3. FOOD ChEMISTRy & bIOTEChNOLOGy 3.1. Lectures

Chem. Listy, 102, s265–s1311 (2008) Food Chemistry & Biotechnology
P23 ANTIOxIDANT ACTIVITy OF FLAVANOLS
FROM GRAPE SEED ExTRACTS
RUGInA DUMITRITA, SIMOnA VICAS, CARMEn
MOMEU and CARMEn SOCACIU
Univeristy of Agricultural Sciences and Veterinary Medicine,
Cluj-Napoca, Calea Manastur Street, No. 3–5, Romania,
oliviapreda@gmail.com
Introduction
natural antioxidants, particularly from fruits and vegetables,
have gained increased interest among consumers and
scientific community, due to their lower risk for cardiovascular
diseases and cancer demonstrated by many studies 6 .
Grape seeds are a rich source of flavanols, having monomers
such as catechin, epicatechin, epicatechin-3-o gallate
and dimers, trimers, teramers. Extracts from four varieties of
Romanian grapes: Merlot, Mustoasa, Feteasca, and Chasla
were first analyzed by HPLC (high performarce liquid chromatography)
regarding their flavonol content.
The aim of this research was to evaluate the efficiency
of ORAC, DPPH and ABTS radicals and to estimate the antioxidative
capacity of grape seed extracts. The antioxidative
activity of the extracts was determined through:
•
•
•
Oxygen radical absorbance capacity assay (ORAC)
2,2’-diphenyl-1-pichrylhydrazyl assay (DPPH)
Trolox equivalent antioxidant capacity assay (TEAC)
Total phenolic compounds content was determinated
colorimetrically using Folin-Ciocalteu reagent.
Material and Methods
P r e p a r a t i o n o f G r a p e S e e d
e x t r a c t s
Seeds of the Vitis vinifera grape were obtain from
Recas area (Bihor, RO). Grape seed were first grinded until
a powder was obtained, which was afterwards deoiled with
hexan (1 part of powder to 10 parts of hexane w/v). The solid
residue was kept under the hood in the dark to evaporate the
hexane. Seed extracts were prepared for analysis by mixing
the powder with metanol/water/acetic acid (70 : 29.05 : 0.5,
v/v/v) for a ratio of 1 part powder to 10 parts solvent (w/v).
The mixture was sonicated for 15 min and shaken for 30 min
at 4,000 rpm. The extract was concentrated in vacuum rotary
evaporator at 40 °C. Volume of the concentrate was then
s622
adjusted to obtain a concentration of 1 g solids ml –1 by adding
a predetermined volume of methanol 7 .
O R A C A s s a y
ORAC assay measures antioxidant inhibition of peroxyl
radical induced oxidation, reflecting classical radical chain
breakage of antioxidant activity, by hydrogen atom transfer.
The ORAC assay was performed as described by Ou et. al. 4 .
D P P H A s s a y
DPPH assay is based on the measurement of the reduction
ability of antioxidants toward DPPH •+ . The kinetics
of 400 µl grape seed extract in 2.8 ml of DPPH (80 µM
in etanol) were registered in 30 min by monitoring DPPH
disappearance at 515 nm.
T E A C A s s a y
TEAC assay asseses the capacity of a compound to scavenge
ABTS radical (ABTS •+ ). Intensely colored radical cation
ABTS •+ is formed by peroxyl radical oxidation of ABTS.
The antioxidant ability is measured as the ability of test compounds
to decrease the color formation. Using the method
of Arnao et. al. (2002) 1 the interaction between the antioxidants
and the ABTS ·+ was monitored spectrophotometricaly
at 734 nm.
F o l i n - C i o c a l t e u A s s a y
In Folin-Ciocalteu assay 250 µl extract were mixed with
1.25 ml of Folin-Ciocalteu reagent and 1.9 ml of sodium
carbonate respectively and allowed to react for 2 hours.
The absorption was measured with a Biotek Synergy HT
spectrophotometer. The total phenolic compounds content
was expressed as gallic acid equivalents (GAE mg g –1 dry
weight DW).
Results and Discussion
The four grape seed extracts were analyzed by HPLC-
UV, Merlot variety having 80 % of flavanols content, Feteasca
50 %, Mustoasa 40 %, and the poorest flavanol content was
for Chasla, only 20 % (data not shown). Table I and Fig. 1.
shows the value obtained for the antioxidant capacity assays.
ORAC, TEAC and DPPH values are expressed in µM Trolox
g –1 DW. The antioxidant activity using TEAC and ORAC
ranged from 86 to 280, and respectively from 100–183 µM
Trolox g –1 DW. From the four grape seed extracts, Merlot and
Table I
Antioxidant activity of grape seed extracts as determined by ORAC, DPPH, TEAC and Folin-Ciocalteu assay
Sample name µM Trolox g–1 DW mg GAE 100 mg –1 DW
ORAC DPPH TEAC Folin-Ciocalteu
Merlot 183.73 ± 2.4 1,140 ± 0.08 280.3 ± 1.8 651.2 ± 0.02
Mustoasa 123.1 ± 0.2 424 ± 0.09 129.6 ± 0.6 467.5 ± 0.04
Feteasca 155.3 ± 2.1 656.1 ± 1.3 202.1 ± 0.6 645.2 ± 0.01
Chasla 100.7 ± 1.8 67.2 ± 1.1 86.18 ± 3.1 423.2 ± 0.01