Total phenolic content of extract was measured using a modified Folin-Ciocalteu procedure [25 (link)]. In brief, 100 μl of various concentrations of extract were mixed with 1.0 ml of Folin–Ciocalteu reagent (previously diluted 10-fold with distilled water). After 5 min, 1.0 ml of 7.5 % sodium bicarbonate solution was added to the mixture and allowed to stand for 90 min at room temperature in the dark. The absorbance of the mixture was measured at 725 nm. A calibration curve was prepared using a standard solution of gallic acid and the total phenolic content was expressed as mg gallic acid equivalents pergram of extract (mg GAE/ g extract).
The flavonoid content was determined according to method of Hatamnia with a minor modification [26 (link)]. Briefly, 50 μl of sodium nitrate solution (5 %) was added to 500 μl of the extracts and allowed to react for 5 min. Then 50 μl of 10 % aluminum chloride solution was added. Finally, 250 μl of 4 % sodium hydroxide solution was added into the mixture 5 min later. The absorbance of the mixture was immediately recorded at 518 nm. A calibration curve was prepared using a standard solution of rutin and the total flavonoid content was expressed as mg of rutin equivalents pergram of extract (mg RU/ g extract).
The flavonoid content was determined according to method of Hatamnia with a minor modification [26 (link)]. Briefly, 50 μl of sodium nitrate solution (5 %) was added to 500 μl of the extracts and allowed to react for 5 min. Then 50 μl of 10 % aluminum chloride solution was added. Finally, 250 μl of 4 % sodium hydroxide solution was added into the mixture 5 min later. The absorbance of the mixture was immediately recorded at 518 nm. A calibration curve was prepared using a standard solution of rutin and the total flavonoid content was expressed as mg of rutin equivalents pergram of extract (mg RU/ g extract).
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