Chemistry Reference
In-Depth Information
5.3. Metal chelating effect
It has been proposed that transition metals catalyse the formation of the first few radicals to
start the propagation of radical chain reaction in lipid peroxidation. Chelating agents may
inhibit lipid oxidation by stabilizing transition metals. Ferrozine can quantitatively form
complexes with Fe
2+
. In the presence of other chelating agents, the complex formation is
disrupted with the result that the red colour of the complex is decreased. As shown in
Figure 1B, the ferrozine - Fe
2+
complex is not complete in presence of the plant extract,
indicating its ability to chelate the iron. The absorbance of ferrozine-Fe
2+
complex decreased
linearly in a dose dependent manner (100- 2000g/l) and the IC
50
value is estimated as 2.47
g. The metal chelating activity of
E. agallocha
was evaluated against Fe
2+
. The standard
compounds ascorbic acid and BHT did not exhibit any metal chelating activity at the tested
concentrations (100-2000 g/l). Reaction of ascorbic acid and gallic acid with FeCl
2
might
enhance the degradation of ascorbic acid and gallic acid, and increase the ascorbyl and gallic
acid radical concentrations [17].
5.4. Nitric oxide radical inhibition activity
The antioxidant system protects the pathogens against the ROS-induced oxidative damage.
Nitric oxide radical generated from the sodium nitropruside is measured by the Greiss
reduction. Sodium nitropruside at physiological pH spontaneously generates nitric oxide,
which thereby interacts with oxygen to produce nitrate ions that can be estimated using
Greiss reagents. Thus, the scavengers of nitric oxide compete with the oxygen, leading to
reduced production of nitric oxide. The chromophore formed during diazotization of nitrite
with sulphanilamide and its subsequent coupling with naphthyl ethylene diamine was read
at 546 nm. The methanolic leaf extract of
E. agallocha
has shown a more significant effect
than that of ascorbic acid and the results are explained in Figure 1C. The IC
50
of
E. agallocha
is
estimated as
4.8 g/l.
5.5. Lipid peroxidation and thiobarbituric acid reaction
Egg yolk lipids undergo rapid non-enzymatic peroxidation when incubated in the presence
of ferrous sulphate with subsequent formation of malonodialdehyde (MDA) and other
aldehydes that form pink chromogen with TBA absorbing at 532 nm [18]. Peroxidation of
lipids has been shown to be the cumulative effect of reactive oxygen species, which disturb
the assembly of the membrane causing changes in fluidity and permeability, alterations of
ion transport and inhibition of metabolic processes [19]. The extract of
E. agallocha
exhibited
strong lipid peroxidation inhibition in a concentration dependent manner (Figure 1D). The
IC
50
value for the inhibition of lipid peroxidation is observed to be 100 g/l. This activity
was higher than that of ethanolic and hexane extract of
Ziziphus mauratiana
and
Z. spina-
christi
reported using egg yolk as media of peroxidation [20]. The studies made on
E.
agallocha
leaf extract suggest that it could play a role in protecting the physicochemical
properties of membrane bilayers from free-radical induced severe cellular dysfunction.
