Chemical and Pharmaceutical Bulletin
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  • Volume 65 (2017) Issue 9 Pages 862-868
    Ethereal C–O Bond Cleavage Mediated by Ni(0)-Ate Complex: A DFT Study

    Density functional theory calculations were performed to explore the mechanism of Ni-catalyzed cross-coupling reactions involving organo-lithium and -zinc reagents through ethereal C–O bond cleavage. Based on this work, together with our previous mechanistic study on etheric Kumada–Tamao reaction, we identify and characterize a novel catalytic cycle for cross-coupling mediated by Ni(0)-ate complex.

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    Density functional theory calculations were performed to explore the mechanism of Ni-catalyzed cross-coupling reactions involving organo-lithium and -zinc reagents though ethereal C–O bond cleavage. In comparison with our previous mechanistic study on etheric Kumada–Tamao reaction, it shows that the the Ni(0)-ate complex-mediated reaction pathway is a new and general mechanism for ethereal cross-coupling reactions, which can well explain the experimental findings for several ethereal C–O bond cleavage couplings.  The present work also suggests that the anionic character of organometallic nucleophiles can change oxidative addition mechanisms/pathways, which may provide new reactivity and selectivity.



  • Volume 65 (2017) Issue 9 Pages 848-853
    Effect of the External Lubrication Method for a Rotary Tablet Press on the Adhesion of the Film Coating Layer

    External lubrication is a useful method which reduces the adhesion of powder to punches and dies by spraying lubricants during the tableting process. However, no information is available on whether the tablets prepared using an external lubrication system can be applicable for a film coating process. In this study, we evaluated the adhesion force of the film coating layer to the surface of tablets prepared using an external lubrication method, compared with those prepared using internal lubrication method. We also evaluated wettability, roughness and lubricant distribution state on the tablet surface before film coating, and investigated the relationship between peeling of the film coating layer and these tablet surface properties. Increasing lubrication through the external lubrication method decreased wettability of the tablet surface. However, no change was observed in the adhesion force of the film coating layer. On the other hand, increasing lubrication through the internal lubrication method, decreased both wettability of the tablet surface and the adhesion force of the film coating layer. The magnesium stearate distribution state on the tablet surface was assessed using an X-ray fluorescent analyzer and lubricant agglomerates were observed in the case of the internal lubrication method. However, the lubricant was uniformly dispersed in the external lubrication samples. These results indicate that the distribution state of the lubricant affects the adhesion force of the film coating layer, and external lubrication maintained sufficient lubricity and adhesion force of the film coating layer with a small amount of lubricant.

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    We evaluated the adhesion force of the film coating layer to the surface of tablets prepared using an external lubrication method. Increasing lubrication decreased wettability of the tablet surface. However, no change was observed in the adhesion force of the film coating layer. The magnesium stearate distribution state on the tablet surface was assessed and the lubricant was uniformly dispersed in the external lubrication samples. The distribution state of the lubricant affects the adhesion force of the film coating layer, and external lubrication maintained sufficient lubricity and adhesion force of the film coating layer with a small amount of lubricant.



  • Volume 65 (2017) Issue 9 Pages 840-847
    Four New Lignans and IL-2 Inhibitors from Magnoliae Flos

    Four new lignans, a furofuran lignan medioresinol B (10) and three tetrahydrofuran lignans kobusinol C (16), 7′-methoxy magnostellin A (21), and mangnostellin D (23), along with 19 known lignans, were isolated from the flower buds of Magnolia biondii PAMP. The structures of the isolates were elucidated using spectroscopic analysis, mainly one- and two-dimensional NMR, high resolution-MS, and circular dichroism techniques as well as Mosher’s esterification method. The anti-allergic effects of the isolated compounds were evaluated by analyzing the inhibition of interleukin-2 (IL-2) expression in Jurkat T-cells. Compounds 1114 reduced IL-2 expression in a dose-dependent manner.

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    Four new lignans, a furofuran lignan medioresinol B (10) and three tetrahydrofuran lignans kobusinol C (16), 7'-methoxy magnostellin A (21), and mangnostellin D (23), along with 19 known lignans, were isolated from the flower buds of Magnolia biondii Pamp. The structures of the isolates were elucidated using spectroscopic analysis, mainly one- and two-dimensional NMR, high resolution mass spectrometry, and circular dichroism techniques as well as Mosher’s esterification method. The anti-allergic effects of the isolated compounds were evaluated by analyzing the inhibition of interleukin-2 (IL-2) expression in Jurkat T-cells. Compounds 1114 reduced IL-2 expression in a dose-dependent manner.



