Characteristic metabolites of Hypericum plants : their chemical structures and biological activities

Plants belonging to the genus Hypericum (Hypericaceae) are recognized as an abundant source of natural products with interesting chemical structures and intriguing biological activities. In the course of our continuing study on constituents of Hypericum plants, aiming at searching natural product-based lead compounds for therapeutic agents, we have isolated more than 100 new characteristic metabolites classified as prenylated acylphloroglucinols, meroterpenes, ketides, dibenzo-1,4-dioxane derivatives, and xanthones including prenylated xanthones, phenylxanthones, and xanthonolignoids from 11 Hypericum plants and one Triadenum plant collected in Japan, China, and Uzbekistan or cultivated in Japan. This review summarizes their chemical structures and biological activities

Phytochemical studies on traditional herbal medicines based on the ethnopharmacological information obtained by field studies

Traditional herbal medicines, which have been used in the matured traditional medical systems as well as those have been used in ethnic medical systems, are invaluable resources of drug seeds. Ethnobotanical and ethnopharmacological survey may provide useful information of these herbal medicines, which are valuable for searching new bioactive molecules. From this viewpoint, we have been performing the ethnobotanical and ethnopharmacological field studies in Yunnan Province and Guangxi Zhuang Autonomous Region, China, and Mongolia. Phytochemical studies on traditional herbal medicines were performed based on the information obtained by our ethnobotanical survey. Herbal medicines used in Uzbekistan and Bangladesh were also investigated on the basis of the ethnopharmacological information obtained from collaborative researchers in the respective regions. Some studies were carried out for searching active substance(s) based on bioassay-guided fractionation and isolation. Over 150 new molecules were isolated in these studies, and their various biological activities were also demonstrated. This review summarizes the results of phytochemical studies of those traditional herbal medicines as well as biological activities of the isolated molecules

Frustrated element-blocks: A new platform for constructing unique stimuli-responsive luminescent materials

Element-blocks, the minimum heteroatom-containing functional units, are versatile building blocks for constructing functional polymers. In this focus review, we explain the new concept of developing stimuli-responsive luminochromic materials based on frustrated element-blocks. Herein, we termed “frustrated” element-blocks as those that show a relatively larger degree of structural relaxation in the excited state but are structurally restricted. As a result, frustrated element-blocks can have unique stimuli-responsive luminochromic behaviors. As a representative example, the stimuli-responsive properties of frustrated boron clusters are initially illustrated, and a series of their luminochromic properties, such as mechano- and thermochromism, are described. Next, we designed fused complexes for suppressing intramolecular motion to obtain frustrated boron complexes that display constant emission in both the solution phase and solid-state to produce mechanochromic luminescent materials. Finally, generating the frustrated state by polymerization is explained. These polymers display unique luminochromic behaviors, such as thermochromism in solution, mechanochromism in the solid-state and vapochromism. Finally, the stimuli-responsive luminochromic behaviors of frustrated element-block-containing polymers and their mechanisms are illustrated, mainly by examples from our recent works

High HOMO levels and narrow energy band gaps of dithienogalloles

We synthesized dithieno[3, 2-b:2′, 3′-d]galloles containing four-coordinated gallium atoms. It was found that dithienogalloles had high stability to air and moisture and showed narrower energy-band gaps than dithienosiloles which are commodity materials in organic opto and/or electronic devices. In addition, relatively-higher HOMO levels were observed from dithienogalloles than those of other dithienoheteroles from electrochemical measurements. We experimentally and theoretically demonstrated the electron-donating properties and resonance effects of gallium atoms of dithienogalloles

Tuning of Sensitivity in Thermochromic Luminescence by Regulating Molecular Rotation Based on Triphenylamine-Substituted o-Carboranes

