2.6. Total phenolic content
The amount of total soluble phenolics was determined according to the Folin–Ciocalteu method (Gutfinger, 1981). The reaction mixture was consisted of
0.5 ml of the extract (1.5–15 mg/ml, depending on the
activity), 5 ml of distilled water, 0.5 ml of the Folin–Ciocalteu s reagent. After a period of 3 min, 1 ml of saturated sodium carbonate solution was added. The 10 ml
volumetric flasks were shaken and allowed to stand for
1 h. The absorbance was measured at 725 nm (each measurement repeated three times) in a Shimadzu UV–Vis-
160A spectrophotometer (the same equipment was used
in the DPPH test). The total phenolic content was expressed as mg gallic acid/g dry extract, mg gallic acid/
100 g dry peel.