 and 6 weeks of incubation with BSA; AGE formation was not observed. In the study in rats, the quantity of abdominal fluid after a 6-hour dwell was nistose > lactobionate > maltitol > glucose. No differences in dialysate-to-plasma ratios for urea nitrogen or creatinine were seen in any group. CONCLUSIONS: AGE formation in peritoneal tissue might be controlled by using saccharides with a modified carbonyl group as osmotic agents for peritoneal dialysates. Nistose is considered to yield the most efficient dialysis.  (+info)

Structure-sweetness relationship in thaumatin: importance of lysine residues. (21/793)

To clarify the structural basis for the sweetness of thaumatin I, lysine-modified derivatives and carboxyl-group-modified derivatives were prepared by chemical modification followed by chromatographic purification. The sweetness of derivatives was evaluated by sensory analysis. Phosphopyridoxylation of lysine residues Lys78, Lys97, Lys106, Lys137 and Lys187 markedly reduced sweetness. The intensity of sweetness was returned to that of native thaumatin by dephosphorylation of these phosphopyridoxylated lysine residues except Lys106. Pyridoxamine modification of the carboxyl group of Asp21, Glu42, Asp60, Asp129 or Ala207 (C-terminal) did not markedly change sweetness. Analysis by far-UV circular dichroism spectroscopy indicated that the secondary structure of all derivatives remained unchanged, suggesting that the loss of sweetness was not a result of major disruption in protein structure. The five lysine residues, modification of which affected sweetness, are separate and spread over a broad surface region on one side of the thaumatin I molecule. These lysine residues exist in thaumatin, but not in non-sweet thaumatin-like proteins, suggesting that these lysine residues are required for sweetness. These lysine residues may play an important role in sweetness through a multipoint interaction with a putative thaumatin receptor.  (+info)

Sweet liking and family history of alcoholism in hospitalized alcoholic and non-alcoholic patients. (22/793)

The present study was designed to test the hypothesis that preference for stronger sweet solutions may be associated with the genetic risk for alcoholism. Thirty-two male patients with alcohol dependence admitted for alcoholism in-patient treatment and 25 non-alcoholic control subjects were used in the study. Hedonic response to sweets was evaluated using the sweet preference test. Family history of alcoholism was evaluated using a Russian version of the Michigan Alcoholism Screening Test modified for the assessment of the alcohol-related behaviour of the subject's biological father. Similar to our previous findings, alcoholics were far more likely to prefer the highest offered sucrose concentration (0.83 M), compared to non-alcoholic controls. Such preference was determined by two factors: positive family history of alcoholism and alcoholic status. Statistically, these factors contributed to the likelihood of preferring sweet solutions independently. Therefore, the effects of these factors may enhance each other. These findings support the hypothesis that preference for a stronger sweet solution is associated with a paternal history of alcohol dependence and may reflect a genetic predisposition to alcoholism.  (+info)

Solution structure, backbone dynamics, and stability of a double mutant single-chain monellin. structural origin of sweetness. (23/793)

Single-chain monellin (SCM), which is an engineered 94-residue polypeptide, has been characterized as being as sweet as native two-chain monellin. Data from gel-filtration high performance liquid chromatography and NMR has proven that SCM exists as a monomer in aqueous solution. In order to determine the structural origin of the taste of sweetness, we engineered several mutant SCM proteins by mutating Glu(2), Asp(7), and Arg(39) residues, which are responsible for sweetness. In this study, we present the solution structure, backbone dynamics, and stability of mutant SCM proteins using circular dichroism, fluorescence, and NMR spectroscopy. Based on the NMR data, a stable alpha-helix and five-stranded antiparallel beta-sheet were identified for double mutant SCM. Strands beta1 and beta2 are connected by a small bulge, and the disruption of the first beta-strand were observed with SCM(DR) comprising residues of Ile(38)-Cys(41). The dynamical and folding characteristics from circular dichroism, fluorescence, and backbone dynamics studies revealed that both wild type and mutant proteins showed distinct dynamical as well as stability differences, suggesting the important role of mutated residues in the sweet taste of SCM. Our results will provide an insight into the structural origin of sweet taste as well as the mutational effect in the stability of the engineered sweet protein SCM.  (+info)

A search for new glucophores by isosteric replacement of carboxylic function. (24/793)

We used arylsulfonylalkanoic acids as parent structures for designing new potential sweeteners. The Kohonen maps of the molecular electrostatic potential of the possible bioisosteric replacements of carboxylic function have been simulated and used for the selection of the potential synthetic targets which are now under synthesis.  (+info)