Briefly, the 0.5 mL of extract was mixed with 4 mL distilled water, than 0.3 mL 5% NaNO2 was added and allowed to react for 5 min. Following this, 0.3 mL 10% AlCl3 was added and the mixture was allowed to react for a further 5 min. At the end, 2 mL 1 M Na2CO3 and 2.4 mL distilled water were added to the reaction mixture and the absorbance at 510 nm was read against a blank.