  • Volume 65 (2017) Issue 8 Pages 796-800
    7-Hydroxy-3-methyleneisoindolin-1-one as a New ESIPT-Fluorescent Probe to Monitor Aqueous Environments

    A 7-hydroxy derivative of 3-methyleneisoindolin-1-one 1 was synthesized and its properties as a new fluorophore undergoing excited-state intramolecular proton transfer (ESIPT) were investigated. In alcohols and dimethylsulfoxide, 1 exhibited dual emission at ca. 380 and 525−540 nm when excited at ca. 336 nm, which agreed well with the density functional theory (DFT) and time-dependent (TD)-DFT-calculated emission predictions of 1 and its ESIPT tautomer. In aqueous solutions at near neutral pH, 1 exhibited a broad emission band at ca. 497 nm, presumably caused by the overlap of emissions from 1 and the excited state phenolate species of 1. In binary mixtures of H2O and EtOH, the wavelength and intensity of fluorescence maxima were dependent on the dielectric constant of the solvent, suggesting that 1 could be applied as a fluorescent probe to monitor aqueous environments.

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    Fluorophores undergoing excited-state intramolecular proton transfer (ESIPT) exhibit several unique characteristics. In the paper, a range of 7-hydroxy-3-methyleneisoindolin-1-ones is investigated as new ESIPT fluorophores. In fact, dual emission is observed in alcohols and DMSO; ~380 and ~530 nm (exc. = ~336 nm), and a single emission is observed (~500 nm) in EtOH-H2O binary mixtures. Furthermore, the wavelength of fluorescence maxima is dependent on the dielectric constant of the solvent, suggesting their potential utility for monitoring aqueous environments.

  • Volume 65 (2017) Issue 8 Pages 784-795
    Efficient Synthesis of Heterocyclic Flavonoids with Hedgehog Signal Inhibitory Activity

    The hedgehog (Hh) signaling pathway performs important roles in embryonic development and cellular proliferation and differentiation. However, in many cancer cells Hh signaling is aberrantly activated, which has provided a strong impetus for the development of Hh pathway inhibitors. To address this, we synthesized a series of heterocyclic flavonoids and evaluated their Hh signaling inhibitory activity on cancer cell lines using our cell-based assay system. Of the synthetic flavonoids, compounds 4a and g showed good inhibitory activity (IC50 was 16.8 and 21.8 µM, respectively), and were cytotoxic toward human pancreatic (PANC1) and prostate (DU145) cancer cells in which Hh signaling was activated. Compounds 4a and g had moderate selectivity against PANC1 cells. Western blotting analyses revealed that PTCH and GLI1 expression was reduced after treatment with these compounds. Overall, these synthetic flavonoids represent promising new additions to our expanding panel of Hh pathway inhibitors, and with further development these molecules may ultimately be considered for clinical use.

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    The hedgehog (Hh) signaling pathway performs important roles in cellular process, however, in many cancer cells Hh signaling is aberrantly activated, which has provided a strong impetus for the development of Hh pathway inhibitors. In the paper, a series of heterocyclic flavonoids are prepared and evaluate their Hh signaling inhibitory activity. As a result, some of the synthetic flavonoids show good Hh inhibitory activity as well as cytotoxicity toward human cancer cells. Western blotting analyses also reveal that PTCH and GLI1 expression is reduced. 

  • Volume 65 (2017) Issue 8 Pages 726-731
    Melt Adsorption as a Manufacturing Method for Fine Particles of Wax Matrices without Any Agglomerates

