Tetsuya Ogura

Flavonols from Heterotheca inuloides: tyrosinase inhibitory activity and structural criteria.

Tyrosinase inhibitory activity of flavonols, galangin, kaempferol and quercetin, was found to come from their ability to chelate copper in the enzyme. In contrast, the corresponding flavones, chrysin. apigenin and luteolin, did not chelate copper in the enzyme. The chelation mechanism seems to be specific to flavonols as long as the 3-hydroxyl group is free. Interestingly, flavonols affect the enzyme activity in different ways. For example, quercetin behaves as a cofactor and does not inhibit monophenolase activity. On the other hand, galangin inhibits monophenolase activity and does not act as a cofactor. Kaempferol neither acts as a cofactor nor inhibits monophenolase activity. However, these three flavonols are common to inhibit diphenolase activity by chelating copper in the enzyme.

A catalytic application of Cu2O and CuO films deposited over fiberglass

Abstract With the purpose of utilizing copper oxides over fiberglass as a novel catalyst material in oxidation reactions, we have used the chemical vapor deposition of 2,4-pentanedionate copper(II) as a precursor and fiberglass as substrate. The deposition of copper oxides was achieved in a horizontal-flow reactor using O2 as carrier-reactant gas at several deposition temperatures. Copper species deposited on fiberglass were characterized by X-ray diffraction (XRD), UV–visible spectrophotometry (UV–VIs) and scanning electronic microscopy (SEM) techniques. The fiberglass coated with copper oxides showed a catalytic activity for the oxidation of ethanol into a stream of air at different temperatures in a pulse microreactor.

Irritant contact dermatitis caused by needle-like calcium oxalate crystals, raphides, in Agave tequilana among workers in tequila distilleries and agave plantations

It was found that needle‐like calcium oxalate crystals, raphides, are found abundantly in all tissues of Agave tequilana plants; thus, 1 droplet (0.03 ml) of juice pressed from leaves contains 100–150 crystals, 30–500 μm in length, sharpened at both ends. In tequila distilleries, 5/6 of the workers who handle the agave stems have experienced the characteristic irritation. In contrast, only 1/3 of workers in agave plantations who harvest agave plants, complain of the irritation. It is confirmed that all the irritation suffered in both distilleries and plantations takes place at bodily locations where the plants come into contact with the workers skin in the course of their work.

Formation of copper oxychloride and reactive oxygen species as causes of uterine injury during copper oxidation of Cu-IUD

The lining of the uterus and cervix might be injured by a variety of oxidation products of Cu in a Cu-IUD, including cuprous ions, dissolved and precipitated cupric ions, and reactive oxygen species such as superoxide radicals, hydrogen peroxide, and hydroxyl radicals. In this study, the human amnious WISH cell line was employed as a model of uterine cells in the presence of copper. The cell viability was decreased by elemental copper, which was alleviated up to 70% by the addition of catalase. The addition of copper oxychloride caused cell death in a dose-dependent manner. Hydroxyl radicals in the presence of copper were determined by the formation of malondialdehyde. Soluble cuprous chloride complexes are formed in the uterus by slowly entering oxygen. The complexes are partly oxidized to insoluble copper oxychloride. which damages the endometrium. Unoxidized cuprous ions migrate to the oxygen-rich cervix and are oxidized to copper oxychloride, causing cervix damage.

Inhibition of lipid peroxidation by sesquiterpenoid in Heterotheca inuloides

A sesquiterpenoid, 7‐hydroxy‐3,4‐dihydrocadalin, isolated from a Mexican medicinal plant Heterotheca inuloides was evaluated as an antioxidant.

Tyrosinase inhibitory flavonoids fromheterotheca inuloides and their structural functions

Abstract By bioassay-guided fractionations, quercetin was isolated as the principal tyrosinase inhibitor from the dried flowers of Heterotheca inuloides Cass (Compositae). This flavonol inhibited the oxidation of L-3,4-dihydroxyphenylalanine (L-DOPA) by mushroom tyrosinase (EC 1.14.18.1) with an ID 50 of 22 μg/ml (0.07 mM). Interestingly, quercetin 3-β-glucoside did not inhibit this oxidation up to 1 mg/ml. Kinetic study have found quercetin to be a characteristic competitive inhibitor for the L-DOPA oxidation by the mushroom tyrosinase. Based on the above findings, several related flavonoids were also examined for comparison.

