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Antioxidant characteristics of leaves, twigs, and acorns from two Serbian oak species Quercus robur L. and Quercus petraea L. from Vojvodina province (northern Serbia) were investigated. 80% ethanol (in water) extracts were used for antiradical power (ARP) determinations against DPPH(•), (•)NO, and O2 (•-) radicals, ferric reducing antioxidant power (FRAP), total phenol, tannin, flavonoid, and proanthocyanidin contents. Permanganate reducing antioxidant capacity (PRAC) was determined using water extracts. Beside, mentioned parameters, soluble proteins, lipid peroxidation (LP), pigments and proline contents were also determined. The data of different procedures were compared and analyzed by multivariate techniques (correlation matrix calculation and principal component analysis (PCA)). PCA found that investigated organs of two different oak tree species possess similar antioxidant characteristics. The superior antioxidant characteristics showed oak leaves over twigs and acorns and seem to be promising source of antioxidants with possible use in industry and pharmacy.
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e Scientic World Journal
Volume , Article ID , pages.//
Research Article
Antioxidant Characterization of Oak Extracts Combining
Spectrophotometric Assays and Chemometrics
Boris M. PopoviT,1Dubravka Štajner,1RuDica Cdero,1Saša OrloviT,2and Zoran GaliT2
ca 8, 21000 Novi Sad, Serbia
2InstituteofLowlandForestryandEnvironment,UniversityofNoviSad,Antona ˇ
Cehova 13, 21000 Novi Sad, Serbia
Correspondence should be addressed to Boris M. Popovi´
Received  August ; Accepted  September 
Academic Editors: N. Ercal and Z. Gao
Copyright ©  Boris M. Popovi´
c et al. is is an open access article distributed under the Creative Commons Attribution
License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly
Antioxidant characteristics of leaves, twigs, and acorns from two Serbian oak species Quercus robur L. and Quercus petraea L. from
Vojvodina province (northern Serbia) were investigated. % ethanol (in water) extracts were used for antiradical power (ARP)
determinations against DPPH,NO, and O2∙− radicals, ferric reducing antioxidant power (FRAP), total phenol, tannin, avonoid,
and proanthocyanidin contents. Permanganate reducing antioxidant capacity (PRAC) was determined using water extracts. Beside,
mentioned parameters, soluble proteins, lipid peroxidation (LP), pigments and proline contents were also determined. e data
of dierent procedures were compared and analyzed by multivariate techniques (correlation matrix calculation and principal
component analysis (PCA)). PCA found that investigated organs of two dierent oak tree species possess similar antioxidant
characteristics. e superior antioxidant characteristics showed oak leaves over twigs and acorns and seem to be promising source
of antioxidants with possible use in industry and pharmacy.
1. Introduction
Quercus trees, commonly known as oaks, belong to the
family Fagaceae. ey comprise  species worldwide [].
European oak corresponds well with these requirements and
is mainly represented by Quercus robur L. (pedunculate) and
Quercus petraea (Matt.) Liebl. (sessile oak). Oak wood is
valued for its mechanical properties and durability. It has
been widely used since prehistoric times []. Pedunculate is
the dominant tree species of natural forests in the area of
at Srem and also in whole region of Vojvodina, northern
Serbia. Besides pedunculate, sessile oak is the most valuable
oak in Serbia []. In the forestry fund of Serbia, there is
the signicant participation of sessile oak (.%) []. Oaks
are the major source of hardwood lumber and also they are
used for ornaments. e wood is durable and tough and also
attractively grained. It is especially valued in shipbuilding and
construction and for ooring, furniture, barrels, and veneer.
e bark of some oaks has been used in medicine, in tanning,
as a symbol of power []. In Serbia, oak is a sacred tree, used
in Serbian Christmas traditions.
Acorns, the fruit of oak trees, have long been employed as
a source of hog feed, tannin, oil, and especially food because
of the high content of carbohydrates, amino acids, proteins,
lipids, and various sterols [,]. Quercus acorns were mainly
used for making bread or as a substitute for coee. Oak
kernels were traditionally used in medicine, particularly
e acorns of Q. robur contain various biologically active
compounds with antioxidant activity (tannins, gallic and
ellagic acid, and dierent galloyl and hexahydroxydiphenoyl
derivatives) [,]. It was also known that the bark of dierent
Quercus speciescontainspolyphenolicconstituents.us,the
bark of Q. petraea contains both hydrolysable and condensed
tannins, avanols, and oligomeric proanthocyanidins [].
