5. Total flavonoids
Total flavonoid content was determined by a colorimetric
method (Bao et al., 2005) with minor modification. Aliquots
(0.5 mL) of appropriately diluted extracts or standard solutions
were pipetted into 15-mL polypropylene conical tubes containing
2 mL double distilled H2O and mixed with 0.15 mL 5% NaNO2. After
5 min, 0.15 mL 10% AlCl3$6H2O solution was added, and the mixture
was allowed to stand for another 5 min, and then 1 mL 1 M NaOH
was added. The reaction solution was well mixed, kept for 15 min,
and the absorbance was determined at 415 nm. Total flavonoid
content was calculated using the standard rutin curve, and
expressed as mg rutin equivalent (mg RE) per 100 g of dry weight.