Flavonoid content was determined according to methods
described by González-Aguilar, Villegas-Ochoa, Martínez-Téllez,
Gardea, and Ayala-Zavala (2007). 1 mL from each extracted sample
was mixed and equilibrated with 4 mL of deionized water and
300 lL 5% NaNO2 for 5 min. After equilibrium, 300 lL of 10% AlCl3
(methanolic solution) were added; the mixture was allowed to sit
for 1 min and then 2 mL of 1 M NaOH were added. The last volume
was completed to 10 mL with H2O, stirred, and readings were
taken. Mixture absorbance was determined at 415 nm, using a
UV–Vis spectrophotometer PerkinElmer Lambda 11. Concentration
of total flavonoids of fruits was calculated using a standard curve of
quercetin (0–60 ppm) and expressed as mg quercetin equivalents
(QEs)/100 g of DW.