Samples were homogenized, transferred to a 50 ml
volumetric flask, and extracted for 13 h under refrigeration in the
dark. After this period, the extracts were filtered (Whatman No. 1
filter paper) and absorbance at 535 nm (anthocyanins) and
374 nm (yellow flavonoids) were measured in a Shimadzu UV-1800 spectrophotometer (Columbia, MA).