    We have focused on melt adsorption as manufacture method of wax matrices to control particles size of granules more easily than melt granulation. The purpose of present study was to investigate the possibility of identifying a hydrophobic material with a low melting point, currently used as a meltable binder of melt granulation, to apply as a novel carrier in melt adsorption. Glyceryl monostearate (GM) and stearic acid (SA) were selected as candidate hydrophobic materials with low melting points. Neusilin US2 (US2), with a particle diameter of around 100 µm was selected as a surface adsorbent, while dibasic calcium phosphate dihydrate (DCPD), was used as a non-adsorbent control to prepare melting granules as a standard for comparison. We prepared granules containing ibuprofen (IBU) by melt adsorption or melt granulation and evaluated the particle size, physical properties and crystallinity of granules. Compared with melt granulation using DCPD, melt adsorption can be performed over a wide range of 14 to 70% for the ratio of molten components. Moreover, the particle size; d50 of obtained granules was 100–200 µm, and these physical properties showed good flowability and roundness. The process of melt adsorption did not affect the crystalline form of IBU. Therefore, the present study has demonstrated for the first time that melt adsorption using a hydrophobic material, GM or SA, has the potential capability to control the particle size of granules and offers the possibility of application as a novel controlled release technique.

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    This paper focuses on melt adsorption as manufacture method of wax matrices to control particles size of granules more easily than melt granulation, and demonstrated for the first time that melt adsorption using a hydrophobic material has the potential capability to control the particle size of granules and offers the possibility of application as a novel controlled release technique.

  • Volume 65 (2017) Issue 7 Pages 605-610
    Potential of Enzymomics Methodologies to Characterize Disease-Related Protein Functions

    Enzymatic functions are often altered during disease onset and progression, and therefore chemical–biological studies, which utilize chemical knowledge to discover novel protein functions, are often employed to find proteins with functions closely related to disease phenotypes. Such studies are known as forward chemical–biological approaches and form part of the emerging field of enzymomics (omics of enzymes). This review provides an overview of methodologies available for discovering and characterizing disease-related alterations of enzymatic functions and prospects for the future.

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    Cellular functions are mediated by a great variety of enzymes, and altered enzymatic functions are often observed during disease onset and progression. Therefore, discovering the novel connection between the functions of enzymes and specified diseases is the key to developing novel diagnostic methods, as well as therapeutic drugs.  In this review, we describe the recently advancing field of chemical biology that aims to discover and characterize disease-related alternation of enzymatic functions, which can be termed as “enzym-omics (omics of enzymes)”.  The review covers several key technologies that can be considered as the representative experimental systems used for this purpose.  

  • Volume 65 (2017) Issue 6 Pages 511-523
    Creation of Novel Cyclization Methods Using sp-Hybridized Carbon Units and Syntheses of Bioactive Compounds

    Some recent results on the development of new and reliable procedures for the construction of diverse ring systems based on the chemistry of sp-hybridized species, especially allene functionality, are described. This review includes: (i) synthesis of the multi-cyclic skeletons by combination of the π-component of allene with suitable other π-components such as alkyne, alkene, or additional allene under Rh-catalyzed conditions; (ii) synthesis of heterocycles as well as carbocycles by reaction of the sp-hybridized center of allene with some nucleophiles in an endo-mode manner; and (iii) total syntheses of natural products and related compounds from the sp-hybridized starting materials.

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    In this review, new and reliable procedures for the construction of diverse ring systems based on the chemistry of sp-hybridized species are described. The synthetic application includes (i) multi-cyclic skeletons by the Rh-catalyzed reaction of allenes with other π-components such as alkyne, alkene, and allene, (ii) hetero- and carbocycles from appropriate allenes and nucleophiles, and (iii) natural products and related compounds.

  • Volume 65 (2017) Issue 5 Pages 409-425
    Palladium(0)-Catalyzed Benzylic C(sp3)–H Functionalization for the Concise Synthesis of Heterocycles and Its Applications

    C–H functionalization reactions involve the activation of otherwise unreactive C–H bonds, and represent atom economical methods for the direct transformation of simple substrates to complex molecules. While transition metal-catalyzed C(sp2)–H functionalization reactions are regularly used in synthesis, C(sp3)–H functionalization is rarely applied to the synthesis of complex natural products because of the difficulties associated with controlling selectivity. With this in mind, we focused on the development of new palladium (Pd)(0)-catalyzed C(sp3)–H functionalization reactions for the synthesis of complex molecules, resulting in several new methods capable of solving these problems. We initially developed a concise synthetic method for the facile construction of oxindoles and spirooxindoles via a Pd-catalyzed benzylic C(sp3)–H functionalization reaction. This method was subsequently extended to the synthesis of various heterocycles, including 2-arylindoles, benzocarbazole, indolocarbazole, indoloquinazolinone, and indoloquinazolinedione, as well as the total synthesis of several pyrrolophenanthridine alkaloids without the need for any protecting groups. This method was also successfully applied to the synthesis of the right-hand fragment of benzohopane from tetrahydro-2H-fluorene, which was constructed by a Pd-catalyzed benzylic C(sp3)–H functionalization. In this review, we provide a detailed discussion of our most recent investigations pertaining to Pd(0)-catalyzed benzylic C(sp3)–H functionalization.

