Influence of solvent extraction on antioxidant activity of ...
Transcript of Influence of solvent extraction on antioxidant activity of ...
MATERIALS ANDMETHODS RESULTS
Antioxidant activity averaged over all extraction times and
solvent:waste ratios was significantly different (p<0.05) between
solvents, with 50% acetone demonstrating higher yield. (Table 1).
The 0.01% pectinase and petroleum ether solvents were
significantly less effective for extracting antioxidant compounds.
Therefore only the antioxidant activity of 50% acetone and 70%
methanol extracts will be presented (Fig. 5).
Influence of solvent extraction on antioxidant activity of Cynthiana grape
pomace using Oxygen Radical Absorbance Capacity (ORAC) assay
Ioannis P. Oikonomakos, Akhila Vasan, William McGlynn and Christina A. Mireles DeWitt
Robert M. Kerr Food & Agricultural Products Center, Oklahoma State University, Stillwater, OK, 74078
Industrial waste streams from horticultural processing may be a potential
source for dietary antioxidants. Our study focused on developing a rapid
and scalable method for screening winery waste for antioxidant activity
using different combinations of solvent extractions.
Our results showed that all extracts had antioxidant activity. Extraction
efficiency was significantly different (p<0.05) among all solvents. Higher
activity was observed in the 50% Acetone (27-37µmoles Trolox
equivalents/g pomace) and 70% Methanol extracts (17-24µmoles Trolox
equivalents/g pomace). The antioxidant activities of petroleum ether and
pectinase/water extracts were much lower, at 2 and 5µmoles Trolox
equivalents/g pomace respectively. For all solvents, 8h of extraction at 4:1
solvent to sample ratio showed the highest activity.
ABSTRACT
Fig. 1. Cynthiana (=‘Norton’)
Grape pomace from cultivar Cynthiana (Vitis aestivalis) (Fig.1)
Screening
Liquid N2
Grinding 4oC
Storage -20oC
Sample Preparation
Fig. 2. Extraction
Table 1. Average antioxidant activity of Cynthiana extracts.
Solvent
Average Activity
(µmoles TE/gr tissue)
50% Acetone 32a
70% Methanol 21b
0.01% Pectinase 5c
Petroleum Ether 2d
ACKOWLEDGEMENTS
For all solvent ratios and shaking times, the 50% acetone showed
significantly (p<0.05) higher antioxidant activity than the 70%
methanol extracts. Highest yields were obtained at 8h shaking and
4:1 solvent:waste, with ≈37µmoles TE/g tissue for the 50%
acetone and ≈24µmoles TE/g tissue for the 70% methanol (Fig. 5).
Fig. 4. Plate reader
Overall, our screening method allowed us to identify potentially high-value
grape processing waste products, thus paving the way toward developing a
commercially-viable method for extracting antioxidants from grape pomace.
• 50% acetone
• 70% methanol
• Water + 0.01% pectinase
• Petroleum ether
Solvent : Pomace
2:1 & 4:1
Extraction time (h)
1, 2, 4, 8Vacuum
Filtration
Solvent
Adjustment
Solvent
Treatment
Storage -20oC
Sample Extraction
Fig.3
ORAC Assay Fig. 4
Sample AnalysisFig. 3. Sample filtration
Fig. 2. Extraction
Fig. 2
Results were expressed as
Equivalent µmoles of Trolox per
gram tissue (TE/g tissue).
CONCLUSIONS
• Our study indicates that Cynthiana grape pomace has a significant
amount of antioxidants (Table 2), and could be extracted as part of an
industrial waste utilization system.
• 50% acetone is an effective solvent to extract these antioxidants with
satisfactory yields even at lower solvent:pomace ratio and extraction
times, suggesting that the majority of the solvent’s extraction potential
can be achieved using half the volume and time of the maximum yield.
This may prove to be more economical for screening studies.
Petroleum Ether 2
a Numbers with different letters denote significance at p<0.05
Activity shown is an average across all shaking levels and ratios of solvent
Fig. 5. Average antioxidant activity of 50% acetone and 70% methanol extracts
Table 2. Antioxidant activity from different food sources
Food Source/products
Total ORAC
(μmoles TE/ 100 gr tissue)
Blackberries, raw 5347
Blueberries, raw 6552
Grapes, red, raw 1260
Grapes, white or green, raw 1118
Grape juice, white 793
Grape juice, red 1788
Tomatoes, raw and cooked 367-694
Cynthiana pomace ≈2000-4000
Values obtained from USDA 'ORAC of selected foods - 2007'
• Future research will be
focused on identifying the
antioxidant compounds in
grape pomace and
screening for antioxidants
at different steps of wine
production.Oklahoma State University
Agricultural Experiment Station
Robert M. Kerr
Food and Agricultural Product Center
Oklahoma State University
Department of
Horticulture & Landscape Architecture