Bioscience Methods 2015, Vol.6, No.2, 1-7
5
anti-oxidant activity (Patel et al., 2010), corroborated
this assumption.
According to the results, a positive correlation of
anti-oxidant activity with phenol content was found.
This correlation suggests that most of the vegetables
which are having high antioxidant activity may also
show high phenolic contents. Although the vegetables
may contain other anti-oxidants such as proteins,
ascorbate and the carotenoids, these do not contribute
significantly to the anti-oxidant activity. Results are
represented graphically in Figure 5, with anti-oxidant
activity correlated significantly and positively with
total phenolics (
r
2
= 0.6947, P < 0.05). The results
indicate that vegetables containing high phenolics may
provide a source of dietary anti-oxidants.
3 Conclusion
The study reported the antioxidant activity and total
phenolic contents of fourteen vegetables. The study
clearly indicates that it is important to measure the
anti-oxidant activity using various radicals and
oxidation systems and to take both phenolic content
and anti-oxidant activity into account while evaluating
the anti-oxidant potential of plant extracts. However,
the model system consisting of β-carotene and linoleic
acid can be used to screen large number of sources for
their anti-oxidant capacity. Furthermore, in order to
realize the health benefits from potential plant sources,
additional information on their dietary intake and
enhancing bioavailability after various processing
operations is required. Currently work is underway in
our laboratory to confirm the anti-oxidant activity of
various fruit and other sources by using other
oxidation systems and lipid models. In addition more
work on optimizing processing and storage conditions
for their maximum stabilization is also under progress.
Phenolic compounds could be a major determinant of
antioxidant potentials of food plants and could
therefore be a natural source of antioxidants and
because Phenolic compounds have been associated
with the health benefits derived from consuming high
levels of vegetables.
Research on polyphenol bioavailability must finally
allow us to correlate polyphenol intakes with one or
several accurate measures of bioavailability (such as
concentrations of key bioactive metabolites in plasma
and tissues) and with potential health effects in
epidemiologic studies. Knowledge of these correlations
must be attained despite the difficulties linked to the
high diversity of polyphenols, their different bio
availabilities, and the high inter individual variability
observed in some metabolic processes, especially
those in which the microflora is involved.
4 Materials and Methods
4.1 Sample preparation
Fourteen vegetables were purchased fresh from different
market. These were cleaned, washed and chopped into
small pieces.
Allium cepa
s,
Allium sativum
,
Brassica
rapa
,
Raphanus sativus
, and other vegetables having
dry skins were processed after removal of their skins.
Only edible portions of vegetables were weighed and
homogenized using a pestle motor.
Ethanol extracts of leaves of leafy vegetables as well
as root extracts was prepared. Phenolic content in
these vegetables (
Beta vulgaris
,
Brassica juncea
,
Chenopodium,
Brassica rapa
,
Raphanus sativus
,
Allium
cepa
,
Allium sativum
, French beans, Pea pods, green
chilies,
Brassica oleracea
,
Brassica oleracea
and
Cucumis sativus
) was measured using Folin–Ciocalteau
procedure. Anti-oxidant activity in these vegetables
was measured using β-carotene bleaching method.
Comparative analysis of anti-oxidant activity and
phenolic content in these vegetables shows positive
relationship.
4.2 Determination of total phenolic content
Folin-Ciocalteu procedure
Total phenols were determined using the Folin-Ciocalteu
reagent (Kaur et al., 2002). Samples (2g) were
homogenized in 80% aqueous ethanol at room
temperature and centrifuged in cold at 10,000 rpm for
15 min and the supernatant was saved. The residue
was re-extracted twice with 80% ethanol and
supernatants were pooled, put into evaporating dishes
and evaporated to dryness at room temperature.
Residue was dissolved in 5 mL of distilled water.
One-hundred microliters of this extract was diluted to
3 mL with water and 0.5 ml of Folin-Ciocalteu
reagent was added. After 3 min, 2 mL of 20% of
sodium carbonate was added and the contents were
mixed thoroughly. The color was developed and
absorbance measured at 650 nm in spectrophotometer
after 60 min using catechol as a standard. The results
were expressed as mg catechol/100 g of fresh weight
material.
