Transformation of arctiin to estrogenic and antiestrogenic substances by human intestinal bacteria

After anaerobic incubation of arctiin (1) from the seeds of Arctium lappa with a human fecal suspension, six metabolites were formed, and their structures were identified as (-)-arctigenin (2), (2R,3R)-2-(3',4'-dihydroxybenzyl)-3-(3",4"-dimethoxybenzyl)butyrolactone (3), (2R,3R)-2-(3'-hydroxybenzyl)-3-(3",4"-dimethoxybenzyl)butyrolactone (4), (2R,3R)-2-(3'-hydroxybenzyl)-3-(3"-hydroxy-4"-methoxybenzyl)butyrolactone (5), (2R,3R)-2-(3'-hydroxybenzyl)-3-(3",4"-dihydroxybenzyl)butyrolactone (6), and (-)-enterolactone (7) by various spectroscopic means including two dimensional (2D)-NMR, mass spectrometry, and circular dichroism. A possible metabolic pathway was proposed on the basis of their structures and the time course of the transformation. Enterolactones obtained from the biotransformation of arctiin and secoisolariciresinol diglucoside (SDG, from the seeds of Linum usitatissium) by human intestinal bacteria were proved to be enantiomers, with the (-)-(2R,3R) and (+)-(2S,3S) configurations, respectively. Compound 6 showed the most potent proliferative effect on the growth of MCF-7 human breast cancer cells in culture among 1 and six metabolites, while it showed inhibitory activity on estradiol-mediated proliferation of MCF-7 cells at a concentration of 10 microM. These results indicate that the transformation of 1 by intestinal flora might be essential for the manifestation of the estrogenic and antiestrogenic activity of 1.     

Inclusion of cut and as-grown single-walled carbon nanotubes in the helical superstructure of schizophyllan and curdlan (beta-1,3-glucans)

We have found that single-chain schizophyllan and curdlan (s-SPG and s-curdlan, respectively) can dissolve as-grown and cut single-walled carbon nanotubes (ag-SWNTs and c-SWNTs, respectively) in aqueous solution. The vis-NIR spectra of the composites suggest that c-SWNTs are dissolved as a bundle, whereas ag-SWNTs exist as one or only a few pieces in the tubular hollow constructed by the helical structure inherent to these beta-1,3-glucans. EDX and CLSM measurements and TEM observation established that the distribution map of these polysaccharides overlaps well with the image of SWNTs, indicating that these two components form a composite. Very interestingly, when c-SWNTs were dissolved with the aid of s-SPG or s-curdlan in water, a clear periodical structure with inclined stripes, as detected by AFM, appeared on the fibrous composite surface. Because this periodical structure has never been recognized for the composites with other water-soluble polymers, one can regard that s-SPG or s-curdlan wraps c-SWNTs constructing a helically twined structure. High-resolution TEM observation of an ag-SWNTs/s-SPG composite gave a clearer image in that two s-SPG chains twine one ag-SWNT and the helical motif is right-handed. When this sample was subjected to the AFM measurement, the composite showed the 2-3 nm height. This height implies that one piece of ag-SWNT is included in the s-SPGs helical structure. As a summary, it has been established that beta-1,3-glucans such as s-SPG and s-curdlan not only dissolve SWNTs but also create a novel superstructure on the surface.     

Beta-1,3-glucan polysaccharides as novel one-dimensional hosts for DNA/RNA, conjugated polymers and nanoparticles

Beta-1,3-glucan polysaccharides have triple-stranded helical structures whose sense and pitch are comparable to those of polynucleotides. We recently revealed that the beta-1,3-glucans could interact with certain polynucleotides to form triple-stranded and helical macromolecular complexes consisting of two polysaccharide-strands and one polynucleotide-strand. This unique property of the beta-1,3-glucans has made it possible to utilize these polysaccharides as potential carriers for various functional polynucleotides. In particular, cell-uptake efficiency of the resultant polysaccharide/polynucleotide complexes was remarkably enhanced when functional groups recognized in a biological system were introduced as pendent groups. The beta-1,3-glucans can also interact with various one-dimensional architectures, such as single-walled carbon nanotubes, to produce unique nanocomposites, in which the single-walled carbon nanotubes are entrapped within the helical superstructure of beta-1,3-glucans. Various conductive polymers and gold nanoparticles are also entrapped within the helical superstructure in a similar manner. In addition, diacetylene monomers entrapped within the helical superstructure can be photo-polymerized to afford the corresponding poly(diacetylene)-nanofibers with a uniform diameter. These findings indicate that the beta-1,3-glucans are very attractive and useful materials not only in biotechnology but also in nanotechnology. These unique properties of the beta-1,3-glucans undoubtedly originate from their inherent, very strong helix-forming character which has never been observed for other polysaccharides.     

