Extracts obtained by PWE were dried under vacuum at 40 C in
order to prepare precise concentrations of the extracts and then diluted
with distilled water to the target concentrations. The antioxidant
activities of the extracts and synthetic anti-oxidants were
determined by a b-carotene-linoleate model system (Singh et al.,
2002). Briefly, 0.2 mg of b-carotene in 0.2 ml chloroform, 20 mg
of linoleic acid, and 200 mg of Tween-40 (polyoxyethylene sorbitan
monopalmitate) were mixed. Chloroform was removed in vacuum
and nitrogen gas purging at 40 C, and the mixture was
diluted with 10 ml of distilled water and mixed. To this emulsion
40 ml of oxygenated water was added. Four millilitres of this solution
was transferred into a vial containing 0.2 ml of extracts
(200 mg/l) or synthetic anti-oxidants (BHA and BHT) with different
concentration ranges. The vials were placed in a thermostated
waterbath at 50 C. The absorbances of the solutions were measured
at zero time (t = 0) and 15 min intervals until the colour of
b-Carotene disappeared in the control sample (t = 180 min). Control
sample was prepared in the same way using 0.2 ml of water instead
of extracts. Blank was prepared in the same way as explained
above without using b-carotene. The anti-oxidant activity (AA%) of
the test samples was calculated in terms of bleaching of the b-carotene
using the formula given below:
A