Medicinal flowers. XXXIII. Anti-hyperlipidemic and anti-hyperglycemic effects of chakasaponins I-III and structure of chakasaponin IV from flower buds of Chinese tea plant (Camellia sinensis)

Effects of principal saponins, chakasaponins I-III, from the flower buds of Camellia sinensis cultivated in Fujian province, China on plasma triglyceride (TG) and glucose levels in olive oil or sucrose-loaded mice were examined. Chakasaponins I-III at 50 and 100 mg/kg significantly inhibited increases in plasma TG and glucose levels. Furthermore, they prevented gastric emptying, suggesting that the former inhibitory effect is partly dependent on the inhibition of gastric emptying. In addition, the chemical structure of a new acylated oleanane-type triterpene oligoglycoside, chakasaponin IV, was elucidated on the basis of chemical and physicochemical evidence.     

Structure elucidation of a novel analog of sildenafil detected as an adulterant in a dietary supplement using LC-UV and LC/MS

A sildenafil-related compound was detected in a dietary supplement marketed as an aphrodisiac. The compound was detected during analysis of the dietary supplement using LC-UV and LC/electrospray ionization-MS. The structure of the compound was established using high resolution MS, NMR spectrometry, and X-ray crystal structure analysis. The compound was identified as 5-(5-((3,5-dimethylpiperazin-1-yl)sulfonyl)-2-ethoxyphenyl)-l-methyl-7-((1-methyl-4-nitro-1H-imidazol-5-yl)thio)-3-propyl-1H-pyrazolo[4,3-d] pyrimidine. Based on this structure, the compound was named nitroprodenafil. The dietary supplement was found to contain 90 mg nitroprodenafil/capsule. This article describes the structural characterization of a new sildenafil-related compound. The compound was detected during analysis of a dietary supplement using LC-UV and LC/electrospray ionization (ESI)-MS. The structure was established using high resolution MS (HRMS), NMR spectrometry, and X-ray crystal structure analysis. The structures of methisosildenafil, thiomethisosildenafil, and this new analog, named nitroprodenafil (21), are shown in Figure 1. In the Demizu et al. report, the compound is named mutaprodenafil instead ofnitroprodenafil. Considering the naming right, the authors of this paper think the use of mutaprodenafil is appropriate as the compound name, although nitroprodenafil is used.     

Secure key distribution using correlated randomness in lasers driven by common random light

We propose a secure key distribution scheme based on correlated physical randomness in remote optical scramblers driven by common random light. The security of the scheme depends on the practical difficulty of completely observing random optical phenomena. We describe a particular realization using the synchronization of semiconductor lasers injected with common light of randomly varying phase. We experimentally demonstrate the feasibility of the scheme over a distance of 120 km.     

Effect of expiratory flow rate on the acoustic characteristics of sibilant /s/

Sibilant /s/, which is an unvoiced sound, is believed to be produced by a jet of air through a sibilant groove toward the sharp edges of the teeth. We investigated what effects the expiratory flow rate had on the acoustic characteristics of sibilant /s/ in the present study. A large eddy simulation was implemented to investigate the flow in an oral cavity model that simplified the important anatomical features of the oral cavity when sibilant /s/ was pronounced. The results illustrated that an increase in the expiratory flow rate caused turbulence to develop in the separated flow from the edge of the obstacle wall which mimics a tooth. The increase in turbulent intensity induced a dramatic elevation in Lamb-vector divergence in the flow-separation region, which was regarded as a sound source of sibilant /s/. The total power of the sound source which was located near the obstacle edge of the obstacle wall at smaller flow rates, extended downstream in the flow separation as the expiratory flow rate increased through which turbulence developed. These results demonstrated that the expiratory flow rate had a significant influence on the acoustic characteristics of sibilant /s/ particularly when the flow rate increased to cause turbulence.     

Synthesis and properties of poly(carbonate‐urethane) consisting of alternating carbonate and urethane moieties

Poly(carbonate‐urethane) consisting of alternating carbonate and urethane moieties (poly(HC‐MDI)) was prepared by polyaddition of 4,4′‐diphenylmethane diisocyanate (MDI) and a monocarbonate diol bis(3‐hydroxypropyl)carbonate (HC), prepared by hydrolysis of a six‐membered spiroorthocarbonate 1,5,7,11‐tetraoxa‐spiro[5.5]undecane. The polyaddition proceeds without concomitant side reactions including carbonate exchange reaction and affords the desired poly(carbonate‐urethane). The hydrolysis and thermal behaviors of poly(HC‐MDI) were compared with those of the analogous polyurethane carrying no carbonate structure (poly(ND‐MDI)) prepared from MDI and 1,9‐nonanediol (ND). Although the glass transition behaviors are almost identical, poly(HC‐MDI) is less crystalline than poly(ND‐MDI). Poly(HC‐MDI) is more susceptible to hydrolysis than poly(ND‐MDI) probably due to the higher polarity and the lower crystallinity. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2802–2808, 2006     

Design of Fe-MOF-bpdc deposited with cobalt oxide (CoOx) nanoparticles for enhanced visible-light-promoted water oxidation reaction

Research on Chemical Intermediates - This work spotlights the facile method to deposit cobalt oxide (CoOx) nanoparticles as a cocatalyst on Fe-MOF-bpdc to enhance its photocatalytic activity for...     

