Abstract
Catechins in green tea have various useful features including antioxidant activity and preventive effects on metabolic syndrome. Various beverages that are enriched with tea catechins are marketed as Foods for Specified Health Uses (FOSHU) in Japan. However, recent reports have indicated that excessive consumption of green tea extracts as a dietary supplement are associated with adverse health effects such as liver disorders. Various catechins and caffeine are constituents of FOSHU tea-based beverages. The amount of catechins in FOSHU products is displayed on labels as total catechin content, but the content of individual catechins are not provided. Although health hazards of FOSHU products have rarely been reported, precise information about the content and types of catechins in FOSHU products is needed to ensure safety. We used high-performance liquid chromatography with a photodiode array (HPLC/PDA) to simultaneously identify and quantify catechins and caffeine in green tea-based popular beverages and FOSHU beverages. This technique allowed simultaneous quantitation of five types of catechins and caffeine in green tea without complicated sample preparation. Epigallocatechin gallate (EGCG) and epigallocatechin EGC were the main catechins in various FOSHU beverages and the concentrations of almost all catechins were higher in FOSHU, than in popular green tea-based beverages. The concentrations of EGCG in green tea-based popular beverages and in FOSHU beverages were 5.4 - 7.3 and 10.2 - 41.9 mg/100mL, respectively, with the highest concentration being in a product named Healthya (approximately 147 mg/bottle). The simultaneous determination of compounds such as catechins and caffeine in FOSHU beverages can help to estimate beneficial and adverse effects to prevent deleterious effects on health and the excessive consumption of FOSHU beverages containing high concentrations of tea catechins should be avoided.
Highlights
Tea produced from the leaves of Camellia sinensis is the most common beverage consumed worldwide
Epigallocatechin gallate (EGCG) and epigallocatechin EGC were the main catechins in various FOSHU beverages and the concentrations of almost all catechins were higher in FOSHU, than in popular green tea-based beverages
We simultaneously measured the concentrations of the major catechins EGCG, EGC, EC, ECG, and +C, and caffeine (Figure 1) using a gradient method
Summary
Tea produced from the leaves of Camellia sinensis is the most common beverage consumed worldwide. It is categorized as green, oolong, or black, depending on whether the tea leaves are nonfermented, partially fermented, or completely fermented/oxidized, respectively. Green tea prepared from processed leaves of Camellia sinensis, contains large amounts of polyphenols, most of which are catechins. The major types of catechins in green tea are epigallocatechin gallate (EGCG), epigallocatechin (EGC), epicatechin (EC) and epicatechingallate (ECG), along with their heat-induced isomers that include catechin (+C), gallocatechin (GC), catechingallate (CG), and gallocatechingallate (GCG). EGCG has been extensively investigated since it is the dominant catechin in green tea
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