From the bark of Quercus robur more than  compounds
(catechins and oligomeric and polymeric proanthocyanidins)
have been isolated [].
e Scientic World Journal
Polyphenols are secondary metabolites of plants that are
generally involved in defense against ultraviolet radiation
and pathogens. In food, polyphenols contribute to the color,
avor, odor, bitterness, astringency, and oxidative stability.
Recent biomedical investigations connected to the polyphe-
nols and antioxidant activity of a number of herbals and
proanthocyanidins oer protection against development of
cancers, cardiovascular diseases, diabetes, osteoporosis and
neurodegenerative diseases [,].
Kim et al. []investigatedphenolicproleinleavesof
ve dierent Quercus species and approved presence of many
chemical constituents. is study demonstrated dierences
in phenolic compounds content in dierent parts of plants.
Quercus salicina Blume, for example, possesses high levels of
gentisic and chlorogenic acids as well as avonoids naringin
and rutin in the leaf. Brossa et al. []establishedthatmajor
constituents in holm oak (Quercus ilex L.) leaves are avanols
and avonols. According to Kamalak et al. [], oak leaves
from some Quercus species (Q. branti and Q. libari)may
have a high potential nutritive value for small ruminant
animals in terms of rumen and whole tract digestion. It is
established that content of phenolic compounds in Quercus
species highly depends on the stage of maturity and expresses
seasonal variation [,].
Sanchez-Burgos et al. [] established that aqueous extracts
from leaves from dierent white Quercus species (Quercus
resinosa, Quercus laeta, Quercus grisea, and Quercus obtusata)
displayed high radical scavenging activity against DPPH
and OH radicals as well as antimicrobial activities and
antitopoisomerase activity only Q. resinosa leaves infusions.
sek et al. [] also pointed out that Q. robur cortex is
a promising plant material as the source of antioxidative and
antimicrobial activity.
Bearing in mind that antioxidant potential of two major
Serbian oaks Quercus robur L. and Quercus petraea L.has
not been studied well enough, especially their leaves and
twigs, the aim of this work was to investigate the in vitro
antioxidant and scavenging activities and also total phenol
(TPC), tannin (TAC), avonoid (FLC), Proanthocyanidin
(PAC), and proline contents as well as lipid peroxidation (LP)
in leaves, twigs, and acorns of these two Serbian oak tree
2. Materials and Methods
2.1. Plant Material and Extraction Procedure. is paper
presents antioxidant characteristics of two Serbian oak
species Quercus robur L. and Quercus petraea L. from
Vojvodina province, in northern Serbia. During September
, twigs, leaves, and acorns were picked to make average
samples (from  trees per one replicate). ree independent
replicates were made for both species. All samples were dried
in open air in the dark.
Aer that, g of the dried sample was nely ground
into a ne powder in a mill and extracted with  mL of
water for  h at C, followed by ltration. Prepared extract
determination. For all ARP determinations and FRAP the
similar extraction tool was used, with % EtOH (in water) as
an extractant. For TPC and TAC acidic ethanol (. mol/dm3
HCl in EtOH) was used as an extractant. For determination
of DPPH,NO, and O2∙− ARP, % EtOH extracts were
evaporated to dryness and the dry residues were redissolved
again in % EtOH (in water) to obtain mass concentration
 mg/mL (for DPPH,NO and O2∙− ARP determination).
2.2. Lipid Peroxidation, Proline, Soluble Protein, and Pig-
ment Contents. Lipid peroxidation (LP) was estimated based
on thiobarbituric acid (TBA) reactivity. Samples were
evaluated for malondialdehyde (MDA) production using
a spectrophotometric assay. e extinction coecient of
, mol−1 cm−1 at  nm for the chromophore was used
to calculate the colour intensity of the MDA-TBA complex in
the supernatant [].
Proline accumulation was determined by the method
as described by Paquin and Lechasseur []. Proline was
determined aer extraction with sulphosalicylic acid, and
reaction with ninhydrin. A standard curve of proline was
used for calibration and was measured by its absorbance at
 nm.
Pigments were extracted with acetone and determined
spectrophotometrically using molar extinction coecients
according to von Wettstein []. Soluble protein content was
determined by the method of Bradford [].
2.3. Total Phenol, Tannin, Flavonoid, and Proanthocyani-
din Contents. Total polyphenols were determined by Folin-
Ciocalteu procedure []. e amount of total polyphenols
was calculated as a catechin equivalent from the calibration
curve of catechin standard solutions (covering the concentra-
tion range between . and . mg/mL) and expressed as mg
catechi/ g dr y plant material.
