The antiradical activity of each extract was evaluated following
a spectrophotometric DPPH method (Thaipong, Boonprakob,
Crosby, Cisneros-Zevallos, & Byrne, 2006). Methanolic solutions
of each extract (3 mL) at varying concentrations (1–5000 lg/mL)
were added to methanolic solution of DPPH (1 mL, 0.1 mM) and
allowed to stand in the dark for 30 min at room temperature. Then
the absorbance of solution was measured at 517 nm (IRMECO
5000) and antioxidant activity was calculated as percentage inhibition
of DPPH free radical using the following equation below;
% reduction ðDPPHÞ ¼ 1 Absorbance sample
Absorbance of DPPH soln 100
the concentration of compound to produce 50% inhibition of DPPH
(IC50) for DPPH free radical scavenging were calculated using linear
regression analysis; IC5 = 50/m.
2