Biomedical subjects

J Terao

Publications and source records attributed to J Terao.

At least 55 records · Page 3Linked to original sources

PubMed1998

beta-Glucosidase activity in the rat small intestine toward quercetin monoglucosides.

In order to evaluate the positional specificity for a glucoside group in the hydrolysis of flavonoid glucosides in the rat small intestine, beta-glucosidase activity was measured with the quercetin monoglucosides, quercetin-3-O-beta-D-glucopyranoside (Q3G), quercetin-4'-O-beta-D-glucopyranoside (Q4'G) and quercetin-7-O-beta-D-glucopyranoside (Q7G), as well as with quercetin-3-O-rutinoside (rutin) and p-nitrophenyl-beta-D-glucopyranoside (NPG) by using the HPLC technique. Enzymes were prepared from rat small intestinal mucosa of the duodenum, jejunum and ileum, among which the enzyme activity of the jejunum was highest for all the glycosides tested. Q4'G was the richest substrate for a beta-glucosidase solution among these glycosides, while rutin and NPG were both poor substrates. This suggests that dietary flavonoid glucosides are primarily hydrolyzed and liberated aglycones in the jejunum.

Animals↗

PubMed1998

Antioxidative activity of carp blood plasma on lipid peroxidation.

Antioxidative activity of carp blood plasma was estimated by measuring hydroperoxides formed by liposome peroxidation during the exposure of liposomes to AAPH. Ascorbic acid of high concentration, uric acid of low content, and tocopherol formed special protective system against lipid poroxidation in fish plasma. The decrease of uric acid, ascorbic acid, and tocopherol showed synergism of ascorbic acid and tocopherol, uric acid, and tocopherol. Carp blood plasma with a low concentration of protein (about 2%) and SH groups (88 microM) had a great effect on the antioxidative activity, as the effects of ascorbic acid, uric acid, and tocopherol were dramatically extended. Dialysed carp protein also displayed a very strong antioxidative activity on lipid peroxidation of a multilayer liposome system.

Adult↗

PubMed1998

Antioxidative activities of several marine polysaccharides evaluated in a phosphatidylcholine-liposomal suspension and organic solvents.

The antioxidative activities of several water-soluble marine polysaccharides, alginate (ALG), alginate sulfate (SALG), propylene glucolalginate sodium sulfate (PSS), propylene glucol mannuronate sulfate (PGMS), the oligosaccharide of chitosan (OLC), N,O-carboxymethyl chitosan (NOCC) and hydroxypropylated chitosan (HPC), were examined in a phosphatidylcholine (PC)-liposomal suspension containing the water-soluble radical emitter, 2,2'-azobis (2-amidinopropane) dihydrochloride. In the suspensions containing OLC and SALG, the initial rates of PC-OOH accumulation were 2.78 x 10(-8) MS-1 and 2.88 x 10(-8) MS-1, respectively, while all the polysaccharides tested showed antioxidative activity. Liposoluble marine polysaccharides, hexanoyl chitin (HCH) and an N-benzoylhexanoyl chitosan (NBHC) solution, also retarded the hydroperoxide accumulation of methyl linoleate by effectively trapping peroxide radicals in organic solvents when the radical chain reaction had been initiated by 2,2'-azobis (2,4-dimethylvaleronitrile). The kinetic data presented indicate that the alginate and chitin derivatives can be expected to play a role in the antioxidative mechanism of biological systems.

Alginates↗

PubMed1998

Synthesis of a novel phosphate ester of a vitamin E derivative and its antioxidative activity.

A novel phosphate ester containing a chromanol structure was synthesized from 1,2-diacyl-sn-glycero-3-phospho-2'-hydroxyethyl-2',5',7',8'-tetramethyl- 6' -hydroxychroman (PCh) by hydrolysis catalyzed by phospholipase C from Bacillus cereus. The structure of the product was found by spectral analyses to be 2-(2',5',7',8'-tetramethyl-6'-hydroxychromanyl)ethylphosphate++ + (Ch-P). Ch-P was highly soluble in the aqueous phase at neutral pH values and exerted higher antioxidative activity than alpha-tocopherol and PCh in the Fe(III)/ascorbic acid-catalyzed peroxidation of a fish oil emulsion and the autoxidation of a rat brain homogenate.