Total tannin content was determined by Folin-Ciocalteu
procedure as above, aer removal of tannins by their adsorp-
tion on insoluble matrix (polyvinylpolypyrrolidone, PVPP).
Calculated values were subtracted from total polyphenol
contents and total tannin contents expressed as mg cate-
chine/ g dry plant material.
Total avonoids were determined aer extraction of plant
material ( g) with extracting solvent methanol-water-acetic
acid ( :  : , V/V), according to Markham []. e
amount of avonoids was calculated as a rutin equivalent
from the calibration curve of rutin standard solutions and
expressed as mg rutin/ g of plant material.
Proanthocyanidins were determined by butanol-HCl
assay []. eir contents were expressed as mg leucoan-
thocyanidin/g of dry plant material, assuming that the
specic absorbance of leucoanthocyanidin was .
2.4. FRAP. Total antioxidant capacity was estimated accord-
ing to the ferric reducing antioxidant power (FRAP) assay
[]. FRAP reagent was prepared by mixing acetate buer
( mM pH .), TPTZ (,,-tripyridyl-s-triazine) reagent
( mM in  mM HCl), and FeCl3H2(mM)inratio
e Scientic World Journal
::. Sample (L) was mixed with  mL of working
FRAP reagent and absorbance ( nm) was measured at 
minutes aer vortexing. FRAP value was calculated using
FRAP value =sample (– min)
standard (– min) .()
 MFe
2+ wasusedasastandard;FRAPunit=M
Total antioxidant capacity was expressed in FRAP units.
2.5. Permanganate Reducing Antioxidant Capacity. e
antioxidant sample and the potassium permanganate in
sulfuric acid media, leading to sample discoloration until
no colour is observed []. Variable amounts of samples
(-mL), depending on the intensity of the antioxidant
activity, were introduced in a  mL quartz vat containing
an oxidative mixture of . mL potassium permanganate
. M; . mL sulfuric acid  M, and (-)mL distilled
water. at moment was considered the zero time. e
spectrophotometer signal was then registered at  nm
until constant value. Subsequent decrease of potassium
permanganate concentration was determined based on a
previously prepared calibration curve. A calibration curve
was determined by preparing a series of six solutions
with dierent concentrations of potassium permanganate
and registering the absorbance for each of them. In order
to quantitatively compare the antioxidant activities, we
proposed the following formula:
50 =(standard)
(plant sample)(standard)
(plant sample)⋅
where 50 is antioxidant activity expressed, reected in the
time until the sample induces a decrease of the oxidizing
agent [potassium permanganate] concentration up to one
half, compared against a standard [ascorbic acid] (mmol
equivalent standard/g plant), (plant sample)isthetimeuntilthe
sample induces a decrease of the permanganate concentra-
tion up to one half (min), (standard)is the time until the stan-
dard (ascorbic acid) induces a decrease of the permanganate
concentration up to one half (min), (standard)is standard
(ascorbic acid) concentration (mmol/mL) [. mmol/mL],
(plant)is weight (g) of the plant sample submitted to
extraction [ g], (plant sample)is volume of the plant extract
submitted to the analysis [. mL], (standard)is volume of
the standard submitted to the analysis [ mL], and (extract)is
volume (mL) of the obtained extract [ mL].
2.6. Radical Scavenging Determinations. DPPH-RSC assay
was based on measurement of the loss of DPPH (,-
diphenyl--picrylhydrazyl) color aer reaction with test com-
pounds []. e DPPHradical is one of the few stable
organic nitrogen radicals, which bears a deep purple color.
is assay is based on the measurement of the reducing ability
of antioxidants toward DPPH.eabilitycanbeevaluated
by measuring the decrease of its absorbance. e widely used
decoloration assay was rst reported by Brand-Williams et
al. [].Appropriatevolumeofeachextractwasmixedwith
 M DPPHin methanol making up nal volume of . mL.
e mixtures were shaken vigorously and were stored in dark
for  min at room temperature. e decrease of absorbance
of the reaction mixtures regarding the control was monitored
spectrophotometrically at  nm.
NO-RSC was evaluated by measuring the accumulation
of nitrite (formed by the reaction of NO with oxygen),
according to the Griess reaction []. NO was generated by
sodium nitroprusside in buered aqueous solution. Appro-
priate volume of each extract was mixed with fresh pre-
NaH2PO4-Na2HPO4buer, . M, pH .) and NaH2PO4-
Na2HPO4buer (. M, pH .) making nal volume of
. mL. ese mixtures were illuminated at  lx and C
for  min. Aer illumination, each reaction mixture ( mL)
was mixed with Griess reagent (mL, .% N-(-naphtyl)-
ethylenediamine dihydrochloride (NEDA) in distilled water
and % sulfanilamide in % H3PO4). Reduction of nitrite
by the extracts was determined spectrophotometrically at
 nm, by measuring the decrease of absorbance of the
reaction mixtures regarding the control (containing the same
chemicals, except for the sample).
