Factors affecting the levels of catechins and caffeine in tea beverage: estimated daily intakes and antioxidant activity

Abstract

Increased public awareness of health benefits of green tea is generally based on the high polyphenol content of tea leaves and the resulting beverage. A number of factors, such as species, season, agronomic condition and age of the leaves, are known to affect the composition of commercial teas. In the present study the effects of factors associated with domestic preparation and analytical methods, such as brewing time, concentration, solvent and type of tea product, on levels of catechins and caffeine, antioxidant activity and estimated daily intakes were investigated. There were large variations in the levels of total catechins: 43 and 117 mg g −1 dry matter (DM) (brewed for 30 s and 5 min respectively); 72 and 161 mg g −1 DM (extracted in boiling water and 50% acetonitrile respectively); 72 and 117 mg g −1 DM (a tea bag and tea leaves respectively). The effects on caffeine content were comparatively smaller. These variations consequently led to considerable variations in estimated daily intakes based on three cups (600 ml), ranging between 538 and 2014 mg g −1 DM of total catechins and between 103 and 466 mg g −1 DM of caffeine. The antioxidant activity was highest (26 680 µmol g −1 DM) for tea leaves brewed for 5 min and lowest (10 110 µmol g −1 DM) for a tea bag product brewed for 1 min.

The role of antioxidant versus pro‐oxidant effects of green tea polyphenols in cancer prevention

“…The green tea phenolic compounds of highest concentration are gallic acid (GA), (−)‐gallocatechin (GC), (+)‐catechin (C), (−)‐epicatechin (EC), (−)‐epigallocatechin (EGC), (−)‐epicatechin gallate (ECG), (−)‐epigallocatechin gallate (EGCG), p ‐coumaroylquinic acid (CA), and (−)‐gallocatechin‐3‐gallate (GCG) (Fig. 1), with EGCG being the most abundant by weight 3, 4. Green tea also contains condensed and hydrolyzable tannins 5.…”

“…The extraction of green tea polyphenols into tea is both time‐ and temperature‐dependent 3, 4. Tea preparation is important, as hot water preparation causes tea to be better at scavenging oxidative radicals than cold water preparations 7, which is likely due to greater extraction of polyphenols.…”

Antioxidant capacity and phenolic composition of fermented Centella asiatica herbal teas

“…C. asiatica herbal tea obtained from the market is prepared by simple drying and is usually mixed with black tea to achieve a more yellow infusion. However, tea is known to contain high caffeine concentration (up to 23.79 g kg −1 )9 and has been reported to bring about adverse effects on human health 10. To avoid the intake of caffeine from tea mixed with C. asiatica herbal tea, fermentation of only C. asiatica leaves may be an alternative method and the process is believed to enhance the quality of herbal tea in terms of colour, flavour and taste 11, 12.…”

Cancer Preventive Effects of Green Tea Polyphenols

“…2 The most abundant polyphenol constituents are gallic acid (GA), (2)-gallocatechin (GC), (1)-catechin (C), (2)-epicatechin (EC), (2)-epigallocatechin (EGC), (2)-epicatechin gallate (ECG), (2)-epigallocatechin gallate (EGCG), p-coumaroylquinic acid (CA), and (2)-gallocatechin-3-gallate (GCG) (Figure 98.1), with EGCG contributing the highest concentrations compared to other GTPs. 3,4 Green tea also contains both condensed and hydrolyzable tannins. 5 Epidemiological studies have shown that green tea consumption is correlated with a lower incidence of many types of cancer, 6,7 yet these correlations are not universal.…”