13C-NMR Spectra and Streochemistry of Isoechinulins A,B and C

¹³C-NMR spectra of isoechinulins A, B and C, metabolites from Aspergillus ruber, were fully assigned on the basis of chemical shifts and multiplicities and comparison with their analogues. Taking advantage of the symmetrical structure of the diketopiperazine ring, the stereochemistry of the trisubstituted carbon-carbon double bond in a dehydrotryptophyl moiety was determined as Z (cis) by measuring the coupling constants, , in the proton nondecoupled spectrum of isoechinulin B.     

Some Physicochemical Properties of Invertase of Candida utilis

This study examined the microbial transformation of carbazole (CZ) by an isolated bacterium that can use CZ as a sole carbon and nitrogen source. The strain identified as Pseudomonas stutzeri produced a large amount of anthranilic acid (AA) from CZ in the medium containing a nonionic surfactant. In dialysis culture using ion-exchange resin, 7.9 g/liter (58mm) of AA was accumulated from 15g/liter (90mm) of CZ and the molar yield of AA reached about 64%.     

Isolation and Identification of l-Menthyl-β-d-glucoside from Shubi

Quinoxalines derived from d-galactose with o-phenylenediamine (OPD) in acidic media under reflux were studied by using GLC and NMR measurements. Four quinoxaline derivatives were obtained from the reaction mixture, and were identical with those derived from d-glucose. The yields of 2-(D-lyxo-tetrahydroxybutyl)quinoxaline (GA-III), and the stereoisomeric derivative of GA-III, i.e., 2-(D-arabino-tetrahydroxybutyl)quinoxaline (ATBQ), were 13.2 and 5.3–, respectively. The ratio of GA-III to ATBQ derived from d-galactose was reciprocally coincident with that from d-glucose. Some proposals are made on the relationship between the isomerization of these sugars and the formation of quinoxaline derivatives.     

New Steroidal Glycosides from Rhizomes of Clintonia udensis

A total of 10 steroidal glycosides, together with three new spirostanol glycosides (6–8), a new furostanol glycoside (9), and a new cholestane glycoside (10), were isolated from the rhizomes of Clintonia udensis (Liliaceae). The structures of the new compounds were determined on the basis of extensive spectroscopic analyses, including 2-D nuclear magnetic resonance (NMR) data, and of hydrolytic cleavage followed by chromatographic or spectroscopic analyses. The isolated glycosides were evaluated for their cytotoxic activity against HL-60 leukemia cells. Spirostanol glycosides 1 and 2, and furostanol glycoside 4 showed cytotoxic activity with IC₅₀ values of 3.2±0.02, 2.2±0.12, and 2.2±0.06 μg/ml, respectively. Neither the spirostanol and furostanol saponins with a hydroxy group at C-1 (6 and 9) and C-12 (7 and 8) nor cholestane glycosides (5 and 10) exhibited apparent cytotoxic activity at a sample concentration of 10 μg/ml.     

Purification of Oat Debranching Enzyme and Occurrence of Inactive Debranching Enzyme in Cereals

The interaction of some anthracycline antibiotics (adriamycin, daunomycin, aclacinomycin-A) with bacteriophage ?X174 was investigated. Adriamycin and daunomycin inactivated the infectivity of both free ?X174 phage and naked single-stranded ?X174 DNA without DNA strand scission, but aclacinomycin-A did not show this action. The phage inactivation reaction was reversibly inhibited by Superoxide dismutase, catalase or other oxygen radical scavengers. The inactivation of ?X174 by adriamycin and aclacinomycin-A was stimulated by the addition of Cu²⁺, while the ?X174 inactivation by daunomycin was inhibited by the addition of Cu²⁺. The ?X174 inactivation by adriamycin and aclacinomycin-A in the presence of Cu²⁺ was caused by degradation of DNA, and this inactivation reaction was inhibited irreversibly by oxygen radical scavengers. These results indicate that anthracycline antibiotics bind to ?X174 DNA in the form of free radicals and that during the auto-oxidation of these antibiotics in the presence of Cu²⁺, oxygen radicals were generated to cause the degradation of ?X174 DNA.     

