Dual fluorophore-nitroxide probes for analysis of vitamin C in biological liquids.

A new method for quantitative analysis of vitamin C in biological and chemical liquids was proposed. The method is based on the use of dual molecule consisting of a fluorescent chromophore and a nitroxide radical. In the dual molecule, the nitroxide acts as a quencher of the fluorescence of the chromophore fragment. Reduction of the nitroxide fragment by ascorbic acid results in decay of ESR signal and enhancement of the fluorescence. By performing the series of pseudo-first-order reactions between the dual molecule and ascorbic acid and consequent plotting rate constants versus ascorbic acid concentrations the calibration curves for the vitamin C analysis were obtained. Variations of chemical structure of fluorophore and nitroxide fragments allow to regulate fluorescent properties and redox potentials of the dual molecules. The proposed fluorophore-nitroxide hybrids retain all features of the spin labels and fluorescence probes gaining new advantages for monitoring redox reactions and radical processes by two independent techniques: ESR and steady-state fluorescent spectroscopy. The method was applied to the vitamin C analysis in commercial fruit juices.

Therapeutic effects of substances occurring in higher Basidiomycetes mushrooms: a modern perspective.

This review highlights some of the recently isolated and identified substances of higher Basidiomycetes mushrooms origin that express promising antitumor, immune modulating, cardiovascular and hypercholesterolemia, antiviral, antibacterial, and antiparasitic effects. Medicinal mushrooms have a long history of use in folk medicine. In particular, mushrooms useful against cancers of the stomach, esophagus, lungs, etc. are known in China, Russia, Japan, Korea, as well as the U.S.A. and Canada. There are about 200 species of mushrooms that have been found to markedly inhibit the growth of different kinds of tumors. Searching for new antitumor and other medicinal substances from mushrooms and to study the medicinal value of these mushrooms have become a matter of great significance. However, most of the mushroom origin antitumor substances have not been clearly defined. Several antitumor polysaccharides such as hetero-beta-glucans and their protein complexes (e.g., xyloglucans and acidic beta-glucan-containing uronic acid), as well as dietary fibers, lectins, and terpenoids have been isolated from medicinal mushrooms. In Japan, Russia, China, and the U.S.A. several different polysaccharide antitumor agents have been developed from the fruiting body, mycelia, and culture medium of various medicinal mushrooms (Lentinus edodes, Ganoderma lucidum, Schizophyllum commune, Trametes versicolor, Inonotus obliquus, and Flammulina velutipes). Both cellular components and secondary metabolites of a large number of mushrooms have been shown to effect the immune system of the host and therefore could be used to treat a variety of disease states.

New approaches to synthesis of stereospecific sphingomyelin.

Enormous progress in the asymmetric synthesis of stereochemically and chemically pure D-erythro-sphingosine and ceramides led to the development of a practical, efficient, easily scaleable process to provide industrial quantities of chiral sphingosine and ceramides. This established a new platform of chiral starting materials which facilitate the synthesis of complex sphingolipids. Utilizing stereochemically homogeneous, fully synthetic ceramides, two efficient synthetic methods were developed for the preparation of ultra pure stereochemically homogeneous sphingomyelins. The first method adapted highly efficient phosphoramidite technology from oligonucleotide chemistry. This method allows selective insertion of a phosphocholine moiety into 3-O-protected ceramide through phosphitylation, followed by choline attachment, phosphite oxidation and deprotection. This route provides stereochemically homogeneous sphingomyelin in 35-79% yield. The second route is based on the reaction of selectively protected ceramides with cyclic chlorophosphate followed by treatment with trimethylamine to give the desired sphingomyelins in 50% yield. Multigram quantities of 14C-labeled N-palmitoyl-D-erythro-sphingomyelin were produced with specific activity > 1000 dpm/nmol.

Elucidation of the sequence-specific third-strand recognition of four Watson-Crick base pairs in a pyrimidine triple-helix motif: T.AT, C.GC, T.CG, and G.TA.

We report a specific pattern of recognition by third-strand bases for each of the four Watson-Crick base pairs within a pyrimidine triple-helix motif as determined by PAGE: T.AT, C.GC, T.CG, and G.TA. Our recognition scheme for base triplets is in agreement with previous studies. In addition, we identified another triplet, T.CG, under physiological conditions, in which formation of triple helix was observed at equimolar ratios of the third strand and duplex target. Although different nearest-neighbor effects are expected, this finding extends the base-recognition code to all 4 base pairs in double-stranded DNA under physiological conditions. Base-composition analysis of putative triplex species provided independent evidence for the formation of triplex and confirmed the base-recognition code determined by PAGE. Moreover, the formation of triplex, as detected by gel electrophoresis, was seen to be an all-or-none phenomenon, dependent upon a single-base mismatch among 21 nucleotides. This result suggests a high specificity for the recognition of double-stranded DNA by a third strand. In addition, we report the surprising finding that triplex stability depends on the length and sequence of the target duplex DNA.

Animal and cellular models of sphingolipid storage disorders of humans.

The synthesis of L-galactosylceramide is described. Data are presented indicating that this enantiomorph of D-galactocerebroside is not cleaved by galactocerebroside-beta-galactosidase obtained from mammalian tissues. The synthesis of L-glucosylceramide and beta-D-glucothiocerebroside are outlined. These compounds are also refractory to catabolism by glycosidases in mammalian tissues that catalyze the hydrolysis of naturally occurring cerebrosides. L-Hexosyl- and thioanalogs of cerebrosides and perhaps psychosines as well may be helpful for investigating the pathogenesis of Krabbe's disease and Gaucher's disease.

Animal and cellular models of Gaucher's disease. I. Refractoriness of thio analogs of glucocerebroside to enzymatic hydrolysis.

In order to develop a nonmetabolizable analog of glucocerebroside to investigate the distribution and accumulation of this lipid in model systems, thiohemiacetal derivatives were synthesized and their susceptibility to enzymatic hydrolysis by purified human placental glucocerebrosidase was examined. Sulfur analogs were found to be completely refractory to the activity of this enzyme, indicating their potential use in animal and isolated cell models and possibly for the preparation of affinity chromatography columns for the isolation of glucocerebrosidase.

Reverse Königs-Knorr reaction. Synthesis of beta-D-gluco-thio-cerebroside.

The synthesis of 1-thio-beta-D-glucocerebroside by reaction of 1-iodo-3-O-benzoylceramide with 1-mercapto-beta-D-glucopyranose in the presence of sterically hindered amine (DBU) is described.