Editor's Note

Green tea has a long history of traditional use, with documented consumption dating back thousands of years in China. Green tea has been investigated for beneficial effects related to a variety of issues including obesity, diabetes, hypertension, dyslipidaemia, and cardiovascular disease, and is currently consumed habitually by millions of humans. Epigallocatechin-3-gallate (EGCG) and L-theanine (LTA) are two of the most abundant constituents in green tea. EGCG has been reported to significantly inhibit weight gain and reduce blood liver cholesterol levels in mice, and LTA has been found to inhibit weight gain and reduce total cholesteroltriglyceride, and free fatty acid levels in the blood of mice. But EGCG is highly sensitive to digestive conditions; clinical and animal studies have shown that the absolute bioavailability of EGCG in plasma is only 0.1%.  Researchers here investigate bioavailability and efficacy of EGCG-LTA complexes with cyclodextrin encapsulating carrier materials through physicochemical characterization, in vitro simulated digestion, and in vivo lipid-lowering weight loss assays. Results suggest increased bioavailability of the EGCG complexes, increased gut micro-diversity and lipid metabolism, and enhanced the lipid-lowering and weight loss effects of EGCG in vivo.
March 2022
Journal of Functional Foods
Abstract

Epigallocatechin-3-gallate (EGCG) and L-theanine (LTA), which are active ingredients in green tea, can inhibit fat accumulation; however, EGCG bioavailability is <5%. Here, we aimed to improve EGCG bioavailability and efficacy by preparing EGCG + LTA/β-cyclodextrin (βCD) inclusion complexes by freeze-drying EGCG + LTA at their mass ratio (5:1) in green tea. Physicochemical characterisation revealed that the supramolecular EGCG + LTA/βCD inclusion complexes had distinct crystal structures formed via intermolecular hydrogen bonding. The inclusion complexes prevented simulated EGCG digestion in vitro while increasing its bioaccessibility and antioxidant activity (p < 0.05). In rats fed a high-fat diet, EGCG + LTA/βCD inclusion complexes significantly increased gut microflora diversity and the abundance of lipid metabolism-related genera but decreased the abundance of EGCG catabolism-related genera. Furthermore, the inclusion complexes significantly enhanced the lipid-lowering and weight loss effects of EGCG in vivo (p < 0.05), likely by improving gut microflora and EGCG bioavailability.
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