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    This review summarizes author’s recent reports on Pd(0)-catalyzed benzylic C(sp3)-H functionalization for the synthesis of various heterocycles including oxindoles, spirooxindoles, 2-arylindoles, benzocarbazoles, indolocarbazoles, and indoloquinazolinones. The key feature would be a chemoselective C(sp3)-H activation in the oxindole synthesis. The developed method was successfully applied to the total synthesis of several pyrrolophenanthridine alkaloids as well as a synthesis of the right-hand fragment of benzohopane.

  • Volume 65 (2017) Issue 4 Pages 356-358
    Alternative Formation of Red-Shifted Channelrhodopsins: Noncovalent Incorporation with Retinal-Based Enamine-Type Schiff Bases and Mutated Channelopsin

    Red-shifted channelrhodopsins (ChRs) are attractive for optogenetic tools. We developed a new type of red-shifted ChRs that utilized noncovalent incorporation of retinal and 3,4-dehydroretinal-based enamine-type Schiff bases and mutated channelopsin, C1C2-K296G. These ChRs exhibited absorption maxima that were shifted 10–30 nm toward longer wavelengths than that of C1C2-ChR regenerated with all-trans-retinal.

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    In this communication, development of a new type of red-shifted channelrhodopsins (ChRs) is described. Optogenetics is a powerful new technique which allows control of neuronal activity by light, and ChRs are now widely used in optogenetics due to their function of a light-gated cation channel. In neuroscience, ChRs responding to a long-wavelength light are eagerly required, because ChRs now used are maximally sensitive to green and blue light, and does not penetrate tissues. Here developed new type of ChRs model consisted of red-shifted chromophores (retinal-based enamine-type Schiff bases) and mutated channelopsin (C1C2-K296G), in which chromophores were incorporated noncovalently. Thus prepared new ChRs exhibited absorption maxima that were 10-30 nm red-shifted compared with the original C1C2.



  • Volume 65 (2017) Issue 3 Pages 268-275
    Adsorption Capability of Cationic Dyes (Methylene Blue and Crystal Violet) onto Poly-γ-glutamic Acid

    In this study, the adsorption capability of cationic dyes, which were methylene blue and crystal violet, by poly-γ-glutamic acid (PGA) in a single or binary solution system was investigated. The effect of the molecular weight of PGA, initial dye concentration, solution pH, and temperature on the adsorption of dyes was evaluated. The adsorption mechanism of dyes onto PGA was the interaction between –COOH group on the PGA surface and the polarity groups of dyes. These results indicated that PGA is useful for removal of dyes and cationic organic compounds from a single or binary solution system.

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    In this paper, the adsorption capacity of methylene blue (MB) and crystal violet (CV) to poly-γ-glutamic acid (PGA) is described. PGA contained in natto (Japanese traditional fermented food) is a homopolyamide having bonds between α-amino and γ-carboxy groups of D- and L-glutamic acid monomers. The removal rate of MB or CV by PGA was 94.6 to 100% after 120 min. In addition, PGA has a dye adsorption capacity in a binary solution system. The results of this study indicate that PGA is useful for removing dyes from aqueous solutions.



