Degradation ofb-carotene was determined by the method of
Chewet al.[19], with minor modifications. There were added
2.5 mgb-carotene and 40 mg linoleic acid, both solubilized
in chloroform, to 400 mg Tween 40 emulsifier. In a rotary
evaporator, the chloroform was evaporated and 100 mL
oxygen-saturated ultrapure water (Milli-Q) was added. Then,
the mixture was vigorously stirred to form an emulsion; 3 mL
of this emulsion was mixed with 1 mL algal extracts at
different concentrations (7.81–1000mg/mL) and the initial
absorbance was read at 470 nm. The tubes were incubated at
50
C for 3 h and, after that, the absorbance was read again at
the same wavelength; the two readings were made in a
microplate reader (Biochrom Asys UVM 340). The BHA was
used as positive control at the same concentrations of algal
extracts. The antioxidant activity was calculated according
to Eq. (3).