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Featured researches published by Tetsuya Konishi.


Journal of Medicinal Food | 2001

Antioxidant Activity of Anthocyanin Extract from Purple Black Rice

Haruyo Ichikawa; Takashi Ichiyanagi; Bing Xu; Yoichi Yoshii; Masaharu Nakajima; Tetsuya Konishi

Antioxidant activity was studied for anthocyanins extracted from purple black rice (PBR) by a 3% aqueous trifluoroacetic acid solution (TFA), as well as for anthocyanins extracted from blueberry (Bluetta, high bush type). Capillary zone electrophoresis revealed that the PBR extract contained almost exclusively a single anthocyanin, which was identified as cyanidin 3-O-beta-D-glucoside (Cy 3-Glc) after purification by polyvinylpyrrolidone column chromatography. In contrast, 11 anthocyanins were identified in the blueberry extract. PBR extract showed slightly weaker superoxide scavenging and crocin bleaching activities than blueberry extract did. Both PBR and blueberry extracts, however, showed 10 to 25 times stronger activity than the same concentration of Trolox used as a reference antioxidant. It was further noted that the purified Cy 3-Glc from PBR extract retained approximately 74% of the antioxidant activity (both crocin bleaching and superoxide scavenging) observed in the original TFA extract. The hydroxyl radical scavenging activity of both extracts was several times weaker than that of the same concentration of Trolox, although the PBR extract showed approximately two times stronger activity than blueberry extract did. The hydroxyl radical scavenging activity of the purified Cy 3-Glc from PBR, however, decreased to approximately 20% of that of the original PBR extract. These results indicate that the anthocyanin Cy 3-Glc contributes to the antioxidant activity of PBR through its strong superoxide radical but not hydroxyl radical scavenging activity.


FEBS Letters | 1978

The role of tyrosine in the proton pump of bacteriorhodopsin

Tetsuya Konishi; Lester Packer

Light-induced proton pump activity of bacteriorhodopsin is a consequence of a photoreaction cycle composed of a number of distinct spectroscopically distinguishable transient species [ 1,2] . The 4 1 2-nm absorbing intermediate is a key component because it is a measure of the deprotonation and reprotonation of the retinal Schiff base [3-51 . The origin of the proton donated to the Schiff base and the specific amino acids which accept the released proton have not yet been identified. Previous studies in our laboratory have demonstrated that chemical modification of tryptophan groups of the molecule causes loss of the 570-nm absorption of the chromophore and a marked inhibition in the decay of the 4 12-nm species, particularly when half or more of the tryptophan residues have been modified [6] . The total number of tryptophan residues is between 4-7 [7]. This suggests that 2-3 residues are in close proximity to the retinal chromophore. In the present study we have investigated the role of tyrosine to determine whether this aromatic amino acid is also important in determining chromophore environment, since tyrosine is a potential donor or acceptor of protons for the Schiff base of the lysine where retinal is attached to the protein. The pH dependence of the decay of the 4 12-nm species indicated that the groups involved had a pK > 11, i.e. it was in the range where tyrosine residues are ionized. Furthermore, modification of bacteriorhodopsin by iodination showed that the loss of l-2 of the 11 tyrosine residues caused marked inhibition of photocycling. These results indicate that tyrosine residues are involved in reprotonation of


Journal of Agricultural and Food Chemistry | 2008

Effects of anthocyanins on psychological stress-induced oxidative stress and neurotransmitter status.

M. Mamunur Rahman; Takashi Ichiyanagi; Tadazumi Komiyama; Shinji Sato; Tetsuya Konishi

There is strong evidence that oxidative stress participates in the etiology of neurodegenerative diseases such as Parkinsons, and Alzheimers diseases. Moreover, emotional stress effects in the central nervous system play a vital role in homeostasis. The protective effect of anthocyanins on the cerebral oxidative stress was studied using the whiskers cut model. In mice, such treatment causes psychological or emotional distress leading to oxidative stress in tissues. To investigate the in vivo antioxidant activity of anthocyanins, an extract of Vaccinium myrtillis L., an anthocyanin mixture, was orally administered (100 mg/kg of body weight.) to mice for 7 days, and then psychological stress was assessed by cutting off their whiskers. Whisker removal increased both protein carbonyl formation and lipid peroxidation in the brain, heart, kidney, and liver. Further, the levels of oxidative markers showed regional differences in the brain. Concomitantly, dopamine neurotransmitter levels were altered in both the midbrain and the brain cortex. Orally administered anthocyanins were also active in the brain, suppressing stress-induced cerebral oxidative stress and dopamine abnormalities in distressed mice. These effects of anthocyanin treatment suggest their possible usefulness for the treatment of cerebral disorders related to oxidative stress.