Synthesis and characterization of polystyrene‐b‐poly (1,2‐isoprene‐ran‐3,4‐isoprene) block copolymers with azobenzene side groups

Polystyrene‐b‐poly(1,2‐isoprene‐ran‐3,4‐isoprene) block copolymers with azobenzene side groups were synthesized by the esterification of azobenzene acid chloride with polystyrene‐b‐hydroxylated poly(1,2‐isoprene‐ran‐3,4‐isopenre) block copolymers for creating new photochromic materials. The resulting block copolymers with azobenzene side groups were characterized for structural, thermal, and morphological properties. IR and NMR spectroscopies confirmed that the polymers obtained had the expected structures. Differential scanning calorimetric measurements by heating runs clearly showed the glass transitions of polystyrene and polyisoprene main chains and two distinct first‐order transitions at temperatures of azobenzene side groups around 48 and 83 °C. The microstructure of these block copolymer films was investigated using both transmission electron microscopy (TEM) and near‐field optical microscopy (NOM). TEM images revealed typical microphase‐separated morphologies such as sphere, cylinder, and lamellar structures. The domain spacing of microphase‐separated cylindrical morphology in the NOM image agreed with that of the TEM results. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2406–2414, 2002     

Enantioselective Synthesis of 3,4‐Dihydropyran‐2‐ones by Domino Michael Addition and Lactonization with New Asymmetric Organocatalysts: Cinchona‐Alkaloid‐Derived Chiral Quaternary Ammonium Phenoxides

Chiral quaternary ammonium phenoxides were readily prepared from commercially available cinchona alkaloids and proved to be useful new asymmetric organocatalysts. Among various chiral quaternary ammonium phenoxides, a cinchonidine‐derived catalyst that bears both a sterically hindered N1‐9‐anthracenylmethyl group and a strongly electron withdrawing 9‐O‐3,5‐bis(trifluoromethyl)benzyl group were found to be highly effective for the Michael addition of ketene silyl acetals (derived from phenyl carboxylates) and α,β‐unsaturated ketones followed by lactonization. Optically active 3,4‐dihydropyran‐2‐one derivatives were obtained in high yields with excellent control of enantio‐ and diastereoselectivity. This catalyst can be handled in air and stored at room temperature in a sealed bottle without decomposition for at least one month.     

Achievement of a 920-MHz high resolution NMR

We have developed a 920-MHz NMR system and performed the proton NMR measurement of H(2)O and ethylbenzene using the superconducting magnet operating at 21.6 T (920 MHz for proton), which is the highest field produced by a superconducting NMR magnet in the persistent mode. From the NMR measurements, it is verified that both homogeneity and stability of the magnet have a specification sufficient for a high resolution NMR.     

Recoil-limited laser cooling of 87Sr atoms near the Fermi temperature

A dynamic magneto-optical trap, which relies on the rapid randomization of population in Zeeman substates, has been demonstrated for fermionic strontium atoms on the 1S0-3P1 intercombination transition. The obtained sample, 1x10(6) atoms at a temperature of 2 microK in the trap, was further Doppler cooled and polarized in a far-off resonant optical lattice to achieve 2 times the Fermi temperature.     

N-tert-Butylbenzenesulfenamide-catalyzed oxidation of alcohols to the corresponding carbonyl compounds with N-chlorosuccinimide

N-tert-Butylbenzenesulfenamide (1)-catalyzed oxidation of various primary and secondary alcohols to the corresponding aldehydes and ketones was efficiently carried out by using N-chlorosuccinimide (NCS) in the coexistence of potassium carbonate and molecular sieves 4 Å at easy-to-control temperatures ranging from 0°C to room temperature. The present catalytic oxidation was performed without giving any damage to the functional groups in alcohols, and was particularly effective in the oxidation of alcohols that formed labile aldehydes because of its mild reaction conditions. Further, selective oxidation of primary hydroxy groups took place in 1-catalyzed oxidation of several diols. Mechanistic investigation suggested that the chlorination of the sulfenamide 1 by NCS led to the formation of a key species, N-tert-butylbenzenesulfinimidoyl chloride (2), which in turn oxidized alcohols in the presence of potassium carbonate to afford carbonyl products by accompanying regeneration of the catalyst 1.