This study shows tuning of sensitivity in thermochromic luminescence from triphenylamine‐substituted o‐carboranes by regulating rotation barriers with a substituent effect. A series of o‐carborane dyads with various numbers of methyl substituents were prepared, and their optical properties were compared. Initially, significant dual‐emission properties consistent of the locally excited (LE) state and the induced charge transfer (ICT) state were observed from the solid samples of all dyads. In particular, diverse responses were obtained by cooling from the dyads. The pristine and mono‐substituted dyads presented thermally independent emission during temperature changes, whereas the detected thermochromic luminescence with drastic color change from red to blue originated from the alteration of intensity ratios between LE and CT emission bands. From mechanistic studies (experimental and theoretical), it was clearly shown that the difference in the rotation barrier of the o‐carborane unit caused by the substituent effect should play a key role in variable sensitivity in luminescent chromic behaviors in temperature change

On Local Symmetric Order Parameters of Vortex Lattice States

This paper gives a new refined definition of local symmetric order parameters (OPs)(s-wave, d-wave and p-wave order parameters) of vortex lattice states for singlet superconductivity. s-wave, d-wave and p-wave OPs at a site (m,n) are defined as A, B and E representations of the four fold rotation C_4 at the site (m,n) of nearest neighbor OPs etc. The new OPs have a well defined nature such that an OP(e.g. d-wave) at the site obtained under translation by a lattice vector (of the vortex lattice) from a site (m,n) is expressed by the corresponding OP (e.g. d-wave) at the site (m,n) times a phase factor. The winding numbers of s-wave and d-wave OPs are given.Comment: RevTeX v3.1, 5 pages with 3 figures, uses epsf.sty. to appear in Prog. Theor. Phys. Vol.101 No.3. (1999

Light-driven artificial enzymes for selective oxidation of guanosine triphosphate using water-soluble POSS network polymers.

Accepted 25 Jun 2014.The light-driven artificial enzymes were constructed to realize unnatural reactions concerning bio-significant molecules. In this manuscript, the guanosine triphosphate (GTP)-selective oxidation is reported using the network polymers composed of polyhedral oligomeric silsesquioxane (POSS). We synthesized the water-soluble POSS network polymer containing the naphthyridine ligands to capture GTP inside the networks and the ruthenium complexes to oxidize the captured GTP under light irradiation. Initially, the binding affinities of the guanosine nucleosides to the naphthyridine ligand inside the POSS network polymer were evaluated from the emission quenching experiments. Accordingly, it was observed that the naphthyridine ligand can form the stable complex only with GTP (K(a) = 5.5 × 10(6) M(-1)). These results indicate that only GTP can be captured by the network polymer. Next, the photo-catalytic activity of the ruthenium complex-modified POSS network polymer was investigated. Finally, it was revealed that the network polymer can decompose GTP efficiently under light irradiation. This is the first example, to the best of our knowledge, to offer not only the GTP-selective host polymers but also the light-driven artificial enzyme for GTP oxidation

Enhancing Light-Absorption and Luminescent Properties of Non-Emissive 1,3,4,6,9b-Pentaazaphenalene through Perturbation of Forbidden Electronic Transition by Boron Complexation

We report an improvement of optical properties of the non‐emissive molecule through shuffling the molecular orbitals by boron complexation. The 1, 3, 4, 6, 9b‐pentaazaphenelene (5AP) derivative having a 2‐(dimesitylboryl)phenyl group was synthesized through a substitution reaction from a 2‐bromophenyl compound. The formation of the B−N dative bond was confirmed by ¹¹B{¹H} NMR spectroscopy and a single‐crystal X‐ray structure analysis. Most of the conventional 5AP derivatives hardly showed emission despite their planar and rigid molecular structures. The previous reports on 5AP derivatives ascribed the non‐luminescent behavior to the forbidden transition between frontier orbitals. On the other hand, the 5AP‐based boron complex in this work showed enhanced light absorption and luminescence from the HOMO−LUMO transition. Theoretical calculations suggested that the boron complexation should play a critical role in perturbing the forbidden character of the HOMO−LUMO transition. Because the nitrogen atom on the 5AP moiety formed the Lewis acid−base pair with the boron atom, the energy level of the HOMO of 5AP was downshifted. The character of the HOMO−LUMO transition of the boron complex was changed to afford the improved optical properties of the boron complex