Antioxidant activity in selected local vegetables / Sumathi a/p Murti
A free radical is any atom or molecule that has a single unpaired electron in an outer shell and its damage is closely associated with oxidative damage. Oxidative damage by free radicals in the human body plays an important causative role in disease initiation and progression. Antioxidants pro...
| Summary: | A free radical is any atom or molecule that has a single unpaired electron in an outer
shell and its damage is closely associated with oxidative damage. Oxidative damage by
free radicals in the human body plays an important causative role in disease initiation
and progression. Antioxidants provide a measure of protection that slows the process of
oxidative damage. In this study, crude petroleum benzene, chloroform, methanol and
water extracts of Allium tuberosum (garlic chives), Apium graveolens (L.) (celery),
Ipomoea batatas (L.) (sweet potato leaves), Murraya koenigii (L.) (curry leaves),
Psophocarpus tetragonolobus (winged bean), and Sauropus androgynus (sweet leaves)
were evaluated for antioxidant properties using bioassays namely 1,1-diphenyl-2-
picrylhydrazyl (DPPH) radical scavenging assay, reducing power assay, metal chelating
assay, haemolysate catalytic activity and lipid hydroperoxide assay. In the DPPH assay,
petroleum benzene and chloroform extract of Murraya koenigii showed good free
radical scavenging activities (IC50 = 21.5 µg/ml and 22.5 µg/ml respectively) when
compared with standard ascorbic acid (IC50 = 3.75 µg/ml). IC50 is the concentration at
which 50% of DPPH radicals are inhibited. In the reducing power assay, chloroform
extract of Murraya koenigii showed strong reducing powers with absorbance value of
1.833 ± 0.003 when compared with standard butylated hydroxyanisole (BHA) with
absorbance value of 2.625 ± 0.004 at 1 mg/ml. In the metal chelating assay, methanol
extract of Murraya koenigii showed the highest metal chelating capacity of 88.60 ±
0.20% at 1 mg/ml when compared to ethylenediaminetetraacetic acid (EDTA) which
was 98.63 ± 0.13%. In the haemolysate catalytic activity, water and chloroform extract
of Psophocarpus tetragonolobus; methanol and chloroform extract of Ipomoea batatas;
and chloroform extract of Murraya koenigii showed strong H2
O2 reducing activities of
98.00 ± 0.16%, 92.53 ± 0.99%, 94.03 ± 0.18%, 90.79 ± 0.71% and 87.36 ± 0.77%
respectively at 200 µg/ml while the standard absorbance by unblocked catalase is 99.95 (0.949) ± 0.02%. In the lipid hydroperoxide assay, methanol extract of Ipomoea batatas
showed highest hydroperoxide value of 3.079 nmol whereas methanol extract of Apium
graveolens showed lowest hydroperoxide value of 0.329 nmol at 25 nmol in comparison
with hydroperoxide value of the lipid hydroperoxide standard which was 4.839 nmol
obtained at 5 nmol. Thin layer chromatography (TLC) were carried out on four active
crude extracts namely crude chloroform and petroleum benzene extract of Murraya
koenigii, crude water extract of Psophocarpus tetragonolobus and Apium graveolens to
screen secondary compounds present through different type of visualisation. A spot
under shortwave UV light and iodine vapour visualisation, orange colour deposition in
Dragendorff’s reagent test and pink colour spot on TLC plate from sulphuric acid
visualisation in all four active crude extracts indicates the presence of organic
compounds, unsaturated carbon bonds, alkaloid compounds and oxidisable components,
respectively. The presence of these organic compounds, unsaturated carbon bonds,
alkaloid compounds and oxidisable component found in the selected vegetables may be
linked to the high anti-oxidative activities observed; hence its dietary consumption may
be beneficial for general health as well as disease prevention. |
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