2.4. Determination of total phenolic content
The total phenolic concentration was measured using
the Folin-Ciocalteu method (Singleton & Rossi, 1965).
In this procedure, 1 ml of appropriately diluted samples
and a standard solution of gallic acid were added to a
25 ml volumetric flask containing 9 ml of double distilled
water. A reagent blank using double distilled water was
prepared. One milliliter of Folin-Ciocalteu phenol
reagent was added to the mixture and shaken. After
5 min, 10 ml of a 7% sodium carbonate solution was
added with mixing. The solution was then immediately
diluted to a volume of 25 ml with double distilled water
and mixed thoroughly. After incubation for 90 min at
room temperature, the absorbance at 765 nm was measured.
The total phenolic contents of the samples are
expressed in milligrams per serving of gallic acid equivalents
(GAE).