  • Volume 65 (2017) Issue 2 Pages 157-165
    Design of Highly Dispersible PLGA Microparticles in Aqueous Fluid for the Development of Long-Acting Release Injectables

    In this study, we developed highly dispersible polylactic glycolic acid (PLGA) copolymer microparticles (MRPs) in aqueous fluid. A solution containing both dissolved aripiprazole as a model drug and PLGA were spray-dried to make MRPs. The resultant MRPs were further co-processed with water-soluble additives and a surfactant to improve their dispersion behavior. The granules containing MRPs and additives, termed granulated microparticles (G-MRPs) were prepared by a newly established drop freeze-drying technique. The physicochemical properties of MRPs and G-MRPs were evaluated as a long-acting release depot injectable. The MRPs were spherical particles with diameters of approximately 1 to 20 µm and strongly assembled to one another in the aqueous phase, forming large aggregations. In contrast, the G-MRPs were spherical granules with diameters of approximately 200 to 400 µm that displayed a microparticles-in-granule structure in which small MRPs were embedded in the porous matrix inside the granules. When the G-MRPs were placed in water, the porous matrix base was immediately dissolved, and each embedded MRP was individually released, thus inducing monodispersion and significantly improved dispersibility. The excellent dispersibility was attributed to the water-soluble porous network structure mainly composed of D-mannitol and the steric hindrance effects derived from the polymeric molecular chains. These properties may give rise to the excellent passage of PLGA microparticles through needles for use in depot formulation suspensions. A crystalline evaluation of the G-MRPs suggested that the drug and PLGA molecularly interacted and that their thermodynamic stability was improved.

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    In this article, injectable products composed of biocompatible and biodegradable poly-lactic glycolic acid copolymer (PLGA) microparticles are described. In order to improve the dispersibility of MRPs in injection solutions, MRPs were subjected to a secondary processing, i.e., the drop freeze-drying technique. The suspension with MRPs and water-soluble additives were rapidly dripped into liquid nitrogen in the form of droplets. The resultant frozen particles were freeze-dried to prepare spherical granules containing multiple MRPs (Granulated-MRPs). When the G-MRPs were placed in water for injection, the porous matrix base was immediately dissolved, and each embedded MRPs were individually released, thus inducing monodispersion and significantly improved dispersibility. The granular products could be automatically filled into the pre-filled syringes and may give rise to the excellent passage of PLGA MRPs through needles for use in depot injected formulation as a ready-to-use.

  • Volume 65 (2017) Issue 1 Pages 33-35
    Photo-Induced Atom-Transfer Radical Reactions Using Charge–Transfer Complex between Iodine and Tertiary Amine

    In the presence of charge–transfer complexes between iodine and tertiary amines, the aqueous-medium atom-transfer radical reactions proceeded under visible light irradiation without the typical photocatalysts.

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    In this paper, the authors used the charge-transfer complexes between iodine and tertiary amines for the initiation of atom-transfer radical reactions. The visible light irradiation of charge-transfer complex in the ground state gives the excited state complex, in which the single electron transfer from the donor amine to the acceptor iodine proceeds effectively to give an iodine radical.



  • Volume 64 (2016) Issue 12 Pages 1692-1697
    Effect of Nerolidol and/or Levulinic Acid on the Thermotropic Behavior of Lipid Lamellar Structures in the Stratum Corneum

    Permeation enhancers are required to deliver drugs through the skin efficiently and maintain effective blood concentrations. Studies of the barrier function of the stratum corneum using l-menthol, a monocyclic monoterpene widely used in medicines and foods, have revealed an interaction between characteristic intercellular lipid structures in the stratum corneum and permeation enhancers. The variety of permeation enhancers that can be used to contribute to transdermal delivery systems beyond l-menthol is increasing. In this study, we focused on nerolidol and levulinic acid and investigated their influence on stratum corneum lipid structures. Nerolidol, a sesquiterpene, has been reported to enhance the permeation of various drugs. Levulinic acid is reported to enhance the permeability of buprenorphine and is used as a component of the buprenorphine® patch. Synchrotron X-ray diffraction and attenuated total reflectance Fourier transform IR spectroscopy measurements revealed that nerolidol disturbs the rigidly arranged lipid structure and increases lipid fluidity. Levulinic acid had a smaller effect on stratum corneum lipid structures, but did increase lipid fluidity when co-administered with nerolidol or heat. We found that nerolidol has an effect on stratum corneum lipids similar to that of l-menthol, and levulinic acid had an effect similar to that of oleic acid.

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    In this study, the authors focused on two permeation enhancers: nerolidol and levulinic acid to clarify the mechanism of action of permeation enhancers on lipids structures. Synchrotron X-ray diffraction revealed that nerolidol strongly affected the orthorhombic and hexagonal structures, whereas levulinic acid had little effect on the lateral packing structures.



