2.5. Measurement of antioxidant activity
DPPH free radical scavenging activity was determined following
procedures described by Bafna and Mishra (2005).
Lipid-peroxidation test was performed following the methods of
Houghton et al. (1995) and Burits and Bucar (2000) using liposomal
suspension from type VII folch bovine brain extract and
thiobarbituric acid reactive substance (TBARS). Trichloroacetic acid
and 2,6-di-t-butyl-p-kresol were also used to precipitate interfering
substances. Total phenolic contents of the plant extracts
were determined using the Folin-Ciocalteau reagent following the
method described by Lowry et al. (1951). Troloxฎ (Fluka): a standard
vitamin E analogue and quercetin (Sigma) were used as
positive controls for DPPH and lipid-peroxidation tests. Caffeic
acid (Sigma) was used as a standard control for phenolic content
test.