Extra tyrosine in the carbohydrate-binding module of Irpex lacteus Xyn10B enhances its cellulose-binding ability

The xylanase (Xyn10B) that strongly adsorbs on microcrystalline cellulose was isolated from Driselase. The Xyn10B contains a Carbohydrate-binding module family 1 (CBM1) (IrpCBM_Xyn10B) at N-terminus. The canonical essential aromatic residues required for cellulose binding were conserved in IrpCBM_Xyn10B; however, its adsorption ability was markedly higher than that typically observed for the CBM1 of an endoglucanase from Trametes hirsuta (ThCBM_EG1). An analysis of the CBM-GFP fusion proteins revealed that the binding capacity to cellulose (7.8 μmol/g) and distribution coefficient (2.0 L/μmol) of IrpCBM_Xyn10B-GFP were twofold higher than those of ThCBM_EG1-GFP (3.4 μmol/g and 1.2 L/μmol, respectively), used as a reference structure. Besides the canonical aromatic residues (W24-Y50-Y51) of typical CBM1-containing proteins, IrpCBM_Xyn10B had an additional aromatic residue (Y52). The mutation of Y52 to Ser (IrpCBM_Y52S-GFP) reduced these adsorption parameters to 4.4 μmol/g and 1.5 L/μmol, which were similar to those of ThCBM_EG1-GFP. These results indicate that Y52 plays a crucial role in strong cellulose binding.     

Candida albicans β-1,2 mannosyl transferase Bmt3: Preparation and evaluation of a β (1,2), α (1,2)-tetramannosyl fluorescent substrate

We describe for the first time the chemical synthesis of a tetramannoside, containing both α (1 → 2) and β (1 → 2) linkages. Dodecylthio (lauryl) glycosides were prepared from odorless dodecyl thiol and used as donors for the glycosylation steps. This tetramannoside, was coupled to a mantyl group, and revealed to be a perfect substrate of β-mannosyltransferase Bmt3, confirming the proposed specificity and allowing the preparation of a pentamannoside sequence (β Man (1,2) β Man (1,2) α Man (1,2) α Man (1,2) α Man) usable as a novel substrate for further elongation studies.     

裸花紫珠提取物及其主要成分抗氧化活性研究

裸花紫珠是海南一种道地药材,具有消炎止血的功效。裸花紫珠富含黄酮类和苯乙醇苷类化学成分,它们已经被证实是天然抗氧化剂的主要来源之一。为了考察裸花紫珠药材的抗氧化活性,该研究采用DPPH.自由基清除法测定裸花紫珠醇提物、4个不同极性部位(石油醚、乙酸乙酯、正丁醇、水)及其7个主要成分的抗氧化作用。结果表明：裸花紫珠醇提物、醇提物的水部位、正丁醇部位、乙酸乙酯部位和化合物木犀草素、木犀草苷、毛蕊花糖苷具有较强的抗氧化活性,而5-羟基-3,7,3′,4′-四甲氧基黄酮的抗氧化活性则较弱。该研究结果为裸花紫珠的保健功能开发提供了依据。     

New Immunomodulating Polyhydroxypregnane Glycosides from the Roots of Cynanchum otophyllum C.K.Schneid.

Seven new polyhydroxypregnane glycosides, named cynotophyllosides P–V, together with three known analogs were isolated from the roots of Cynanchum otophyllum C.K.Schneid . Their structures were elucidated by a variety of spectroscopic techniques, as well as acid‐catalyzed hydrolysis. All isolates were tested for their immunological activities in vitro against Con A‐ and LPS‐induced proliferation of mice splenocytes. Immunoenhancing (for 1 , 9 ) and immunosuppressive (for 2 ) activities were observed. Furthermore, cynotophylloside R ( 3 ) showed immunomodulatory as it enhanced the proliferation of splenocytes in low concentration and suppressed immune cells in concentration more than 1.0 μg/ml.