  • Volume 64 (2016) Issue 11 Pages 1533-1538
    Identification of Lung Inflammation-Related Elevation of Acylamino Acid Releasing Enzyme (APEH) Activity Using an Enzymomics Approach

    Disease-associated alterations of enzymatic functions are potentially useful as disease biomarkers, and here we show that an enzymomics (omics of active enzymes) approach, in which enzymatic activities are screened with panels of substrates, can be an effective way to identify such alterations. In the present study, we used a panel of fluorogenic substrates to search for altered enzyme activities in bronchoalveolar lavage fluid (BALF) from a mouse model of lung inflammation. We found that acylamino acid releasing enzyme (APEH) activity was highly elevated, apparently reflecting the increased population of immune cells in the inflamed lung.

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    In this paper, the authors used a panel of fluorogenic substrates to search for altered enzyme activities in bronchoalveolar lavage fluid (BALF) from a mouse model of lung inflammation and found that acylamino acid releasing enzyme (APEH) activity was highly elevated, apparently reflecting the increased population of immune cells in the inflamed lung.



  • Volume 64 (2016) Issue 10 Pages 1431-1437
    Current Understanding of Direct Translocation of Arginine-Rich Cell-Penetrating Peptides and Its Internalization Mechanisms

    Arginine-rich cell-penetrating peptides (CPPs) including Tat, Penetratin and oligoarginine peptides are a series of short peptides that can be efficiently internalized into cells and have been widely used as carriers for intracellular delivery of bioactive molecules. In the early phase of the study, CPPs, as well as their conjugates, were thought to rapidly enter cells by direct penetration through membranes, which was later found to be an experimental artifact that was concluded from observations in fixed cells. Although re-evaluation using living unfixed cells revealed that endocytosis has a major role in internalization of these peptides, there are a number of studies reporting that, even if fixation is avoided, direct translocation across plasma membranes and cytosolic distribution of arginine-rich CPPs are still observed in cells without membrane perturbation. In addition, amphiphilic counteranions such as pyrenebutyrate dramatically accelerate direct translocation of these peptides into cells. These results suggest that there are at least two pathways, i.e., endocytosis and direct translocation, both of which would contribute to cellular internalization of arginine-rich CPPs. In this review, we first introduce the story of fixation artifact, which indeed led to the critical progress in CPP study, and then summarize the current understanding for direct translocation of arginine-rich CPPs. Comprehensive understanding of direct translocation of these peptides and its mechanistic elucidation would provide useful knowledge for developing methodologies that would enable efficient intracellular delivery.

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    In the review, the authors summarize recent reports on direct translocation of arginine-rich cell-penetrating peptides (CPPs) through cell membranes, including counteranion-assisted delivery method, and discuss its mechanism, which would provide insight into highly efficient intracellular delivery.

  • Volume 64 (2016) Issue 9 Pages 1249-1255
    Photocontrol of NO, H2S, and HNO Release in Biological Systems by Using Specific Caged Compounds

    Nitric oxide (NO) is a gas that plays various roles in physiological signal transduction, for example, in vasodilation, neural transmission, and biodefence. Recently, other gaseous signal mediators such as carbon monoxide (CO) and hydrogen sulfide (H2S) have also been found to have important biological activities. Since experimental studies with gaseous mediators are difficult, chemicals that enable controlled release of these gases are indispensable. We have developed a range of photocontrollable releasers that generate NO, H2S, and related species with fine spatiotemporal control, and we have also employed these caged compounds in various applications. This paper briefly reviews our work on photocontrollable NO, H2S, and HNO releasers, and presents some typical applications illustrating the suitability of our compounds for controlled release of these biologically active species in cellular and tissue systems. These compounds also appear to have potential for future therapeutic applications.

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    This review summarizes the authors’ recent work on photocontrolable releases, or caged compounds, which can release specific biological mediators such as NO, HNO, and H2S, upon photoirradiation, and a wide range of colors (wavelengths), from ultraviolet to near infrared, are available depending on the properties of the compounds. These photocontrollable compounds realized the spatiotemporal control of the release, and the manipulation of biological responses specific for the mediators. One of our photocontrollable NO releasers with the near infrared two photon excitation succeeded to control vasodilation in the anesthetized mouse brain with spatiotemporal resolution, and the ex vivo rat aorta relaxation was also achieved with another controllable NO releaser by the visible light irradiation.

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