The antioxidant activity of natural antioxidants
have been attributed to different mechanisms, among which are prevention of
chain initiation, decomposition of peroxides, prevention of continued hydrogen
abstraction, binding of transition metal ion catalysts, reductive capacity and
radical scavenging.There is number of antioxidant methods have
been proposed to evaluate antioxidant activity. The DPPH assay, NO assay, Reducing power assay, metal chelating, active
oxygen species such as H2O2, O2•-
and OH• quenching assays are mainly used for the evaluation of antioxidant
activities of plant extracts [21,22].In
the present paper, we have evaluated the antioxidant activity of different
extracts of Urtica dioica Linn. (UD)
DPPH (1, 1-Diphenyl-2-picrylhydrazyl) is stable
nitrogen centred free radical which can be scavenged by antioxidants and shows
absorbance at 517 nm. DPPH radical accepts an electron or hydrogen radical to
become a stable diamagnetic molecule. The change in absorbance of DPPH radical
caused by antioxidants is due to the reaction between the antioxidant molecules
and the radical, which results in the scavenging of the radical by hydrogen
donation . The ethyl acetate extract showed significant DPPH
scavenging activity Table 2. (IC50 78.99 ± 0.171 µg/ml) and compared
with the standards Ascorbic acid (IC50 26.24 ± 0.193 µg/ml).
Nitric oxide (NO) is a diffusible radical and cause
pathological changes in the cellular structure and functional behavior of
cellular components. It is a diffusible free radical that plays various roles
as an effectors molecule in diverse biological systems, even though nitric
oxide is involved in defence, over production of free radical contributes to
the pathogenesis of various inflammatory diseases [23, 24]. Ethyl
acetate extract of Urtica dioica
Linn. (UD) significantly inhibited NO in a dose dependent manner Table 3 with
the IC50 101.39 ± 0.306µg/ml and it’s compared with the standards
Ascorbic acid having the IC50 values of 55.38 ± 0.560µg/ml.
Phenols are important phytoconstituents because of
their free scavenging ability due to their hydroxyl groups. In various studies
it has been reported that, a highly positive relationship between total phenols
and antioxidant activity was present in several plant species [3, 20].The
polyphenolic compounds were reported to be associated with antioxidant activity
and play an important role in stabilizing lipid peroxidation and also have
inhibitory effects on mutagenesis and carcinogenesis in humans .
The total phenolic contents of the Urtica dioica linn. (UD) different
extracts as gallic acid equivalents were found to be highest in ethyl acetate
extract (13.06±0.15 mg/g). The findings shows that the extent of antioxidant
activity of the all extracts are in accordance with the amount of phenolics
present in that extract. The plant Urtica
dioica Linn. (UD) being rich in phenolics may provide a good source of
Amongst all the extracts, ethyl acetate extracts of Urtica dioica Linn. (UD) showed potent antioxidant potential as
determined by various procedures. The presence of phenolic compounds and
flavonoids in the extracts confirmed their utility as potent antioxidant agent.
We express our sincere thanks to Management and
Shri. Parveen Garg, Honorable Chairman, ISF College of Pharmacy, Moga (Punjab)
for providing necessary facilities.
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