Animals↗

PubMed1997

Synthesis of a novel vitamin E derivative, 2-(alpha-D-glucopyranosyl) methyl-2,5,7,8-tetramethylchroman-6-ol, by alpha-glucosidase-catalyzed transglycosylation.

A novel derivative of vitamin E, vitamin E glucoside, was synthesized from 2-hydroxymethyl-2,5,7,8-tetramethylchroman-6-ol and maltose in a solution containing DMSO by transglycosylation with alpha-glucosidase from Saccharomyces species. The glycosylated product was identified as 2-(alpha-D-glucopyranosyl)methyl-2,5,7,8-tetramethylchroman-6-ol (TMG) by mass spectrometry and nuclear magnetic resonance spectroscopy. The optimal pH of transglycosylation was 5.5, and the yield of TMG increased as the concentration of maltose increased. TMG has high solubility in water (> 1 x 10(3) mg/mL). The 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity of TMG was found to be nearly the same as those of alpha-tocopherol, Trolox (2-carboxy-2,5,7,8-tetramethylchroman-6-ol), and ascorbic acid.

Antioxidants↗

PubMed1997

Kinetics and dynamics of singlet oxygen scavenging by alpha-tocopherol in phospholipid model membranes.

Scavenging of singlet oxygen (1O2) by alpha-tocopherol (alpha-Toc) was investigated in liposomes. 1O2 was generated by photoirradiation in the presence of two photosensitizers, water-soluble methylene blue (MB) and lipid-soluble 12-(1-pyrene)dodecanoic acid (PDA). The rates of oxidation of alpha-Toc differed depending on the photosensitizing dye and the membrane charge: in the MB-system, alpha-Toc was oxidized fast in negatively charged dimyristoylphosphatidylcholine (DMPC) liposomes containing dicetylphosphate (DCP) and slowly in neutrally charged DMPC liposomes and positively charged DMPC liposomes containing stearylamine (SA), but in the PDA-system, the oxidation rate was independent of the membrane charge. The charge-dependent difference in the MB-system would be due to the site of 1O2 generation depending on the charge-dependent distribution of MB, because positively charged MB increased the zeta-potential of DCP-DMPC liposomes by its interaction with DCP at the membrane surface, but changed the zeta-potentials of DMPC and SA-DMPC liposomes less because of its location in the bulk water phase. The oxidation rate of alpha-Toc in liposomes was different from that in EtOH solution: in the MB system, the oxidation rate was faster in EtOH solution than in DMPC or SA-DMPC liposomes but the same as that in DCP-DMPC liposomes. However, in the PDA system, the oxidation rate was slower in EtOH solution than in DMPC liposomes with or without a charge. Membrane fluidity changed the rate of alpha-Toc oxidation in liposomes, the rate being higher in the liquid crystalline phase than the gel phase, as judged by the higher rate in DMPC liposomes than in dipalmitoylphosphatidylcholine (DPPC) liposomes at 30 degrees C. The rate constants of alpha-Toc for scavenging, the chemical reaction and physical quenching of 1O2 were determined in membranes using DCP-DMPC liposomes labeled with 1,3-diphenyl-isobenzofuran (DPBF), which traps 1O2. These constants differed in the two photosensitizing systems, being higher in the MB-system than in the PDA-system, and were lower than those in EtOH solution.

Electrochemistry↗

PubMed1997

Accumulation and clearance of capsanthin in blood plasma after the ingestion of paprika juice in men.

