Betty W. Li

Chemical-ionization mass spectra of per-O-acetyl-aldononitriles and methylated aldononitrile acetates

Per-0-acetylaldononitriles have been used as derivatives for the separation and identification of mixture of aldoses by gas-liquid chromatography (~.I.c.)‘*~ and by gas-liquid chromatography--mass spectrometry3-‘. Electron-impact mass spectrometry (e.i.-m.s.) does provide characteristic peaks from the aldononitrile peracetates for ready interpretation, although it seldom yields the molecular ion. The research reported here describes analysis of per-0-acetylaldononitriles by chemicalionization mass spectrometry 6. In contrast to the electron-impact spectra, where molecular ions are not normally seen, chemical-ionization spectra show M+ 1 peaks in each instance. The base peak in each spectrum is at (M + 1) 60 and results from the loss of the elements of acetic acid from tie per-O-acetylaldononitriles. A mixture containing the aldononitrile peracetates from D-rhamnose (l), Lfucose (2), D-arabinose (3), D-xylose (d), D-mannose (3, D-gluCOSe (6), and D-galactose (7) was separated and analyzed by g.l.c.-c.i.-m.s. The chromatographic nonseparalion of 2 and D-ribose (8) is resolved by the m.s., which permits separation of the ions characteristic of each component (Table I). G.1.C. was performed on a mixed liquid-phase consisting of 3% of OV-225 and 2.5% of tetramethylcyclobutanediol succinate on SO-100 mesh Supelcoport, with helium (20 ml/min) as the carrier gas: this system provides two major benefits: short retention-times nnd minimal bleeding of the liquid phase into the detection system. For all of the foregoing aldononitrile peracetates, relative intensities of principal ions and their mass-to-charge ratios (in/e values) are reported in Table I. Methylation of laminaran according to Lindberg’ gave a mixture of partially methylated sugars that was converted by hydrolysis and derivatization into 3,5,6-tri0-acetyl-2,4-di-0-methyl-D-glucononitrile (9), 3,5-di-0-acetyl-2,4,6-tri-O-methyl-D-

Analysis of individual foods for the validation of sugars and starch contents of composited diets

Abstract Two similar total daily diets were collected for each of three caloric levels. From these, six diet composites and the 21 commonly eaten individual foods which made up the composites were analyzed for their sugar and starch contents. Sugars were extracted into 80% methanol. Extracts were dried, derivatized, and analyzed by gas-liquid chromatography (GLC). The residue after methanol extraction was incubated with an enzyme/buffer solution for starch hydrolysis and the resulting glucose was again determined by GLC. From the data, the sum of all sugars (i.e., fructose, glucose, lactose, maltose, sucrose) and the amount of starch as calculated from the analyzed values for each individual food are comparable to values obtained simply by analyzing the composited total diets. This finding validates the analyzed “available carbohydrate” data of composites. However, a large variation was found between analyzed “available carbohydrate” and calculated “total carbohydrate” values from food tables.

Dietary Guidelines/RDA/Daily Value Workshop

A recommended dietary allowance (RDA) should be established for total dietary fiber (TDF) in the next edition of the National Academy of Sciences Report on recommended intakes. Sufficient scientific evidence is available to warrant advice on, at least, the upper and lower limits of fiber intake consistent with health. An RDA needs to be established for fiber intake to guide the development of Daily Values, used in the Nutrient Facts on food labels as well as the development of Dietary Guidelines for Americans.

Effect of high dietary thiamin on copper deficiency symptoms of rats fed a high-fructose, low-copper diet

The consumption of diets high in fructose may increase the dietary requirement for thiamin since the coenzyme form of thiamin functions primarily in the metabolism of 2-keto sugars. Also, a thiamin x copper interaction has been reported which may be beneficial to an animal consuming a low-copper diet. Therefore, the purpose of this study was to examine the effect of high dietary thiamin on copper deficiency symptoms of rats fed a high-fructose, low-copper diet. Rats were divided into two dietary groups of different thiamin levels: 6 mg thiamin/kg diet, high-fructose, low-copper or 60 mg thiamin/kg diet, high-fructose, low-copper. Mortality rate of rats fed a low copper diet was not greatly improved by dietary thiamin. Body weight was significantly reduced in the high-thiamin, high-fructose, low-copper dietary group. Supplementing with high dietary thiamin did not improve tissue weights of rats fed high-fructose, low-copper diets. Hematocrit, RBC superoxide dismutase activity, plasma ceruloplasmin activity, plasma Cu levels and hepatic Cu levels were not improved by supplementing high-fructose, low-copper diets with high thiamin levels. These results suggest that high dietary thiamin does not interact with copper to improve the symptoms of copper deficiency.