People in Bangladesh are traditionally used to consume mainly black tea. However, some
tea manufacturing companies are now producing green tea, though in a small scale. To
create new knowledge as well as awareness about the consumption of green tea, the
present study was carried out to compare the black and green tea available in Bangladesh
based on their bioactive compounds and antioxidant activity. A total of eight brands of
black tea and two brands of green tea were bought from the supermarkets. Total phenolics,
total tannin, total flavonoids, and caffeine content were measured as bioactive compounds,
and antioxidant activity was evaluated by using two different methods such as DPPH (1,1-
diphenyl-2-picrylhydrazyl) radical-scavenging activity and ABTS+ radical scavenging
activity of methanol extracts of black and green tea. Every bioactive compound in black
and green tea was found to be significantly different (P < 0.05). The total phenolic
content, on average, was measured at 242.46 mg GAE/g dry extract and 763.41 mg GAE/
g dry extract in black and green tea, respectively. Black tea contained 6.47 mg TAE/g dry
extract tannin, whereas green tea had much more tannin content, 14.51 mg TAE/g dry
extract, which is more than double in amount. On the other hand, the total flavonoid
content was almost double in black tea (61.82 mg QE/g dry extract) compared to green tea
(31.85 mg QE/g dry extract). Antioxidant activities were determined at different
concentrations of tea samples. At every concentration, green tea presented higher ABTS+
and DPPH radical scavenging activity than black tea. The highest percentage of inhibition
was observed at 20 ppm both in black and green tea, finding 98.50 % and 99.07 %
inhibition, respectively. Overall, significantly (P < 0.05) higher amount of phenolic
compounds as well as antioxidant activity were observed in green tea.
A Randomized Controlled Trial of Green Tea Beverages on the in vivo Radical Scavenging Activity in Human Skin