The pharmacokinetics of dietary capsanthin was measured in four male volunteers to assess the bioavailability of oxygenated carotenoids (xanthophylls). Capsanthin was used because this carotenoid was not detected in the men's plasma before ingestion of paprika juice. Supplementing capsanthin-rich paprika juice for 1 wk (equivalent to three doses of 5.4 micromol capsanthin/d; 16.2 micromol/d), the level of capsanthin reached a plateau (0.10-0.12 micromol/L) between d 2 and 7 and was not detectable by d 16. Capsanthin was distributed in the plasma lipoproteins (VLDL, 13 +/- 3%; LDL , 44 +/- 3%; HDL, 43 +/- 3%) at the end of the experiment. In a separate experiment involving the single ingestion of paprika juice (equivalent to 34.2 micromol capsanthin) in the same men, the plasma concentration of capsanthin ranged from 0.10 to 0.29 micromol/L at 8 h after ingestion. In contrast, the elevation of the plasma concentration of an acyclic hydrocarbon carotenoid, lycopene, by a single ingestion of tomato soup (equivalent to 186.3 micromol lycopene) in the same subjects was minimal (0.02-0.06 micromol/L). The areas under the curves (AUC) for capsanthin between 0 and 74 h and for lycopene between 0 and 72 h were 4.68 +/- 1.22 and 0.81 +/- 0.17(micromol.h)/L, respectively. The half-lives (t1/2) were calculated to be 20.1 +/- 1.3 and 222 +/- 15 h for capsanthin and lycopene, respectively. We conclude that the clearance of capsanthin is much faster than that of lycopene, although capsanthin is transported into plasma lipoproteins in larger amounts. This polar carotenoid may be metabolized in the human body more rapidly than lycopene. These data justify further research on the physiological functions of capsanthin and other xanthophylls.

Adult↗

PubMed1996

Reactivity of mammalian 15-lipoxygenase with phospholipids in large unilamellar liposomes.

The reactivity of rabbit reticulocyte 15-lipoxygenase (15-LOX) with phosphatidylcholine (PC) possessing linoleic acid (LA-PC), arachidonic acid (AA-PC), or docosahexaenoic acid (DHA-PC) was investigated by measuring oxygen uptake in the suspension of large unilamellar liposomes (LUV). The 15-LOX reaction with PC LUV was found to follow Michaelis-Menten kinetics. The apparent values of the Michaelis constants (K(m)) of LUV of LA-PC, AA-PC, and DHA-PC were nearly the same (1.0-1.2 mM). However, the maximum velocity (Vmax) of DHA-PC was obviously two to three times lower than those of LA-PC and AA-PC. On the other hand, the oxidizability of PC per bis-allylic H of unsaturated fatty acids in the free radical chain reaction of LUV decreased with increasing degree of unsaturation, that is, LA-PC > AA-PC > DHA-PC. These results suggested that the oxidizability of the DHA moiety incorporated into biomembranes is not necessarily high in lipoxygenase reaction as in free radical chain reaction.

Animals↗

PubMed1996

Assay of beta-carotene 15,15'-dioxygenase activity by reverse-phase high-pressure liquid chromatography.

beta-Carotene 15,15'-dioxygenase catalyzes the conversion of beta-carotene into two molecules of retinal. Although this enzyme reaction is the first step in providing animals with vitamin A, there is little knowledge about its regulation in mammals. In order to facilitate studies on this enzyme, we have developed a rapid and simple assay method for the measurement of retinal formation by beta-carotene dioxygenase. All-trans-beta-carotene solubilized in aqueous solution with Tween 40 was incubated with an enzyme preparation of rat tissue at 37 degrees C for 30 min. Then, the reaction was stopped with a formaldehyde treatment followed by addition of acetonitrile. After centrifugation, the supernatant was directly subjected to high-pressure liquid chromatographic analysis of retinal. This assay method did not involve any vigorous extraction or concentration procedure. All-trans- and 13-cis-retinals, major geometric isomers found in the reaction mixture, were coeluted at 7.5 min, but they were well separated from other possible metabolites of beta-carotene such as retinoic acid, retinol, and apocarotenals. Moreover, the recovery of retinal reached more than 93% and the detection limit of standard retinal was 0.2 pmol/0.2 ml of reaction mixture. Enzyme activities of rat tissues were 694, 180, 16, 8, and approx 1 pmol retinal/mg protein/h in the intestine, liver, brain, lung, and kidney homogenates, respectively.