Electrochemical evaluation of alternating duplex-triplex conversion effect on the anthraquinone-photoinjected hole transport through DNA duplex immobilized on a gold electrode

Amperometry was employed to characterize the anthraquinone (AQ)-photoinjected hole transport through a 20-mer oligodeoxynucleotide (ODN) duplex, as immobilized on the surface of a gold electrode, and its triplex forms converted by association with several third oligopyrimidine (OPD) short strands. While the cathodic photocurrent was observed upon irradiation at 365 nm of the AQ photosensitizer linked to the end of DNA duplex, a marked lowering of the current density was identified to occur by the triplex formation of a duplex with a given third OPD short strand. The photocurrent through the DNA duplex showed a reversible fall-rise response concomitant with alternating association-dissociation cycle of the OPD short-strand, as regulated by temperature change around the corresponding melting temperature of the DNA triplex. Both the switched photoirradiation and the thermally alternating duplex-triplex conversion could provide tools of regulating the DNA hole transport.     

Isolation and Structure Determination of a Missing Endohedral Fullerene La@C70 through In Situ Trifluoromethylation

D_5h‐symmetric fullerene C₇₀ (D_5h‐C₇₀) is one of the most abundant members of the fullerene family. One longstanding mystery in the field of fullerene chemistry is whether D_5h‐C₇₀ is capable of accommodating a rare‐earth metal atom to form an endohedral metallofullerene M@D_5h‐C₇₀, which would be expected to show novel electronic properties. The molecular structure of La@C₇₀ remains unresolved since its discovery three decades ago because of its extremely high instability under ambient conditions and insolubility in organic solvents. Herein, we report the single‐crystal X‐ray structure of La@C₇₀(CF₃)₃, which was obtained through in situ exohedral functionalization by means of trifluoromethylation. The X‐ray crystallographic study reveals that La@C₇₀(CF₃)₃ is the first example of an endohedral rare‐earth fullerene based on D_5h‐C₇₀. The dramatically enhanced stability of La@C₇₀(CF₃)₃ compared to La@C₇₀ can be ascribed to trifluoromethylation‐induced bandgap enlargement.     

Physicochemical mechanism for the enhanced ability of lipid membrane penetration of polyarginine

Arginine-rich, cell-penetrating peptides (e.g., Tat-peptide, penetratin, and polyarginine) are used to carry therapeutic molecules such as oligonucleotides, DNA, peptides, and proteins across cell membranes. Two types of processes are being considered to cross the cell membranes: one is an endocytic pathway, and another is an energy-independent, nonendocytic pathway. However, the latter is still not known in detail. Here, we studied the effects of the chain length of polyarginine on its interaction with an anionic phospholipid large unilamellar vesicle (LUV) or a giant vesicle using poly-l-arginine composed of 69 (PLA69), 293 (PLA293), or 554 (PLA554) arginine residues, together with octaarginine (R8). ζ-potential measurements confirmed that polyarginine binds to LUV via electrostatic interactions. Circular dichroism analysis demonstrated that the transition from the random coil to the α-helix structure upon binding to LUV occurred for PLA293 and PLA554, whereas no structural change was observed for PLA69 and R8. Fluorescence studies using membrane probes revealed that the binding of polyarginine to LUV affects the hydration and packing of the membrane interface region, in which the degree of membrane insertion is greater for the longer polyarginine. Isothermal titration calorimetry measurements demonstrated that although the binding affinity (i.e., the Gibbs free energy of binding) per arginine residue is similar among all polyarginines the contribution of enthalpy to the energetics of binding of polyarginine increases with increasing polymer chain length. In addition, confocal laser scanning microscopy showed that all polyarginines penetrate across giant vesicle membranes, and the order of the amount of membrane penetration is R8 ≈ PLA69 < PLA293 ≈ PLA554. These results suggest that the formation of α-helical structure upon lipid binding drives the insertion of polyarginine into the membrane interior, which appears to enhance the membrane penetration of polyarginine.