Among the various compounds with functional properties, antioxidants are among the most
researched, as interest in new, safe and effective antioxidants from natural sources is growing
nowadays. Most of the natural antioxidants used in the cosmetic industry are derived from
terrestrial plants, but algae have shown potential as an alternative source of antioxidants.
One such source is the alga Dunalliela sp., which is known to produce betacarotene, a
substance with antioxidant activity.
In the framework of the thesis, the antioxidant efficacy of algal extract of Dunalliela sp. was
evaluated. Two in vitro methods were used, namely diphenylpicrylhydrazyl (DPPH) and
ferricyanocyanate (FTC). For the determination of the antioxidant efficacy by the DPPH
method, we had to first develop a suitable method, as no data were available on the efficacy
of the algal extract. Several methanol and buffer solutions were prepared, the most effective
of which was a solution of the algae in 5 mL of 0.2M phosphate buffer at pH 7. The extract
of Dunalliela sp. was shown to be antioxidant effective. The results of the algae solution
were more comparable with the 0,01 % vitamin E solution and the 0,003 % resveratrol
solution. In the FTC method, 20 % and 40 % algal extract solutions were incorporated into
the linoleic acid emulsion, which was prepared by dissolving the algal extract in 5 ml of 0.2
M phosphate buffer. Both concentrations were able be to inhibit lipid peroxidation, but the
antioxidant activity was more pronounced in the emulsion containing 40 % algal extract.
When compared with the reference antioxidants, we found that the kinetics of the reaction
in the presence of the algal extract solution was different from that of the other antioxidants.
The antioxidant efficacy of the algal extract increased with the irradiation time of the
samples, whereas the conventional antioxidants were most effective during the first two
hours of irradiation of the samples. After eight hours, the tested concentrations of
antioxidants and algal extract showed comparable antioxidant protection. In our thesis, we
found that the algal extract of Dunalliela sp. has antioxidant activity, but this is not as strong
as that of some other antioxidants. Dunalliela sp. extract could be used in cosmetic products
in combination with other antioxidants, where Dunalliela sp. would play the role of cosmetic
active ingredient, while other antioxidants incorporated would ensure the oxidative stability
of the product.
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