Oxidative damage can result when the critical balance between
free radical generation and antioxidant defenses is unfavorable. These
oxidative damages could be retarded by endogenous defense systems
(antioxidant) such as superoxide dismutase (SOD) and catalase (CAT)
which work in concert to detoxify free radicals (Edziri et al., 2012).
Diabetes mellitus is associated with increased oxidative stress and
decreased antioxidant status (Marica et al., 2005). As showed in
Table 3, the activity of SOD was significantly decreased in alloxantreated
rats in the serum, liver and pancreas when compared to the
control (p b 0.05). Similar to that of SOD, the activity of CAT was
also significantly decreased in the pancreas (p b 0.05, Table 4), but
such effect was not observed in the serum and liver (although there
was a decrease in the activity of the enzymes). The decreased levels
of CAT and SOD observed in diabetic rat can be explained by the accumulation
of superoxide anion and hydrogen peroxide respectively,
which would have otherwise been effectively scavenged by these
enzymes. According to the results obtained, the levels of SOD and
CAT were significantly restored after saponin treatment, suggesting
that saponins have effective antioxidative properties and could scavenge
excess free radicals (p b 0.05, Tables 3 and 4). The increased
activities of SOD and CAT suggest a compensatory response to oxidative
stress as it reduces the endogenous hydrogen peroxide produced,
thus, diminishing the toxic effects due to this radical or other free radicals
derived from secondary reactions (Sharma and Garg, 2009).
Consequently, saponin may have an efficient protective mechanism
in response to ROS which may help to regenerate β-cells and protect
pancreatic islets against cytotoxic effects of alloxan