Effect of heat treatments on total phenols, flavonoids and antioxidant activity of Clove (Syzygium aromaticum L.) and Turmeric (Curcuma longa L.)
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Date
2015
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Publisher
CCSHAU
Abstract
The present study was undertaken to study the effect of heat treatments on phytoconstituents and
antioxidant activities of clove buds and turmeric rhizomes powder of var. BSR-2 and germplasm material.
Seven heat treatments (100°C for 15, 30 & 45 min., 110°C for 15, 30 & 45 min. and no heat treatment)
were given to clove buds and turmeric rhizomes powder. All the samples in triplicate were extracted using
three solvents viz. acetone, ethanol and water. It was observed that total phenols (mg GAE/g) and
flavonoids (mg CE/g) content, DPPH free radical scavenging activity (%) and antioxidant activity (%) in
clove buds and turmeric rhizomes samples increased significantly with increase in temperature of heat
treatments (i.e. 100°C and 110°C) in comparison to samples with no heat treatment. In clove buds
samples, the percent increase in total phenols & flavonoids content, DPPH free radical scavenging
activity (%) and antioxidant activity (%) was 2.97 to 11.30, 5.50 to 16.51, 0.17 to 4.38 and 1.50 to 6.23,
respectively after heat treatments. Similarly in turmeric rhizomes samples, the percent increase in total
phenols & flavonoids content, DPPH free radical scavenging activity (%) and antioxidant activity (%)
was 10.75 to 32.04, 5.08 to 13.50, 0.46 to 26.11 and 1.77 to 7.48, respectively after heat treatments. It was
also observed that total phenols & flavonoids content, DPPH free radical scavenging activity (%) and
antioxidant activity (%) increased significantly with increase in heating time from 15 to 30 minutes and
finally to 45 minutes at both temperatures i.e. 100°C & 110°C. Contrary to total phenols and flavonoids
content, total sugars (mg/g), reducing sugars (mg/g), non-reducing sugars (mg/g) and curcumin (g/100g,
in turmeric only) contents in clove buds and turmeric rhizomes samples decreased significantly with
increase in temperature of heat treatments (i.e. 100°C and 110°C) and heating time (from 15 to 30
minutes and finally to 45 minutes at both temperatures) in comparison to samples with no heat treatments.
In clove buds samples, the percent decrease in total sugars, reducing sugars and non-reducing sugars was
4.62 to 25.06, 4.42 to 24.80 and 20.83 to 50.00, respectively after heat treatments. Similarly in turmeric
rhizomes samples, the percent decrease in total sugars, reducing sugars, non-reducing sugars, and
curcumin (in turmeric only) contents was 7.81 to 31.17, 7.95 to 45.90, 6.70 to 26.56 and 5.21 to 27.06,
respectively after heat treatments. Amongst solvents, total phenols, DPPH free radical scavenging activity
and antioxidant activity in clove buds were highest in water extracts whereas in turmeric rhizomes these
parameters and curcumin contents were highest in acetone extracts. In clove buds & turmeric rhizomes,
flavonoids and sugars contents were highest in acetone and water extracts, respectively. Thus,
phytoconstituents and antioxidant activity of clove buds and turmeric rhizomes were affected due to
various heat treatments and solvent polarity.
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Keywords
extraction, turmeric, antioxidants, sampling, cloves, phenols, aromatic compounds, irrigation, alcohols, solvents