Animals↗

PubMed1996

Stoichiometric conversion of all trans-beta-carotene to retinal by pig intestinal extract.

beta-Carotene and other provitamin A carotenoids are major dietary sources of vitamin A for humans and for many animals throughout the world. Two pathways for this oxidative reaction in mammals are: (1) central cleavage by beta-carotene 15,15'-dioxygenase (EC 1.13.11.21) to yield two molecules of retinal per molecule of beta-carotene consumed and (2) eccentric (or random) cleavage via several beta-apo carotenals to yield one molecule of retinal and various smaller fragments per molecule of beta-carotene oxidized. By the use of improved methods to minimize nonenzymatic reactions and to measure isomers of retinal, the mean experimentally measured molar ratio of retinal formed to beta-carotene consumed by pig intestinal preparations (800 and 10,000g supernatants) was 1.88 +/- 0.08, close to the theoretical value of 2.0 for central cleavage. beta-Apo carotenals, retinol, and retinoic acid were detected, if at all, in trace amounts during incubation. Thus, preparations of pig intestinal mucosa, which is considered a good physiologic model for human intestine, clearly convert beta-carotene to retinal, in large part if not solely, by central cleavage. Whether eccentric cleavage plays a greater role in vivo than it does in vitro is still uncertain.

Animals↗

PubMed1996

Coulometric detection in high-performance liquid chromatographic analysis of cholesteryl ester hydroperoxides.

A highly sensitive and simple method for the determination of cholesteryl ester hydroperoxides (ChE-OOH) was developed using high-performance liquid chromatography (HPLC) with coulometric electrochemical detection. The lowest detectable level by this technique was 2 pmol for cholesteryl linoleate hydroperoxides at the signal-to-noise ratio of 3. This method was applied to the determination of ChE-OOH presumably present in human plasma. Although ChE-OOH could not be detected, the ChE-OOH level in the fluid was estimated to be less than 27 nM. It was found that the extraction efficiency of an internal standard, cholesteryl nervonate, was decreased by lowering its amount spiked to the plasma. The concentration of ChE-OOH in human plasma and plasma lipoprotein, which were peroxidized with a radical initiator in vitro, could be determined by use of this standard. HPLC-coulometric technique is, therefore, useful to measure the peroxidation of plasma lipids in vitro.

Cholesterol Esters↗

PubMed1996

Antioxidant behaviors of vitamin E analogues in unilamellar vesicles.

The antioxidant behaviors of vitamin E and its analogues, 2,2,5,7,8-pentamethyl-6-hydroxychroman and 1,2-diacyl-sn-glycero3-phospho-2'-(hydroxyethyl)-2'- 5',7',8'-tetramethyl-6'-hydroxychroman, were studied in unilamellar vesicles. The two analogues scavenged aqueous radicals generated from azo compounds more efficiently than vitamin E. On the other hand, vitamin E scavenged the lipid peroxyl radicals preferentially. It is concluded that the superior antioxidant activity of vitamin E is attributed to its location suitable for breaking the chain propagation reaction.

Antioxidants↗

PubMed1995

Antioxidative activity of quercetin and quercetin monoglucosides in solution and phospholipid bilayers.

