Structure and semisynthesis of platensimide A, produced by Streptomyces platensis

Platensimycin and platencin are novel natural product antibiotics that inhibit bacterial growth by inhibiting condensing enzymes FabF and FabF/FabH of fatty acid biosynthesis pathways, respectively. Continued search for the natural congeners of these compounds led to the isolation of platensic acid, the free C-17 tetracyclic enoic acid, and platensimide A, a 2,4-diaminobutyric acid amide derivative. Isolation, structure, semisynthesis, and activity of these compounds are described.     

Structure determination of lepidopteran,self-defense substance produced by silkworm

The structure of lepidopteran was determined by sequential analysis using the Edman method for the whole molecule as well as several fragment peptides obtained by enzymatic and chemical cleavages. Consequently, lepidopteran was found to be a mixture of congeners composed of 35 amino acids possessing one replaceable amino acid residue of lysine with δ-hydroxylysine.     

Cladoniamides A-G, tryptophan-derived alkaloids produced in culture by Streptomyces uncialis

Cladoniamides A-G (3- 9) have been isolated from cultures of Streptomyces uncialis, and their structures have been elucidated by a combination of spectroscopic analysis and an X-ray diffraction analysis of cladoniamide A (3). The cladoniamides have unprecedented rearranged and degraded alkaloid skeletons with putative biogenetic origins from indolocarbazole precursors. Cladoniamide G (9) is cytotoxic to MCF-7 cells in vitro at 10 microg/mL.     

Some rheological properties of the extracellular polysaccharide produced byVolcaniella eurihalina F2-7

Volcaniella eurihalina strain F2-7 synthesizes an exopolysaccharide named V2-7, primarily composed of glucose, mannose, and rhamnose. The effect of chemical and physical factors on solution viscosity was studied. The V2-7 EPS showed pseudoplastic behavior at concentrations over 0.5% w/v. Viscosity decreased with temperature, but the viscosity values were restored after cooling. Freeze-thawing treatment did not affect the rheological properties of its solutions. Addition of inorganic salts produced a diminution of viscosity. However, the most remarkable aspect of V2-7 EPS is the effect of pH on its solutions; it is able to form high viscosity solutions, like a gel, at low pH values even in the presence of inorganic salts. This property, not present in neutral and alkaline solutions, makes it potentially useful for various industrial applications.     

Total synthesis of lepidopteran A,self-defence substance produced by silkworm.

Lepidopteran, self-defence substance produced by silkworm (Bombyx mori), was synthesized by the solution method for confirmation of the proposed structure.     

Effect of peroxide depolymerization of chitosan on properties of chitosan sulfate particles produced from this substance

Effect of the oxidative destruction of chitosan on the rate at which a dispersed phase is formed in its dilute solutions in the presence of sulfate ions and on the composition, size and ζ-potential of submicrometer chitosan sulfate particles being formed was studied. It was found that the particle size steadily decreases as the molecular mass of chitosan becomes smaller, and the sedimentation stability of aqueous dispersions increases in the absence of surfactants. The \(\nu _{SO_4 } :\nu _{NH_2 }\) molar ratio in chitosan sulfate particles is independent of the molecular mass of chitosan and varies within the range 0.45–0.46. A pH-dependence of the sign of the ζ-potential with isoelectric point at pH 5.0 was found for particles based on destructed chitosan.     

Measurement of ascorbic acid and dehydroascorbic acid in gastric juice by HPLC

New methods are presented for measuring total vitamin C and the ascorbic acid/dehydroascorbic acid ratio in gastric juice. Extracts are prepared from a gastric juice which are suitable for direct injection onto a Waters Nova-pak C18 Radial-pak cartridge for high performance liquid chromatography (HPLC) using ultraviolet absorbance at 270 nm for detection. Both enable removal of interfering mucus and mucopolysaccharide breakdown products in a novel way. The first uses mini-columns of Sephadex G-50, run in acidic conditions to remove large molecular weight material while maintaining the ascorbic acid/dehydroascorbic acid ratio as it was in the fresh sample. Addition of dithiothreitol converts the dehydroascorbic acid quantitatively to ascorbic acid, thus enabling measurement of both components. The second method converts all the dehydroascorbic acid to ascorbic acid at the outset. A perchloric acid extract is neutralized and passed through a Sep-Pak C18. A new internal standard, reductic acid, is introduced for ascorbic acid analysis which behaves identically on Sep-Pak C18. Samples are analysed by ion-pair chromatography using 0.02 M NH4H2PO4 buffer (pH 7.1): methanol (80:20 v/v) containing 0.62 g/L tetrapentylammonium bromide. The detection limit was 1 ng ascorbic acid, and chromatography was completed in 5 min. The values obtained by the two independent HPLC methods were in good agreement with each other and with those obtained by the 2,4-dinitrophenylhydrazine colorimetric method.     

Identification of a new antifungal oligoacetal derivative produced by Streptomyces toxytricini against Candida albicans

Thirty actinomycete isolates were isolated from soil and tested against Candida albicans in vitro. The active isolate was identified by 16s-rRNA gene sequencing method as Streptomyces toxytricini. The antifungal compound was extracted with ethyl acetate followed by diethyl ether. Both HPLC and GC–MS analysis confirmed presence of one pure compound in the diethyl ether extract. The compound is a yellow liquid has a maximum absorbance at 240 nm in methanol. The chemical structure was elucidated by 1D and 2D-NMR and IR analyses. The elucidated molecular formula was C₃₆H₅₄O₁₄. The compound is a polyacetal tricyclononane derivative, composed of a tricyclononane ring attached from the carbon atom number four with an oligo-acetal chain (six acetal groups in chain) and from the carbon atom number seven with a methoxy carbonyl benzene-1,3-dicarboxylic acid. The purposed name is: 4- {[tricycle(3.2.1.1^1,3)non-8-yl] methoxy carbonyl benzene-1,3-dicarboxylic acid} (2,4,5,6,7,8,9 heptaoxa, 3-ethoxy, 5,6,7,9-tetramethyl unidecane).     

Structure determination of lepidopteran c,self-defence substance produced by silkworm (bombyx mori)

Lepidopteran C is a minor component in a group of lepidopterans which are self-defence substances produced in haemolymph of silkworm. Its structure was determined by the Edman degradation of the whole molecule as well as the fragments obtained by digestion of Staphylococcus aureus V8 protease, proline specific endopeptidase, and trypsin. Although lepidopteran C is similar to A in amino acid sequence, 11 amino acids of A are substituted in the sequence of C.