O2∙−-RSC assay was based on the capacity of crude
extracts to inhibit the photochemical reduction of nitro blue
tetrazolium (NBT) in the riboavin-light-NBT system [].
Each  mL of reaction mixture contained sodium phosphate
buer ( mM, pH .), methionine ( mM), riboavin
( M), EDTA ( M), NBT ( M), and extract solution.
Reaction systems were illuminated at  lx and Cfor
 min. e increase in absorbance at  nm was monitored.
e scavenging capacity was expressed as reduction percent-
age of NBT absorbance induced by sample.
For each sample three replicates were carried out. RSC
was calculated by the following equation:
RSC =0−1
0100, ()
where 0is control and 1is a sample solution absorbance.
e concentration (in the nal reaction media in each
method) that causes a decrease in the initial absorbance
(control) by % is dened as IC50.eIC
50 values for all
RSC determinations were determined by polynomial tting
of the inhibition values (RSC) using soware ORIGIN ..
e antioxidant capacity of the extracts was expressed as
antiradical power (ARP) and it was dened as
ARP = 1
IC50 100. ()
2.7. Statistical and PCA Analysis. Statistical comparisons
between samples were performed with Duncan t-test for
independent observations. Dierences were considered sig-
nicant at  < 0.05. e antioxidant test results were inves-
tigated with multivariate analysis. e correlation matrix was
calculated, giving the correlation coecients between each
pair of variables, that is, the analytical parameters tested.
e Scientic World Journal
Each term of the matrix is a number ranging from to+:
the + or sign indicates a positive or negative interdepen-
dence between variables (direction), and the absolute value
indicates the strength of the interdependence. Correlations
between dierent parameters were considered signicant at
 > 0.95( < 0.05). Autoscaling transformation of data for
phenolic parameters (TPC, TAC, FLC, and PAC) was done
using STATISTICA . and presented by graphic (Figure ).
3. Results and Discussion
3.1. Soluble Proteins, Proline, Pigment and MDA Contents.
Solubleproteincontentrangedfrom.(Q. robur twigs)
to . mg/g (Q. robur leaves); Proline content ranged from
. (Q. petraea acorns) to . g/g (Q. robur twigs); Chla
contentrangedfrom.(Q. robur acorns) to . mg/g
(Q. petraea leaves); Chlb content ranged from . (Q. robur
acorns) to . mg/g (Q. petraea leaves); Carotenoid content
ranged from . (Q. robur acorns) to . mg/g (Q. robur
leaves); MDA content ranged from . (Q. petraea acorns)
to . nmol/mg protein (Q. robur twigs), (Tables and ).
Signicant positive correlations were found between Chla
and Chlb ( = 0.9957), and also between carotenoids and
both chlorophylls ( = 0.84). Positive correlation was found
between proline content and MDA content ( = 0.4459).
Lipids are susceptible to oxidation and lipid peroxidation
products, such as MDA quantity, are potential biomarkers for
oxidative stress status in vivo. Proteins are also the direct tar-
get for Reactive Oxygen Species (ROS) because of their high
concentrations. eir oxidation may result in deamination,
decarboxylation, peptide backbone cleavage, cross-linking,
and many other chemical modications leading eventually to
inactivationof enzyme activity and accumulation within cells
and extracellular environment []. Furthermore, antioxidant
capacity and the ratio between reduced forms to oxidized
oxidative stress []. According to our results, the highest
accumulation of MDA was observed in twigs of both Quercus
increased level of oxidative stress.
Carotenoids, along with phenolics, are responsible for
bright colours of plants and are also powerful antioxidants.
Carotenoids can protect membranes against damage by free
radicals and retard the ageing processes []. e highest
content of pigments, carotenoids, and chlorophylls was found
in the leaves of both, especially Q. petraea.Prolineisan
amino acid that acts as an antioxidant—it reduces free
radicals in plant cells [,]. Its production is a self-defense
mechanism. Plant’s proline levels are an indicator of both
the environment stress and the plant’s response. Proline does
not interfere with normal biochemical reactions but allows
the plants to survive under stress []. e accumulation of
proline in plant tissues is also a clear marker for environ-
mental stress, particularly in plants under drought conditions
responses []. Positive correlation between free proline
content and LP intensity conrms both antioxidant and
defense natures of this amino acid.
