HPLC analyzes have demonstrated that the major carotenoid
presented in the muscles of shrimp is astaxanthin, as a freer ester-compound; corresponding to 75% of the total
carotenoids in both CS and SS groups (data not shown).
Nevertheless, it was verified that CG possess 2.82 mg of
astaxanthin/kg of muscle shrimp, while SS presented
4.55 mg of astaxanthin/kg of shrimp. These results demon-strate that even considering small quantities of other car-otenoids presented in the original chow furnished to the
shrimp (control group— CS), those carotenoids were able to
convert carotenoids traces into astaxanthin. On the other
hand, it was clear chow supplemented with the H. pluvialis
algae yielded shrimp with higher content of astaxanthin.
Furthermore, such a high astaxanthin content was respon-sible for the increased in vitro antioxidant activity observed
for the carotenoids extract of the SS group in comparison to
the control group.
The results show the ability of shrimp total carotenoids in
preventing lipid peroxidation in the serum and liver of rats.
Fig. 1 shows the determination of the TBARS levels after the
induction of lipid peroxidation, in the rat serum and liver,
using CuCl 2 ( Fig. 1) and AAPH ( Fig. 2 ) as the oxidant agents.
Considering the data from serum ( Fig. 1A), it is observed that
the carotenoids of the SS group presented a protective and
concentration-dependent effect against lipid peroxidation,
which was statistically similar to that of the synthetic
astaxanthin ( P 40.05). However, the total carotenoids of the
CS group was lower when compared with synthetic astax-anthin ( P o0.05). Total carotenoids of the SS group also
demonstrated a protective and concentration-dependent
effect against the liver lipid peroxidation, but only at the
highest concentrations studied (2.5 and 5 μM) the effect was
statistically comparable to synthetic astaxanthin ( Figs. 1 and
2B). Similarly to the serum lipid peroxidation results, the total
carotenoids of the CS, was statistically lower when compared
to synthetic astaxanthin.
To the best of our knowledge, no study has described the
β-carotene/linoleic acid co-oxidation technique in order to
determine the antioxidant activity of astaxanthin. Therefore,
with the method proposed by Marco (1968) and modifi ed by
Miller (1971) it was possible to achieve the standardisation of
this technique for the utilization of carotenoids extracted
from muscle shrimp. The results showed that total carote-noids of the SS group had an antioxidant ability similar
to that of the synthetic astaxanthin ( Fig. 3). On the other
hand, it was that 10 or 20 μM carotenoids of the CS group
did not demonstrate antioxidant activity different from the
astaxanthin group.
The ability of carotenoids to scavenge the free radical
DPPH, expressed as percentage of DPPH scavenging, is
demonstrated in Fig. 4. It is demonstrated that total carote-noids extracted from the muscles of shrimp presented an
antioxidant profile similar to the synthetic astaxantin, i.e. the
higher the concentration of total carotenoids the greater the
ability to scavenge the free radical DPPH. It can be observed
that the highest concentration of astaxanthin evaluated, i.e.
10 μM, induced a greater inhibition for both groups tested
(SS and CS), suggesting a possible concentration-dependent
effect.
Similar results were observed by Sachindra and Bhaskar
(2008) when investigating the in vitro antioxidant activity of
the products extracted from shrimp residues and by Rao,
Sarada, Baskaran, and Ravishandar (2006) when studying the
antioxidant activity of a carotenoid extract of the algae
Botryococcus brauni. Santos et al. (2012) obtained promising
results concerning antioxidant and antiinfl amatory activity of
L. vannamei extracts residues. Here, once again, the antiox-idant ability of the total carotenoids of the SS group was
closer to that of the synthetic astaxanthin and the effects of
both carotenoids were higher than that of the CS group
( P o0.05; Fig. 4). According to Gordon (1990), the antioxidant
activity is based on the cleavage of the free radical chain by
the donation of one hydrogen atom. Considering such a
hypothesis, it is believed that the carotenoids presented in
the extract, including astaxanthin, might donate hydrogen
atoms of the phenolic hydroxyl groups to the free radical.
Accordingly, it can be inferred that the carotenoids present in
the shrimp may be able to form a stable final product
incapable of disseminating future oxidative reactions.
In summary, the results presented herein, considering the
antioxidant activity of total carotenoids extracted from
shrimp, corroborate the results of several in vitro studies that