method, 1 ml of tea extract diluted 10–75 times with
deionized water (to obtain absorbance in the range of
the prepared calibration curve) was mixed with 1 ml of
3-fold-diluted Folin–Ciocalteu phenol reagent. Two milliliter
of 35% sodium carbonate solution is added to the
mixture, shaken thoroughly and diluted to 6 ml by adding
2 ml of water. The mixture is allowed to stand for 30
min and blue color formed is measured at 700 nm using
a spectrophotometer