Author: Lee, Oi Yin
Title: The acute effect of epigallocatechin gallate (EGCG) on oxidative stress and antioxidant status
Degree: M.Sc.
Year: 2016
Subject: Hong Kong Polytechnic University -- Dissertations
Catechin
Antioxidants
Oxidative stress
Department: Department of Health Technology and Informatics
Pages: xviii, 154 pages : color illustrations
Language: English
Abstract: Introduction: An imbalance between reactive oxygen species (ROS) and antioxidants in favor of oxidants leads to a condition called oxidative stress, which potentially induces oxidative damage to biomolecules within the human body. Oxidative damage to various components is associated with increased risk of developing non-communicable diseases (NCDs), and it was evidenced that the achievement of improved in vivo antioxidant status from dietary supplementation was capable of lowering such oxidative attack. Extensive research studies were conducted to investigate the antioxidative property of natural antioxidants and the health benefits of antioxidant-rich green tea for a wide variety of NCDs, including diabetes, cardiovascular disease and different types of cancers, were reported. Such beneficial effects of green tea have been attributed to catechins, particularly epigallocatechin gallate (EGCG), the predominant catechin in green tea. Advantageous effect of regular consumption of green tea has been established in observation studies, however, the acute effects of a single dose of EGCG has not been well studied. This was the focus of this current study. Aim: To investigate the acute effect of ingestion of 800 mg of EGCG on biomarkers of oxidative stress and antioxidant status in human subjects. Methodology: This was a single arm interventional study involving 18 apparently healthy subjects who had a 2 week run-in period of daily consumption of 800 mg EGCG in powdered form. Afterwards, blood samples were collected immediately prior to and during 24 hours' post-ingestion of 800 mg EGCG. The biomarker of oxidative stress was plasma allantoin measured using high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) while the biomarker of antioxidant status was plasma total antioxidant capacity (TAC) measured using the ferric reducing/ antioxidant power (FRAP) assay. Plasma uric acid was measured as well using a commercial test kit to determine the corrected 'non-uric acid total antioxidant capacity' (non-UA FRAP). Results: As compared to pre-ingestion (fasting) value, plasma allantoin and uric acid concentration were found to be significantly (p<0.05) lower at up to 3 hours post-consumption. The non-UA FRAP value was significantly (p<0.05) increased for up to 10 hours (p<0.05) after the intake of EGCG. Plasma EGCG and allantoin concentrations were inversely correlated (free EGCG, r=-0.302, p=0.01; total EGCG, r=-0.414, p<0.001), plasma EGCG and uric acid were also inversely correlated (free EGCG, r=-0.370, p=0.006; total EGCG, r=-0.434, p=0.001) while plasma EGCG and the corrected TAC were directly correlated (free EGCG, r=0.634, p<0.001; total EGCG, r=0.499, p<0.001). Conclusion: The ingestion of a single dose of 800mg EGCG induced a transient decrease in oxidative stress and increased plasma antioxidant status. Further studies are recommended to investigate the long term beneficial effects of EGCG in those with increased risk of NCDs.
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