The antioxidative effect of quercetin, quercetin 3-O-beta-D-glucopyranoside (Q3G), quercetin 4'-O-beta-D-glucopyranoside (Q4'G) and quercetin 7-O-beta-D-glucopyranoside (Q7G) was examined in solution and liposomal phospholipid suspension. First, their peroxyl radical-scavenging activities were investigated by measuring the inhibition of hydroperoxidation of methyl linoleate initiated by a radical initiator, 2,2'-azobis(2,4-dimethylvaleronitrile) (AMVN). Quercetin exhibited the highest peroxyl radical-scavenging activity judging from the rate of hydroperoxidation during the induction period (Rinh) and the length of induction period (tinh). Although Q7G showed an induction period, its Rinh was higher and its tinh was lower than that of quercetin. Neither Q3G nor Q4'G gave a clear induction period in the curve of hydroperoxide formation. The rate of hydroperoxidation in the presence of Q3G was higher than Rinh of quercetin and the oxidative loss of Q3G was much slower than quercetin or Q7G when exposed to AMVN in solution. Q4'G exerted little inhibition compared to Q3G or Q7G. Next, the antioxidative activity of quercetin and its monoglucosides in phospholipid bilayers was examined by measuring the inhibition of lipid peroxidation in large unilamellar vesicles composed of egg yolk phosphatidylcholine (PC) and a water-soluble radical initiator. They retarded the accumulation of PC-hydroperoxides and the induction period increased in the order of Q4'G < Q3G approximately Q7G < quercetin. It is therefore concluded that quercetin acts as an antioxidant more efficiently than its monoglucosides when phospholipid bilayers are exposed to aqueous oxygen radicals.

Antioxidants↗

PubMed1995

Effect of d-alpha-tocopherol analogues on lipoxygenase-dependent peroxidation of phospholipid-bile salt micelles.

In order to know whether or not vitamin E acts as an effective antioxidant in lipoxygenase-dependent peroxidation of phospholipids, the effect of vitamin E and vitamin E analogues, 2,2,5,7,8-pentamethyl-6-hydroxychroman (PMC) and 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox C), was investigated in enzymatic lipid peroxidation of bile salt micelles of pig liver phosphatidylcholine (PC) using soybean lipoxygenase. 15-Hydroperoxy-5,8,11,13-eicosatetraenoic acid was exclusively produced by the reaction with the PC molecular species containing arachidonic acid moiety, indicating that the hydroperoxidation of pig liver PC entirely progresses through the enzymatic reaction. PMC suppressed the accumulation of PC-hydroperoxides (PC-OOH) more efficiently than either d-alpha-tocopherol (alpha-Toc) or Trolox C, and 50% inhibition concentration by PMC was close to that of quercetin, a known lipoxygenase inhibitor from natural origin. The antioxidant activity of PMC was also superior to that of either alpha-Toc or Trolox C in ferrous ion-induced nonenzymatic oxidation of PC micelles in the presence of a trace amount of PC-OOH, although the radical-scavenging activities of these compounds in solution were similar or comparable to one another. In conclusion, PMC is more effective than alpha-Toc as an inhibitor of lipoxygenase reaction with phospholipids and of autoxidation in phospholipids. The phytyl chain of alpha-Toc seems to be unfavorable for exerting an inhibitory effect on lipoxygenase reaction with phospholipid-bile salt micelles.

Animals↗

PubMed1995

Effects of rat bile-pancreatic juice on Fe2+ induced peroxidation of phospholipids.

The effects of rat bile-pancreatic juice (BPJ) on Fe2+ induced oxidation of soybean phosphatidylcholine (PC) was monitored to investigate the influence of this digestive juice on oxidative damage in the gastrointestinal tract. A large volume of BPJ (50% in the suspension of PC, v/v) suppressed the lipid peroxidation, but a smaller volume had the reverse effect. BPJ could decompose free fatty acid hydroperoxides (FFA-OOH) at a lower concentration (approximately 0.2 mM) completely, although its phospholipase activity liberated FFA-OOH from PC hydroperoxides. Sodium deoxycholate enhanced the Fe2+ induced oxidation of PC in a concentration-dependent manner when PC was suspended in the buffer. Boiled BPJ suppressed Fe2+ induced and peroxyl radical initiated oxidation of sodium deoxycholate micelles of soybean PC up to approximately 50% (v/v). It was strongly suggested that rat BPJ had a biphasic effect on Fe2+ induced oxidation of phospholipids depending on the enhancement by bile salts and the inhibition by antioxidant components with radical-scavenging activity and hydroperoxide-decomposing activity.

Animals↗

PubMed1994

Protective effect of epicatechin, epicatechin gallate, and quercetin on lipid peroxidation in phospholipid bilayers.

