The sample extract of 15 g was dissolved in water and the
volume was made up to 100 ml with distilled water. 5 ml of this
aliquot was taken and 0.3 ml of NaNO2 (5%) was added, kept
for 5 min followed by addition of 0.3 ml of AlCl3 (10%), againkept for 6 min followed by addition of 2 ml sodium hydroxide
(1 N) solution. Volume was made up to 10 ml with distilled
water and absorbance was measured at 510 nm by spectrophotometer
(Shimadzu 1609, Tokyo, Japan) using catechin as
standard and distilled water as blank (Zhishen, Mengcheng, &
Jianming, 1999).