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.     

An expedient synthesis of ellipticine via Suzuki-Miyaura coupling

A simple and efficient total synthesis of ellipticine was developed via the Suzuki-Miyaura coupling of sterically sensitive 2-hydroxybenzeneboronic acid with a multifunctional aryl halide using Pd(OAc)₂ as a catalyst and Cu(OAc)₂·H₂O as an additive in DMSO/H₂O as a key step followed by double N-arylation and cyclization.     

Enantioselective desymmetrization of meso-N-(heteroarenesulfonyl)aziridines with TMSN3 catalyzed by chiral Lewis acids

A catalytic enantioselective desymmetrization of meso-N-(heteroarenesulfonyl)aziridines with TMSN₃ using chiral Lewis acids afforded products with high enantioselectivity. As proof of the utility of this procedure, the precursor of selective κ-opioid agonist (1S,2S)-(−)-U-50,488 was synthesized.     

Thermo-mechanical properties of microfibrillated cellulose-reinforced partially crystallized PLA composites

Polylactic acid (PLA) in a crystallized state has mechanical properties at high temperatures superior to PLA in an amorphous state. However, a long annealing time is required to fully crystallize PLA. In this study, microfibrillated cellulose (MFC)-reinforced partially crystallized PLA composites were produced, with the goal of reducing the time required to fabricate PLA parts. A series of PLA/MFC composites at a fiber content of 10 wt% from degree of crystallinity (Xc) 0 to 43% was obtained by annealing at 80 °C. Although the annealing time required to obtain a composite (Xc: 17%) was only around one-seventh of the 20 min needed to fully crystallize neat PLA (Xc: 41%), both materials had comparable rigidity above the glass transition temperature (T _g) and creep deformation at around T _g. These results showed that partially crystallized PLA/MFC composite can replace fully crystallized neat PLA.     

Mechanistic discussion of cationic crosslinking copolymerizations of 1,2‐epoxycyclohexane with diepoxide crosslinkers accompanied by intramolecular and intermolecular chain transfer reactions

Our previous mechanistic discussion of the free‐radical crosslinking monoallyl/diallyl copolymerizations was extended to the cationic crosslinking monoepoxide/diepoxide copolymerizations, typically including 1,2‐epoxycyclohexane (ECH) as a monoepoxide and bis[3,4‐epoxycyclohexylmethyl] adipate (BECHMA) as a diepoxide crosslinker. In the cationic polymerization, oligomer is usually obtained because of the occurrence of characteristic chain‐forming reactions. Therefore, cationic crosslinking monoepoxide/diepoxide copolymerizations could be in the category of the network formation through free‐radical crosslinking monoallyl/diallyl copolymerizations. Thus, the gelation behavior was discussed by comparing the actual gel points with the theoretical ones; the greatly delayed gelation from theory was observed. Then, the resulting network polymer precursors (NPPs) were characterized by SEC‐MALLS‐viscometry to clarify the cationic crosslinking ECH/BECHMA copolymerization mechanism. Notably, the correlation lines of molecular weight versus elution volume were specific for the NPPs obtained at a high conversion close to the gel point as compared with those obtained by the free‐radical crosslinking monoallyl/diallyl copolymerization. This may be ascribed to the occurrence of intramolecular and intermolecular chain transfer reactions characteristic of cationic polymerization; the chain transfer reactions involve the intramolecular and intermolecular nucleophilic attack of ether oxygen or terminal hydroxyl oxygen in the NPPs to a terminal growing cation that leads to the formation of not only the loop‐ but also the crosslink‐structures containing NPPs, providing fragile ultrahigh‐molecular‐weight NPP in the SEC columns. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Competitive Assay for Theophylline Based on an Abasic Site‐Containing DNA Duplex Aptamer and a Fluorescent Ligand

A fluorescence assay for theophylline, one of the common drugs for acute and chronic asthmatic conditions, has been developed based on an abasic site‐containing DNA duplex aptamer (AP aptamer) in combination with an abasic site‐binding fluorescent ligand, riboflavin. The assay is based on the competitive binding of theophylline and riboflavin at the abasic (AP) site of the AP aptamer. In the absence of theophylline, riboflavin binds to the receptor nucleotide opposite the AP site, which leads to fluorescence quenching of the riboflavin. Upon addition of theophylline, competitive binding occurs between theophylline and riboflavin, which results in an effective fluorescence restoration due to release of riboflavin from the AP site. From an examination of the optimization of the AP aptamers, the complex of riboflavin with a 23‐mer AP aptamer (5′‐TCT GCG TCC AGX GCA ACG CAC AC‐3′/5′‐GTG TGC GTT GCC CTG GAC GCA GA‐3′; X : the AP site (Spacer C3, a propylene residue)) possessing cytosine as a receptor nucleotide was found to show a selective and effective fluorescence response to theophylline; the limit of detection for theophylline was 1.1 μM . Furthermore, fluorescence detection of theophylline was successfully demonstrated with high selectivity in serum samples by using the optimized AP aptamer and riboflavin.     

Me‐BIPAM for the Synthesis of Optically Active 3‐Aryl‐3‐hydroxy‐2‐oxindoles by Ruthenium‐catalyzed Addition of Arylboronic Acids to Isatins

A chiral O‐linked C₂‐symmetric bidentate phosphoramidite (Me‐BIPAM) was found to be efficient for the ruthenium‐catalyzed addition of arylboronic acids to isatins. Asymmetric synthesis of 3‐aryl‐3‐hydroxy‐2‐oxindoles by 1,2‐addition of arylboronic acids to isatins was carried out in the presence of [RuCl₂(PPh₃)₃]/(R,R)‐Me‐BIPAM and KF, resulting in an enantioselectivity as high as 90 % ee. It was found that the reaction with N‐protected isatins proceeds with high yields and good enantioselectivities. The best protective groups on the nitrogen atom were different depending on the substituents on the aromatic ring. The use of a N‐benzyl group resulted in excellent enantioselectivities in many substrates compared with other groups.     

Proposal of sampling process for collecting human sweat and determination of caffeine concentration in it by using GC/MS

Caffeine concentration in human sweat was estimated by measuring separately the amounts of water and caffeine. After washing a finger with tap water for 15 s and waiting 2 min for drying, 70 microL aqueous ethanol solution in a small vial (0.6 mL) was used to sample for several minutes. Then 3 microL of the aliquot was used for GC/MS analysis of caffeine. As a first-order relationship between the sweat amount secreted on the left and right hands was obtained (correlation factor 0.848), the amount of sweat secretion during sampling on one hand was estimated by the value obtained on the other hand. This new indirect evaluation was used for the estimation of the amount of sweat secreted during sampling. Typical variations of caffeine concentration in sweat were demonstrated. Thirty minutes after the intake of caffeine, it was secreted in sweat, and the secretion had continued for more than 4 h.