A summary of the ion types observed in the Fast Atom Bombardment Mass Spectrometry (FAB-MS) and collision induced decomposition (CID) MS/MS spectra of glycoconjugates (glycosphingolipids, glycopeptides, glycosides and carbohydrates) is presented. The variety of product ion types that arise by cleavages within the carbohydrate moieties has prompted us to introduce a systematic nomenclature to designate these ions. The proposed nomenclature has been developed primarily for FAB-MS, but can be used as well for other ionization techniques [field desorption (FD), direct chemical ionization (DCI), laser desorption/Fourier transform (LD/FT), etc.], and is applicable to spectra recorded in either the positive or negative ion mode during both MS and MS/MS experiments. Ai, Bi and Ci labels are used to designate fragments containing a terminal (nonreducing end) sugar unit, whereas Xj, Yj and Zj represent ions still containing the aglycone (or the reducing sugar unit). Subscripts indicate the position relative to the termini analogous to the system used in peptides, and superscripts indicate cleavages within carbohydrate rings. FAB-MS/MS spectra of a native glycosphingolipid and glycopeptide, and a permethylated ganglioside are shown as illustrations.

A systematic nomenclature for carbohydrate fragmentations in FAB-MS/MS spectra of glycoconjugates

Saponins occur widely in plant species and exhibit a range of biological properties, both beneficial and deleterious. This review, which covers the literature to mid 1986, is concerned with their occurrence in plants and their effects when consumed by animals and man. After a short discussion on the nature, occurrence, and biosynthesis of saponins, during which the distinction between steroidal and triterpenoid saponins is made, the structures of saponins which have been identified in a variety of plants used as human foods, animal feedingstuffs, herbs, and flavorings are described. Many of these compounds have been characterized only during the last 2 decades, and modern techniques of isolation, purification, and structural elucidation are discussed. Particular consideration is given to mild chemical and enzymatic methods of hydrolysis and to recent developments in the application of NMR and soft ionization MS techniques to structural elucidation. Methods currently used for the quantitative analysis of saponins, sapogenols, and glycoalkaloids are critically considered; advances in the use of newer methods being emphasized. The levels of saponins in a variety of foods and food plants are discussed in the context of the methods used and factors affecting these levels, including genetic origin, agronomic, and processing variables, are indicated. Critical consideration is given to the biological effects of saponins in food which are very varied and dependent upon both the amount and chemical structure of the individual compounds. The properties considered include membranolytic effects, toxic and fungitoxic effects, adverse effects on animal growth and performance, and the important hypocholesterolemic effect. A final section deals briefly with the pharmacological effects of saponins from ginseng, since use of this plant is increasing in certain sections of western society as well as being traditional in the Orient.

The chemistry and biological significance of saponins in foods and feedingstuffs.

Curie-point pyrolysis-capillary gas chromatography-high-resolution mass spectrometry of microcrystalline cellulose

A correlation is found between the fragment ion yield and the degree of branching for oligosaccharides analyzed by matrix assisted laser desorption ionization/Fourier transform mass spectrometry (MALDI/FTMS). The most branched oligosaccharides produced the least amount of fragment ion. Another relationship is found between the size of the alkali metal ion and the yields of fragment ions. The smallest alkali metal ion produced the greatest amount of fragment ions. The presence of the quasimolecular ion is dependent on both the size of the metal ion and the size of the sugar. A minimum number of saccharide residues are necessary to stabilize the complex and produce a quasimolecular ion. Molecular mechanics calculations were performed and structures obtained consistent with the observed experimental behavior. The site of coordination plays a dominant role in the yield and types of fragment ions observed.

Coordination of Alkali Metals to Oligosaccharides Dictates Fragmentation Behavior in Matrix Assisted Laser Desorption Ionization/Fourier Transform Mass Spectrometry

Fourier transform ion cyclotron resonance mass spectrometry: the teenage years

Fourier transform mass spectrometry: current status

Des dechets chimiques liquides et solides de solutions aqueuses lyophilisees sont volatilises directement dans la source d'ions d'un instrument triple quadrupole. Les limites de detection sont de l'ordre de 10 a 100 ppb

Scheme for the Direct Analysis of Organics in the Environment by Tandem Mass Spectrometry

Laser-desorption Fourier transform mass spectra of polysaccharides.

Laser desorption mass spectra of malto-oligomers, including starch, have been obtained using Fourier transform mass spectrometry. Fragmentations of these oligomers have been examined after doping with metal salts to obtain cation-attachment ions. Doping starch with NaCl, KBr and Ag2O results in analogous cation-attachment oligosaccharide fragment ions for all three metal ions. A distinct and unusual fragmentation pattern is observed for the larger oligomers.

Laser desorption Fourier transform mass spectra of malto-oligosaccharides.

Positive- and negative-ion mass spectra of five glycoconjugates were obtained using laser desorption/Fourier transform mass spectrometry. These were the glycoalkaloids alpha-solanine and alpha-tomatine and the steroid glycosides gitoxin, lanatoside A and digitonin. Doping with KCl yielded both potassium- and chloride-attachment ions. Few fragment ions were observed for these species, with the exception of digitonin, although the negative-ion spectra showed relatively more fragmentation than the positive-ion spectra. All major fragments appeared to arise from losses of sugar groups due to cleavages at the glycosidic linkages. This contrasted sharply with the behavior of the malto-oligosaccharides studied in this laboratory.

Mildred L. Coates

Papers

Fourier transform mass spectrometry: current status

Scheme for the Direct Analysis of Organics in the Environment by Tandem Mass Spectrometry

Laser-desorption Fourier transform mass spectra of polysaccharides.

Laser desorption Fourier transform mass spectra of malto-oligosaccharides.

Laser desorption/Fourier transform mass spectra of glycoalkaloids and steroid glycosides.