Significance of the equilibrium constant between serum ascorbate radical and ascorbic acids in man.

Sasaki, Ryo; Kobayasi, T.; Kurokawa, Toshiko; Shibuya, Daisuke; Tero‐Kubota, Shozo

doi:10.1620/tjem.144.203

Cited by 9 publications

(9 citation statements)

References 14 publications

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“…In animal exper- iments, sepsis has also been shown to increase Asc •-, indicating the involvement of oxidative stress with this health problem (69). Sasaki et al have investigated in human serum the use of Asc •signal intensity in combination with measurements of AscHand DHA as an indicator of oxidative stress in human health problems that range from aging to xenobiotic metabolism (70)(71)(72)(73)(74). Consequently, the ascorbate radical level in biological systems may be useful for monitoring free radical reactions in vivo, particularly when free radical production is low and other methods are insensitive.…”

Section: Ascorbate Radical As a Marker Of Free Radical-mediated Oxidamentioning

confidence: 99%

Catalytic Metals, Ascorbate and Free Radicals: Combinations to Avoid

Buettner¹,

Jurkiewicz²

1996

Radiation Research

803

601

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Trace levels of transition metals can participate in the metal-catalyzed Haber-Weiss reaction (superoxide-driven Fenton reaction) as well as catalyze the oxidation of ascorbate. Generally ascorbate is thought of as an excellent reducing agent; it is able to serve as a donor antioxidant in free radical-mediated oxidation processes. However, as a reducing agent it is also able to reduce redox-active metals such as copper and iron, thereby increasing the pro-oxidant chemistry of these metals. Thus ascorbate can serve as both a pro-oxidant and an antioxidant. In general, at low ascorbate concentrations, ascorbate is prone to be a pro-oxidant, and at high concentrations, it will tend to be an antioxidant. Hence there is a crossover effect. We propose that the "position" of this crossover effect is a function of the catalytic metal concentration. In this presentation, we discuss: (1) the role of catalytic metals in free radical-mediated oxidations; (2) ascorbate as both a pro-oxidant and an antioxidant; (3) catalytic metal catalysis of ascorbate oxidation; (4) use of ascorbate to determine adventitious catalytic metal concentrations; (5) use of ascorbate radical as a marker of oxidative stress; and (6) use of ascorbate and iron as free radical pro-oxidants in photodynamic therapy of cancer.

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Section: Ascorbate Radical As a Marker Of Free Radical-mediated Oxidamentioning

confidence: 99%

Catalytic Metals, Ascorbate and Free Radicals: Combinations to Avoid

Buettner¹,

Jurkiewicz²

1996

Radiation Research

803

601

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“…Control animals were given 1 ml of physiological saline intraperitoneally. K/ [H+] values were calculated as previously reported (Sasaki et al 1984). To see the in vitro effect of omeprazole, changes in ESR signal intensity of ARF were examined with the following solutions as previously described (Sasaki et al 1985) : (1) values in sera of the control and omeprazole-treated animals 7.4 (ascorbate solution plus the omeprazole solution).…”

Section: Methodsmentioning

confidence: 99%

Effect of Omeprazole on Ascorbate Free Radical Formation.

Ohara

Sasaki²,

Shibuya

et al. 1992

Tohoku J. Exp. Med.

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“…The K value of ascorbic acid was reported to be 4.5-5.4 X 10-9 in ascorbic acid solution [2], and 0.18-4.85 X 10-6, the mean being 1.08 X 10-6 in human serum in normal subjects [1]; the K value in serum is exceedingly larger than that in ascorbic acid solution. There are many factors affecting AFR content in serum, *To whom correspondence should be addressed .…”

mentioning

confidence: 98%

“…Previously we reported that there is an apparent equilibrium between RAsA, AFR, and DAsA in human serum, i.e., RAsA~AFR~DAsA, where RAsA is the reduced form, and DAsA, the oxidized form, of ascorbic acid; and AFR is ascorbate free radical. Since RAsA + DAsA = 2 AFR + H+, the K/ [H+] = [ AFR] 2/ [ RAsA ] [ DAsA ] can be calculated; and this K/[W] value (denoted as K value thereafter) is constant in healthy subjects regardless of total ascorbic acid concentration, age, and sex [1].…”

mentioning

confidence: 99%

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Use of K Value of Ascorbic Acid as a Clinical Index of Attack by Oxygen Radicals

Sasaki

Kurokawa

Shibuya

et al. 1989

J. Clin. Biochem. Nutr.

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The K value = [AFR]2/[RAsA] [DAsA ] (RAsA, reduced form of ascorbic acid; DAsA, oxidized form of ascorbic acid; AFR, ascorbate free radical), and changes in AFR concentration in human serum were examined after exposure to oxygen radicals. After the exposure, RAsA decreased, DAsA increased, and K value increased. Since the K value is constant in healthy subjects, it is regarded to be a clinical index to indicate the attack of oxygen radicals in living system. Whereas changes in AFR concentration in ascorbate solutions showed a one-way decrease after an initial increase, changes in serum were those of a persistent pattern with slight fluctuation after the initial increase. The difference was found to be attributable to the presence of a serum factor that inhibits ascorbate oxidation.

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Significance of the equilibrium constant between serum ascorbate radical and ascorbic acids in man.

Cited by 9 publications

References 14 publications

Catalytic Metals, Ascorbate and Free Radicals: Combinations to Avoid

Catalytic Metals, Ascorbate and Free Radicals: Combinations to Avoid

Effect of Omeprazole on Ascorbate Free Radical Formation.

Use of K Value of Ascorbic Acid as a Clinical Index of Attack by Oxygen Radicals

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