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The Antioxidant Activity of Green Tea in vivo.

Quartley, Benjamin J.P. (1996) The Antioxidant Activity of Green Tea in vivo. Doctoral thesis, University of Surrey (United Kingdom)..

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Abstract

The in vivo antioxidant activity of a dose of green tea which could realistically be achieved by habitual consumption of green tea beverage has been investigated in animals and humans. Initially methods for the analysis of biomarkers of oxidative damage in animals were set up and validated. Apparatus for the measurement of ethane exhalation was reactivated and the role of the gastrointestinal flora in ethane production investigated. There was no significant difference in ethane production between conventional and germ-fiee Lister Hooded rats fed either LAD 1 animal diet or a semi-synthetic diets containing 5% fish oil. Ethane production from germ-free rats fed a semi-synthetic diet containing maize oil was significantly greater than that from conventional animals fed the same diet. The gastrointestinal flora was therefore discounted as a significant source of ethane production in rats fed such diets. A method was also developed for the measurement of plasma and urinary malondialdehyde. Using these biomarkers the in vivo antioxidant activity of green tea was investigated in conventional and vitamin E-deficient Lister Hooded rats fed fish oil and maize oil diets similar to those used when investigating the role of the gastrointestinal flora in ethane production. All three biomarkers were significantly greater in animals fed the fish oil diet compared with animals fed the maize oil diet. Plasma malondialdehyde in conventional animals fed either diet, fish oil or maize oil, was significantly lower in animals provided with green tea beverage compared with animals maintained on normal drinking water. Addition of green tea extract to plasma samples immediately prior to development of the malondialdehyde-diethylthiobarbituric acid complex had no effect on their malondialdehyde content. Urinary malondialdehyde excretion from animals fed the tocopherol-stripped maize oil diet from weaning was significantly greater than that from animals weaned onto a similar maize oil diet containing α-tocopherol. Plasma malondialdehyde and ethane exhalation were not significantly affected by vitamin E status in animals fed the maize oil diets. Ethane exhalation and urinary malondialdehyde excretion from vitamin E-deficient animals fed the vitamin E-deficient fish oil diet were significantly greater than that from conventional animals fed a fish oil diet replete in vitamin E. This may have been a reflection of dietary peroxidation as well as the deficient nature of the animals. There was no evidence to suggest that green tea had antioxidant activity in the vitamin E-deficient animals. Following the animal studies the methodology for ethane and malondialdehyde analysis was transferred to humans. The in vivo antioxidant activity of green tea was then investigated in ostensibly health men aged 40-60 years. The study was conducted in smokers and non-smokers given a fish oil supplement in an attempt to increase antioxidant requirements. Prior to supplementation, ethane exhalation and urinary malondialdehyde excretion were significantly greater from smokers. Plasma malondialdehyde was not significantly affected by smoking status. Similarly, there was no significant difference in baseline levels of plasma protein carbonyls and lymphocyte DNA oxidation between smokers and non-smokers. Plasma antioxidant nutrients were also measured and were found to be consistently lower in smokers, with the exception of γ-tocopherol which was lower in non-smokers. There was, however, considerable inter-individual variability in plasma antioxidant nutrient concentrations and differences between smokers and non-smokers did not reach statistical significance. Fish oil supplementation increased plasma and urinary levels of malondialdehyde without affecting ethane exhalation in both groups, smokers and non-smokers. The magnitude of this effect was greater in smokers. Plasma protein carbonyls also increased in response to fish oil supplementation, although there was no change in lymphocyte DNA oxidation. Plasma concentrations of α-tocopherol and carotenoids were not significantly affected by fish oil supplementation in smokers and non-smokers. Fish oil supplementation did, however, result in a significant reduction in non-smokers’ plasma γ-tocopherol. Plasma triglycerides also decreased during the study, an observation suggestive of compliance with the requested consumption of fish oil capsules. With the exception of plasma retinol, none of the biomarkers selected were significantly affected by green tea.

Item Type: Thesis (Doctoral)
Divisions : Theses
Authors : Quartley, Benjamin J.P.
Date : 1996
Additional Information : Thesis (Ph.D.)--University of Surrey (United Kingdom), 1996.
Depositing User : EPrints Services
Date Deposited : 06 May 2020 14:37
Last Modified : 06 May 2020 14:43
URI: http://epubs.surrey.ac.uk/id/eprint/856287

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