The concentration of phenolic compounds in GSE and
BB was determined by the Folin-Ciocalteau method as
described by Singleton and Rossi (1965). GSE and BB were
dissolved in distilled water, and to 1 ml of sample, 5 ml of
Folin-Ciocalteau reagent (diluted 1:10 with distilled water)
was added. After 5 mins, 4 ml of a sodium carbonate solution
(7.5%) was added to each tube. The tubes were incubated
for 2 h at room temperature and the absorbance
determined spectrophotometrically (DU 640 UV/Vis
spectrophotometer, Beckman Coulter, CA, USA) against
a reagent blank at 740 nm. The total polyphenol content
was calculated using gallic acid as a standard and results
were expressed as gallic acid equivalents (GAE) (g GAE/
100 g extract).