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Kai On Chu, Kwok Ping Chan, Yaping Yang, Yongjie Qin, Wai Ying Li, Chi Pui Pang; Effect of high level of EGCG content in green tea extract on the catechins exposures profiles in different ocular compartment. Invest. Ophthalmol. Vis. Sci. 2014;55(13):4522.
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Epigallocatechin gallate (EGCG) is considered as the most abundant and potent compound in green tea extract (GTE). There is no evidence higher EGCG contents in GTE enhance biological effects. This study investigates the pharmacokinetics of GTE with high EGCG (70% w/w) content.
GTE with high EGCG was fed at 550 mg/kg intragastrically to SD rats, which were sacrificed at time points 5 min, 0.5, 1, 2, 4, 6, 10, 15, and 20 hours. The plasma, aqueous humor, vitreous humor, cornea, lens, retina, chloroid-sclera, were obtained for analyisis by high performance liquid chromatography with electro-chemical detection.
The specific exposure levels of catechins in the plasma at >0.15 hr/L, [gallocatechin (GC), catechin (C), epigallocatechin (EGC), and epicatechin (EC)], was higher than the levels of their gallate derivatives at ~0.01 hr/L [EGCG, gallocatechin gallate (GCG), epicatechin gallates (ECG), and catechin gallate (CG). Comparing with a previous study on GTE with low EGCG (30% w/w) , the level of C was higher than EC. The specific exposure of GC in the vitreous humor was 10 times higher in this study, with relative AUC of GC at 26.7 against 2.7. The catchin gallates derivatives, except GCG, were significant higher than catechins in the vitreous humor.
The specific exposure level accounts the input dose of different catechins from the extract and from the circulation. This value implicates the specificity of each catechin penetrating and retaining in a particular compartment. This study indicates high level of EGCG does not have significant effect on systemic absorption of other catechins. However, it has significant effect on the absorption of catechins in different ocular compartment but the lens. Whether this effect would indirectly affect the GTE biological effects on different ocular compartment requires further investigation.
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