[New ceramides from sea sponge Oceanapia sp].

Total ceramides containing nonbranched and iso-branched C18- and C19-phytosphingosines acylated with non-hydroxylated fatty acids were isolated from a marine sponge Oceanapia sp. The structures of these compounds were determined by HPLC, NMR, MALDI-TOF MS, and GLC-MS of the Me3Si derivatives and by chemical transformations. The English version of the paper: Russian Journal of Bioorganic Chemistry, 2006, vol. 32, no. 3; see also http://www.maik.ru.

Spongiadioxins A and B, two new polybrominated dibenzo-p-dioxins from an Australian marine sponge Dysidea dendyi.

Two new cytotoxic tetrabromodibenzo-p-dioxins, spongiadioxins A (1) and B (2), were isolated from an Australian marine sponge Dysidea dendyi. The structures of these compounds were established by 1D and 2D NMR spectroscopy, X-ray analysis of the methyl ether of spongiadioxin A (3), and synthesis of the methyl ether of spongiadioxin B (4) from diphenyl ether (9) isolated from Dysidea herbacea.

Shikonin production by p-fluorophenylalanine resistant cells of Lithospermum erythrorhizon.

Studies were conducted with a BK-39 callus culture of Lithospermum erythrorhizon, which produced seven shikonin derivatives (acetylshikonin, propionylshikonin, isobutyrylshikonin, beta,beta-dimethylacrylshikonin, isovalerylshikonin, beta-hydroxyisovalerylshikonin and alpha-methyl-n-butyrylshikonin). A selection of cell aggregates of BK-39 culture on a medium containing p-fluorophenylalanine (PFP) yields a cell line possessing a higher resistance to the inhibitor than the initial culture. Selected BK-39F cultures produced almost the same profile of shikonin naphthoquinones as the initial culture. The shikonin derivative content of PFP-resistant culture was approximately two times higher than that of the control, reaching 12.6% of DW cell biomass.

Synthesis of ginsenoside Rg3, a minor constituent of Ginseng radix.

Glycosylation of 12beta-acetoxy-dammar-24-en-3beta,20(S)-diol (4), with hepta-O-acetyl-alpha-sophorosyl bromide (5) under catalysis by Ag2CO3 or Ag2O afforded a chromatographically unseparated mixture of the alpha- and beta-linked octaacetates 6 and 7 in an approximately 2.5:1 ratio. After deprotection and chromatographic purification, the free alpha- (8) and beta-glycosides (9) were obtained. Sophoroside 9 was identical in all respects with ginsenoside Rg3, the minor component of Ginseng Radix rubra. All compounds were fully characterized by 1H and 13C NMR spectroscopy.

[Kidney sorbitol dehydrogenase: kinetic mechanism]. / Sorbitoldegidrogenaza pochki: kineticheskii mekhanizm.

Properties of sorbitol dehydrogenase isolated from rat kidney were studied. Sorbitol dehydrogenase reactions followed the consecutive irregular order as shown in studies of kinetic patterns, inhibition by end products and thermoinactivation of the enzyme in the presence of substrates.

[Changes in the intracellular glucose-6-phosphate dehydrogenase metabolism in the rat liver during thiamine deficiency]. / Izmeneniia vnutrikletochnogo krugooborota gliukozo-6-fosfatdegidrogenazy pecheni krys pri nedostatochnosti tiamina.

Patterns of intracellular glucose-6-phosphate dehydrogenase turnover were studied in liver tissue of intact and thiamin-deficient rats using a new procedure for the enzyme purification. The alternations, found in the half-life period, in constant rates of synthesis and degradation of the key enzyme of the pentosephosphate pathway, correlated with a decrease of the glucose-6-phosphate dehydrogenase activity in vitamin B1 deficiency.

[Regulation of glucose-6-phosphate dehydrogenase activity of the rat liver in vitamin B1 deficiency]. / O reguliatsii aktivnosti gliukozo-6-fosfatdegidrogenazy pecheni krys pri B1-nedostatochnosti.

Kinetic patterns and thermostability of glucose-6-phosphate dehydrogenase, isolated from liver tissue of intact and thiamine-deficient rats, were analyzed. Distinct alterations were not found in the patterns studied. The data obtained suggest that a decrease in the enzymatic activity, observed after administration of oxythiamine into rats, occurred due to lowering in content of the protein active form.

A study of the reaction catalysed by alginate lyase VI from the sea mollusc, Littorina sp.

The molecular weight of polymeric alginic acid digested by alginate lyase (poly(1,4-beta-D-mannuronide) lyase, EC 4.2.2.3) was determined at various stages of the lysis. Low molecular weigh fragments were detected only after 60-100% lysis. Some high molecular weight fragments remained intact even after addition of a fresh aliquot of enzyme to the digest. The enzyme showed maximal activity at pH 5.6 in 0.05 M salt. Enzyme activity was stimulated by addition of 7.5 mM CaCl2 and 0.2 M NaCl, when the pH optimum was between 8 and 8.5. Only mannuronic acid was detected at the reducing end of fragments after exhausive enzymolysis, reduction and hydrolysis. On studying the reaction products by NMR, a double-bound signal (sigma = 5.98 ppm) was observed. A considerable decrease in intensity of the D-mannuronic acid residue signal was detected after hydrolysis of alginate lyase VI on poly-(ManUA-GulUA), but not poly(GulUA). The results suggest that alginate lyase VI may be an endoalginate lyase that splits glycoside bonds only between two mannuronic acid residues.