The effect of formulation on the bioavailability of green tea catechins
Abstract
Consumption of green tea (Camellia sinensis), has been associated by epidemiological studies to prevention of several chronic diseases including cancer, cardiovascular disease and obesity. Further study using in vitro and animal models has also yielded promising results however human trials have fallen short of replicating results seen with in vitro and animal studies. These shortcomings are believed to be due, in part, to the poor absorption of catechins from tea and tea based products. Poor oral bioavailability of tea catechins is believed to be due in large part to digestive instability, poor intestinal uptake/transport and rapid metabolism and clearance. Previous research has demonstrated that green tea beverages formulated with ascorbic acid and citrus juices increase digestive stability in vitro and may influence intestinal uptake in cultured human intestinal cells. While promising further knowledge of how formulation may impact catechins bioavailability in vivo are required to define strategies positively influencing absorption of health promoting compounds from tea. To characterize the impact of formulation on catechin digestive stability, intestinal uptake and bioavailability in vivo green tea was formulated plain (GT), with sucrose (GT+S), with ascorbic acid (GT+AA) and with sucrose plus ascorbic acid (GT+SUC+AA). Catechin digestive stability and intestinal uptake were assessed using a coupled in vitro digestion/Caco-2 cell model. In vivo bioavailability was investigated in Sprague Dawley over 6h rats following acute oral dosing. Overall GT+S, GT+AA and GT+S+AA formulations significantly improved overall catechin digestive recovery relative to control by 31.4%, 15.3% and 37.2% respectively. Accumulation of EGC, EGCG and ECG by Caco-2 human intestinal cells was significantly (p<0.05) higher from test media produced with digesta of GT+S+AA than other formulations. Retention of all catechins by Caco-2 monolayers was significantly (P <0.05) enhanced by formulation with ascorbic acid supporting the notion that ascorbic acid may also inhibit efflux of catechins back to the intestinal lumen. Similar to in vitro studies, in in vivo experiments GT+AA and GT+S+AA improved bioavailability of digestively labile EGC and EGCG compared to GT and GT+S formulation respectively. These data provide evidence that formulation factors impact both digestive recovery and may influence intestinal absorption of catechins from tea beverages in vivo.
Degree
M.S.
Advisors
Ferruzzi, Purdue University.
Subject Area
Nutrition
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