Free Radical Research | 2000

The lactate-dependent enhancement of hydroxyl radical generation by the Fenton reaction

M. Aktar Ali; Fumihiko Yasui; Seiichi Matsugo; Tetsuya Konishi

The effect of lactic acid (lactate) on Fenton based hydroxyl radical (·OH) production was studied by spin trapping, ESR, and fluorescence methods using DMPO and coumarin-3-carboxylic acid (3-CCA) as the ·OH traps respectively. The ·OH adduct formation was inhibited by lactate up to 0.4mM (lactate/iron stoichiometry = 2) in both experiments, but markedly enhanced with increasing concentrations of lactate above this critical concentration. When the H2O2 dependence was examined, the DMPO-OH signal was increased linearly with H2O2 concentration up to 1 mM and then saturated in the absence of lactate. In the presence of lactate, however, the DMPO-OH signal was increased further with higher H2O2 concentration than 1 mM, and the saturation level was also increased dependent on lactate concentration. Spectroscopic studies revealed that lactate forms a stable colored complex with Fe3+ at lactate/Fe3+ stoichiometry of 2, and the complex formation was strictly related to the DMPO-OH formation. The complex formation did not promote the H2O2 mediated Fe3+ reduction. When the Fe3+-lactate (1:2) complex was reacted with H2O2, the initial rate of hydroxylated 3-CCA formation was linearly increased with H2O2 concentrations. All the data obtained in the present experiments suggested that the Fe3+-lactate (1:2) complex formed in the Fenton reaction system reacts directly with H2O2 to produce additional ·OH in the Fenton reaction by other mechanisms than lactate or lactate/Fe3+ mediated promotion of Fe3+/Fe2+ redox cycling.


The American Journal of Chinese Medicine | 2003

Role of Component Herbs in Antioxidant Activity of Shengmai San — A Traditional Chinese Medicine Formula Preventing Cerebral Oxidative Damage in Rat

Haruyo Ichikawa; Xuejiang Wang; Tetsuya Konishi

Traditional Chinese medicine (TCM) is an attractive model for studying antioxidant-based composite therapy. We previously reported that Shengmai San (SMS), a TCM formulation for treating cardiac disorders, inhibited cerebral oxidative damage in rats when evaluated by both glutathione peroxidase (GPX) activity loss and thiobarbituric acid reactive substance (TBARS) formation after forebrain ischemia-reperfusion. In the present study, we further examined the preventive effect of SMS and related decoctions composed of three component herbs (Panax ginseng, Ophiopogon japonicus and Schisandra chinensis) against oxidative brain injury to rationalize the complex formulation of SMS. Schisandra chinensis itself and decoctions containing it all inhibited TBARS formation in vivo. In contrast, Ophiopogon japonicus itself and formulations containing it had little effect on TBARS formation. GPX activity loss in vivo, on the other hand, was completely prevented only by SMS and Ophiopogon japonicus itself. A comparison of the in vitro antioxidant potential of SMS and related decoctions and in vivo effectiveness in preventing cerebral oxidative damage revealed that all the in vitro antioxidant indices examined here essentially correlated well with inhibition of TBARS formation in vivo. DPPH quenching and crocin bleaching activities showed particularly good correlation, and then, superoxide scavenging activity followed. However, none of them correlated with the inhibition of GPX activity loss in vivo. The role of each component herb is also discussed for the SMS effect.


Biochemical and Biophysical Research Communications | 1976

Light--dark conformational states in bacteriorhodopsin

Tetsuya Konishi; Lester Packer

Summary Dark adapted or illuminated preparations of purple membrane fragments from Halobacterium halobium were treated with bifunctional crosslinking reagents. Glutaraldehyde (7.5 A length) and dimethyl adipimidate (8.5 A length) showed marked differences in their affect on proton pump activity when treated in the dark and under illumination, respectively; but there was no significant difference in activity after light-dark treatment in the case of dimethyl suberimidate (11.5 A length). Net proton pump activity was also found to increase after imidoester treatment. The changes in proton pump activity seemed to have no direct correlation with the loss of free amino groups, but tryptophanyl residues seem involved. It is concluded that bacteriorhodopsin can exist in two chemically distinguishable conformational states in the dark and light, respectively.


The American Journal of Chinese Medicine | 2006

Prevention of Cerebral Oxidative Injury by Post-ischemic Intravenous Administration of Shengmai San

Haruyo Ichikawa; Lei Wang; Tetsuya Konishi

Shengmai San (SMS) is a traditional Chinese medicine (TCM) comprising three different herbal components, Panax ginseng, Ohiopogon japonicus and Fructus schisandrae and has been used for treating coronary heart diseases (Bensky and Barolet, 1990). It was shown that SMS effectively prevented cerebral oxidative injury in rats when it administered into the duodenum before cerebral ischemia-reperfusion. In the present study, we examined whether post-ischemic administration of SMS can ameliorate cerebral ischemia-reperfusion injury in rats as well. Results showed that SMS injected immediately after ischemia also prevented the ischemia-reperfusion injury, when the effect was evaluated by the formation of protein carbonyl and thiobarbituric acid reactive substance (TBARS), and the loss of glutathione peroxidase (GPX). The preventative potential of SMS was decreased rapidly dependent on the time lag until SMS was injected after ischemia. However, it was noted that intravenously administered SMS protected the oxidative injury approximately 30% even after 60 min of reperfusion in terms of protein carbonyl formation. It is thus suggested that SMS injection might be useful for preventing the progression of injury in cerebral infarction after stroke.


