2.2. Estimation of total phenol and flavonoid content in FPP
The methods described in Singleton et al. (2003) and Zhishen et al. (1999) were
adapted and used for the quantification of total phenols and total flavonoids in FPP.
Briefly a known concentration of FPP was added to 3.5 ml of distilled water, 250 ll
of Folin–ciocalteau reagent and 1 ml 20% (w/v) sodium carbonate. The reaction
mixture was incubated at 40 C for 40 min and optical density (OD) read at
685 nm (Genesys™ 10S, Thermo Scientific, USA). For the quantification of total
flavonoids: to 500 ll FPP, 150 ll 5% (w/v) sodium nitrite and 2 ml of distilled water
were added. After 5 min, 150 ll 10% (w/v) aluminum chloride and 1 ml (1 M) sodium
chloride was added and final volume topped up to 5 ml with distilled water.
The OD was read at 510 nm (Genesys™ 10S, Thermo Scientific, USA). Estimation of
total phenol and flavonoid content was calculated using the formula (adapted from
Sharma et al. (2011)):