Complex formations of silver(I) trifluoroacetate and trifluoromethanesulfonate with benzene and cyclohexene

Abstract An apparatus for measurements of equilibrium ligand vapor pressure has been applied in order to determine the stoichiometry of benzene and cyclohexene complexes of silver(I) trifluoroacetate (AgCF 3 CO 2 ) and silver(I) trifluoromethanesulfonate (silver(I) triflate, AgCF 3 SO 3 ) in the solid state. It has been found that the equilibrium leads the formation of such complexes as: (AgCF 3 CO 2 ) 2 (C 6 H 6 ), (AgCF 3 CO 2 ) 2 (C 6 H 10 ), (AgCF 3 CO 2 ) 2 (C 6 H 10 ) 3 , (AgCF 3 SO 3 ) 2 (C 6 H 6 ), (AgCF 3 SO 3 )(C 6 H 6 ), (AgCF 3 SO 3 )(C 6 H 10 ) and (AgCF 3 SO 3 )(C 6 H 10 ) 2 . The temperature dependence of the gas-solid equilibrium ligand pressure has also been examined for these complexes, and the enthalpy and entropy changes according to the following complex dissociation reactions were estimated: (AgCF 3 CO 2 )L m (s) ⇄ AgCF 3 CO 2 (s)+mL (g): and (AgCF 3 SO 3 )L n (s) ⇄ AgCF 3 SO 3 (s)+nL (g), where Ls are benzene and cyclohexene. On the basis of the thermodynamic data obtained, the effects of the counter anion as well as the ligand on the complex stability are discussed.

Cultivable endophytic bacteria from leaf bases of Agave tequilana and their role as plant growth promoters

Agave tequilana Weber var. ‘Azul’ is grown for the production of tequila, inulin and syrup. Diverse bacteria inhabit plant tissues and play a crucial role for plant health and growth. In this study culturable endophytic bacteria were extracted from leaf bases of 100 healthy Agave tequilana plants. In plant tissue bacteria occurred at mean population densities of 3 million CFU/g of fresh plant tissue. Three hundred endophytic strains were isolated and 16s rDNA sequences grouped the bacteria into eight different taxa that shared high homology with other known sequences. Bacterial endophytes were identified as Acinectobacter sp., A. baumanii, A. bereziniae, Cronobacter sakazakii, Enterobacter hormaechei, Bacillus sp. Klebsiella oxytoca, Pseudomonas sp., Enterococcus casseliflavus, Leuconostoc mesenteroides subsp. mesenteroides and Gluconobacter oxydans. Isolates were confirmed to be plant growth promoting bacteria (PGPB) by their capacities for nitrogen fixation, auxin production, phosphate solubilization, or antagonism against Fusarium oxysporum AC132. E. casseliflavus JM47 and K. oxytoca JM26 secreted the highest concentrations of IAA. The endophyte Acinectobacter sp. JM58 exhibited the maximum values for nitrogen fixation and phosphate solubilization index (PSI). Inhibition of fungi was found in Pseudomonas sp. JM9p and K. oxytoca JM26. Bacterial endophytes show promise for use as bio-inoculants for agave cultivation. Use of endophytes to enhance cultivation of agave may be particularly important for plants produced by micropropagation techniques, where native endophytes may have been lost.

Inhibition mode of soybean lipoxygenase-1 by quercetin.

Quercetin noncompetitively inhibited the peroxidation of linoleic acid catalyzed by soybean lipoxygenase‐1 (EC 1.13.11.12, Type 1) with an IC50 value of 4.8 μM (1.45 μg/ml). This inhibition is considered to proceed in sequential order, by initially reducing the ferric form of the enzyme to an inactive ferrous form and then, by chelating the iron of the active site of the enzyme. In the pseudoperoxidase assay, quercetin was slowly oxidized by hydroperoxides to a rather stable intermediate, 2‐(3,4‐dihydroxybenzoyl)‐2,4,6‐trihydroxybenzofuran‐3(2H)‐one, and this oxidized intermediate still inhibited the enzymatic oxidation, probably as a chelator. Rutin and kaempferol also exhibited lipoxygenase‐1 inhibitory activity, but to a much lesser extent than quercetin.

A plant growth inhibitory sesquiterpenoid from Heterotheca inuloides

Abstract A new sesquiterpenoid, inuloidin, isolated from the dried flower of Heterotheca inuloides has been characterized as 2,7-dihydroxy-β-calacoren or 7-hydroxy-5,6,7,8-tetrahydro-3-methyl-8-methylene-5-(1-methylethyl)-2-naphthalenol by means of spectroscopic method. It exhibited plant growth inhibitory activity in lettuce seedling assay.