Current Pharmaceutical Biotechnology | 2010

Squalene as Novel Food Factor

Hari N. Bhilwade; Naoto Tatewaki; Hiroshi Nishida; Tetsuya Konishi

Currently, health beneficial roles of natural products attract much attention and diverse functional ingredients have been extensively studied their preventive effect in many diseases such as cardiovascular diseases and cancer. Squalene is one of those examples. It distributes in nature from plant to animal but extraordinarily concentrated in the liver of certain species of shark (Squalidae family) as it was first identified as a healing substance in the shark liver oil. It is now well-known that squalene is the physiological substance functioning in animal as the precursor of cholesterol biosynthesis. On the other hand, it has long history of using as an attractive resource for functional food, supplement or even pharmaceutics because it has unique physical property and wide variety of physiological functions such as anticancer and anti-hyper cholesterolemia. The antioxidant and oxygen carrying properties of squalene predicts its potential in preventing cardiovascular disease. We reviewed recent progress in functional studies of squalene both in vitro and in vivo models.


FEBS Letters | 1977

Chemical modification of bacteriorhodopsin with N-bromosuccinimide

Tetsuya Konishi; Lester Packer

Received 20 May 1977 1. Introduction Bacteriorhodopsin in the purple membrane of halophilic bacteria functions as a light-driven proton pump. Proton translocation is driven by light absorp- tion by the retinal chromophore [1 ], but the way in which the chromophore excitation interacts with protein, and the process of vectorial proton transloca- tion which involve the apo-protein are not yet well characterized. There is evidence that deprotonation and reprotonation of the Schiff base at the site of attachment of retinal to the protein is a primary step in proton translocation. The deprotonated intermediate state is detected by an absorption band at 412 nm during the photoreaction cycle [2-5]. The amino acid residues involved in this reaction and in the movement of the proton through the protein molecule are unclarified. Chemical modification of bacteriorhodopsin in purple membrane preparations is a good approach to study such questions because this protein is the only one in the preparation, and because it exhibits considerable stability [1,6]. In a previous study, we demonstrated that modification of amino groups using certain lysine specific reagents (imidoesters) and glutaraldehyde inhibited proton pump activity concommitant with a loss of intrinsic tryptophan fluorescence [7]. Oesterhelt and Hess [9] found a decrease of tryptophan fluorescence during illumination of purple membranes in ether saturated salt solutions. Furthermore Bensasson et al. [8] have proposed that in mammalian rhodopsin, tryptophan residues interact with the retinal Schiff base to form a charge transfer complex resulting in a large red shift of chromophore absorption. A similar situation may occur in the case of bacteriorhodopsin. In the present study the effect of a tryptophan specific reagent, N-bromosuccinimide, on bacteriorhodopsin has been investigated. Correlation of chemical modification tryptophan residues by this reagent with measurements of the formation the 412 nm photoreaction cycle intermediate and chromophore absorption, reveal that tryptophan residues are essential for proton pump activity. 2. Materials and methods Purple membrane preparations kindly provided by Dr J. Lanyi (NASA-Ames Research Center) containing 4-8 gM of bacteriorhodopsin, as calculated from 570 nm absorption using the molar extinction coefficient of 63 000 M -t cm-1, [9] were employed in experiments. Absorption spectra were recorded in a Cary 14 spectrophotometer and difference spectra were measured in the Aminco Chance DW2 dual wavelength spectrophotometer. The height of the 412 nm peak induced by a single flash is a direct indication of the number of bacteriorhodopsin molecules photocycling, and therefore provides an assessment of proton pump activity. The rate of decay the 412 nm intermediate is proportional to the kinetics of proton pump activity. Flash photometry was carried out in an apparatus designed for these measurements in our laboratory which contained a photoflash unit (Vivitar 283) 1 ms maximum flashes from a xenon lamp. A pair of narrow band interference filters with a peak transmission of 410 nm (Baird Atomic series) were used to isolate the


Iubmb Life | 1998

Synthesis and antioxidant activity of water‐soluble chitosan derivatives

Seiichi Matsugo; Minako Mizuie; Michiko Matsugo; Rie Ohwa; Hiromi Kitano; Tetsuya Konishi

We prepared three different water‐soluble chitosan derivatives by the acylation of chitosan with corresponding acid anhydrides. The extent of acylation was determined by using the electric conductivity method. All of the chitosan derivatives were soluble enough to examine the respective mltioxidant activity in aqueous media. The chitosan derivatives inhibited thiobarbituric acid reactive substrate (TBARS) formation in t‐butyl hydroperoxide and benzoyl peroxide induced lipid peroxidations. However, they did not show any scavenging activity toward superoxide.

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Lester Packer

University of California

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Takashi Ichiyanagi

Niigata University of Pharmacy and Applied Life Sciences

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Yoshihiko Hatano

Niigata University of Pharmacy and Applied Life Sciences

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M. Mamunur Rahman

Niigata University of Pharmacy and Applied Life Sciences

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Vijayasree V. Giridharan

University of Texas Health Science Center at Houston

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Shinji Sato

Niigata University of Pharmacy and Applied Life Sciences

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