Antioxidative effect of (-)-epicatechin,(-)-epicatechin gallate, and quercetin was examined by measuring the inhibition of lipid peroxidation in large unilamellar liposomes composed of egg yolk phosphatidylcholine (PC). These catechol-type flavonoids were stable in the liposomal suspension. They retarded the accumulation of PC-hydroperoxides depending on their concentrations when the suspension was exposed to an water-soluble radical initiator, 2,2'-azobis(2-amidinopropane)hydrochloride (AAPH). Their inhibitory effects lasted longer than that of alpha-tocopherol. When each flavonoid and alpha-tocopherol were mixed in the liposomes, epicatechin and epicatechin gallate disappeared in favor of alpha-tocopherol. Quercetin also decreased faster than alpha-tocopherol in the initial stage of incubation. Kinetic studies of the inhibition of radical chain oxidation of methyl linoleate in solution demonstrated that the rate constants for the inhibition of oxidation by these flavonoids (kinh) were 5-20 times smaller than that by alpha-tocopherol. It is likely that the flavonoids are localized near the surface of phospholipid bilayers suitable for scavenging aqueous oxygen radicals and thereby they prevent the consumption of lipophilic alpha-to-copherol. Epicatechin and epicatecin gallate gave smaller kinh values than quercetin. Voltammograms of these compounds showed that electron-donating ability of catechins was lower than that of quercetin. However, antioxidative effects of catechins were comparable to that of quercetin in AAPH-initiated peroxidation of the liposomal suspension. It is concluded that catechins and quercetin serve as powerful antioxidants against lipid peroxidation when phospholipid bilayers are exposed to aqueous oxygen radicals.

Antioxidants↗

PubMed1994

Synthesis of a phosphatidyl derivative of vitamin E and its antioxidant activity in phospholipid bilayers.

A novel phospholipid containing a chromanol structure at its polar head group was synthesized from egg yolk phosphatidylcholine and 2,5,7,8-tetramethyl-6-hydroxy-2-(hydroxyethyl)chroman by transphosphatidylation catalyzed by phospholipase D from Streptomyces lydicus. The structure of the product synthesized was shown by spectral analysis to be 1,2-diacyl-sn-glycero-3-phospho-2'-hydroxyethyl- 2',5',7',8'-tetramethyl-6'-hydroxychroman. The phosphatidylchromanol (PCh) showed antioxidant activity against radical chain oxidation of methyl linoleate in solution in a manner similar to that of d-alpha-tocopherol (alpha-Toc) and 2,2,5,7,8-pentamethyl-6-chromanol. However, PCh was less effective as a chain-breaking antioxidant than was alpha-Toc when unilamellar egg yolk phosphatidylcholine liposomes were exposed to either a water-soluble or a lipid-soluble radical initiator. It is likely that the phospholipid nature of PCh affects the location and the mobility of the chromanol moiety in the membrane bilayer resulting in a decrease in antioxidant activity. On the other hand, the antioxidant activity of PCh was little different from that of alpha-Toc in unilamellar liposomes when exposed to a lipid-soluble radical initiator in the presence of ascorbic acid. It appears that PCh in phospholipid bilayers can be regenerated by ascorbic acid in aqueous phase as can be alpha-Toc. The new phospholipid, phosphatidylchromanol, should prove useful as a chain-breaking antioxidant in phospholipid membranes.

Antioxidants↗

PubMed1993

Reduction of fatty acid hydroperoxides by human parotid saliva.

Arachidonic acid hydroperoxide (15-hydroperoxyeicosatetraenoic acid; 15-HPETE) was introduced into human parotid saliva and incubated at 37 degrees C. Straight phase high-performance liquid chromatography analysis of the reaction mixture showed that 15-HPETE was detoxified to its reduced form, 15-hydroxyeicosatetraenoic acid, in the presence of glutathione. Therefore, it is concluded that human parotid saliva possesses fatty acid hydroperoxide-reducing ability. However, its effectiveness was found to be lower than that of blood plasma.

Adult↗