In the previous study showed that the aqueous
extract of C. nervosum contained total phenolicconpounds 181.16 ± 0.59 mg gallic acid equivalences
per 100 gram fresh weight and total flavonoids
54.86 ± 3.45 mg catechin equivalences
per 100 gram fresh weight.8 The phenolic compounds
found in aqueous extract of C. nervosum
might take a part of its antioxidant capacity. The
mechanism of antioxidant activity of C. nervosum
might be involved in scavenging free radical and/
or chelating iron generating Fenton reaction.8
Lipid peroxidation and antioxidant systems were
used as important biomarkers for detection of
antioxidant property of aqueous extract. Four
antioxidant systems (GSH, GPx, CAT and HO-1)
and MDA formation were evaluated for oxidative
status. The results in the present study have
demonstrated that aqueous extract of C. nervosum
could affect both of antioxidant system and
MDA formation in rat liver. It showed that oxidative
stress significantly increased in rats treated
with aqueous extract at a low dose (100 mg/kg
bw). The increasing of oxidative stress in liver
was observed in only rat received low dose of C.
nervosum extract which might be a dose of
prooxidant. Phenolic phytochemicals are not only
recognized as antioxidants, but they can also exert
prooxidant activities. In fact, most free-radical
scavengers act in oxidation–reduction reactions
that are reversible, and some, such as phenolic
phytochemicals, can act both as antioxidants and
prooxidants depending on their structure and the
conditions. The prooxidant activity is thought to
be directly proportional to the total number of hydroxyl
groups.1 4 So, C. nervosum might exhibit
an antioxidant activity at high dosage while act as
a prooxidant at low dosage.
Glutathione is one of the most abundant nonenzymatic
biological antioxidants present in the
liver. Its functions include removal of free radicals
such as hydrogen peroxide, superoxide anions
and alkoxy radicals, maintenance of membrane
protein thiols and acting as a substrate for
glutathione peroxidase (GPx). GPx catalyses the
reduction of H2 O2 and hydroperoxides to nontoxic
products. CAT catalyses the reduction of
H2O2 and protects the tissue from highly reactive
oxygen free radicals and hydroxyl radicals. The
result showed that aqueous extract of C. nervosum
did not affect on total glutathione, glutathione
peroxidase and catalase activities. Other antioxidant
enzyme which determined in the study isheme oxygenase (HO-1). It mediated cytoprotection
which is important for tissues that are vulnerable
to oxidative stress.1 5 Aqueous extract at
dosage of 500 mg/kg bw significantly increased
heme oxygenase activity and also decreased
MDA formation. Although at low dosage of C.
nervosum extract enhance oxidative stress in rat
liver, on the other hand at high dosage of C. nervosum
extract might be able to reduce oxidative
stress by enhancement of non-glutathione pathway
such as heme oxygenase. In conclusion, the
aqueous extract from C. nervosum might show
biphasic effect on oxidative stress in rat liver.