3.2. Total Phenol, Tannin, Flavonoid, and Proanthocyani-
din Contents. Total phenol content ranged from . (Q.
petraea twigs) to .mg catechin/g (Q. petraea leaves);
Tannin content ranged from . (Q. petraea twigs) to
. mg catechin/g (Q. petraea leaves); Flavonoid content
ranged from . (Q. petraea twigs) to . mg rutin/ g
(Q. petraea leaves); Proanthocyanidine content ranged
from . (Q. petraea twigs) to  mg rutin/ g (Q.
robur leaves) (Table ). Signicant positive correlations were
observed between all mentioned parameters. e highest
positive correlation was observed between TPC and TAC
( = 0.9955). All phenolic parameters were signicantly
positively correlated with carotenoid content. Total phenol,
tannin, and avonoid contents were also signicantly posi-
tively correlated with both chlorophylls (a and b). Phenolic
parameters were analyzed by a multivariate approach and
results are showed by line plot of multiple variables (Figure ).
All phenolic parameters are negatively but not signicantly
correlated with LP parameter.
Our results are in accordance with that obtained by
cetal.[] who indicated that oak acorns from Q.
robur are material rich in polyphenols and tannins. We have
found similar results for Q. petraea acorns. Kamalak et al. []
evaluated nutritive values of browse leaves from ve oak
species, namely, Quercus branti,Quercus coccifera,Quer-
cus cerris,Quercus libari,andQuercus infectoria based on
their chemical composition. It was established that tannin
accordance with our results for Q. robur and Q. petraea.
Q. petraea and Q. robur arealsorichsourceofavonoids
and proanthocyanidins which are found in all plant organs,
especially in leaves. Flavonoid content found in leaves of Q.
petraea and Q. robur is in range of that found in Quercus
salicina Blume []. According to Salminen et al. ()
hydrolysable tannins were the dominant phenolic group in
leaves of all ages of Q. robur which is in well agreement with
our results. However, hydrolysable tannins and avonoid
glycosides showed highly variable seasonal patterns. Young
avonoid glycosides than old leaves, and vice versa for proan-
thocyanidins []. Although in smaller quantities, twigs also
contained all classes of polyphenols (Ta b l e  ). e obtained
results have provided further grounds for establishing Q.
robur and Q. petraea leaves, acorns, and twigs as a source for
functional food preparation.
3.3. FRAP and PRAC Methods. FRAP values ranged from
. (Q. robur twigs) to . FRAP units (Q. petraea
leaves); PRAC values ranged from . (Q. petraea twigs)
to . mmol ascorbate eq./g (Q. petraea acorns) (Ta b l e  ).
FRAP was signicantly positively correlated with phenolic
parameters (TPC, TAC, and FLC) and with pigment (Chla,
Chlb, and Car) contents. e highest positive correlation was
observed between FRAP and TAC ( = 0.9587). PRAC value
was positively correlated with O2∙−-ARP ( = 0.6196)and
negatively correlated with LP (= −0.8113).
Benzie and Strain [] introduced FRAP as a simple
and automated test measuring the ferric reducing ability
e Scientic World Journal
T : Total phenol, tannin, avonoid, proantocyanidine, chlorophyll a and b, carotenoid, and proline contents in oak twigs, leaves, and
acorns of two Serbian oak species Quercus robur L. and Quercus petraea L.
Plant organ Locality TPC
(mg catechin/g)
(mg catechin/g)
(mg rutin/ g)
(mg leukocyani-
dine/ g)
Twigs Q. robur .a.a.a.a.a.a.a.a
Q. petraea .   b.b.a.b.a.b.b.b
Leaves Q. robur .c.c.bc.b.c.c.c
Q. petraea .d.d.c.d.c.d.d.d
Acorns Q. robur .e.e.a.e.d.e.e.ad
Q. petraea .e.e.d.a.a.a.ab .e
Values with the same letter, in each colon, are not signicantly dierent according to Duncan test (𝑃 < 0.05).
∗∗TPC: total phenolic content; TAC: tannin content; FLC: avonoid content; PAC: proanthocyanidin content; Chla and Chlb: chlorophyll a and b contents;
Car: carotenoid content; Pro: proline content.
T : Protein content, DPPH, NO, and O2∙−-antiradical powers, permanganate reducing antioxidant capacity, ferric reducing antioxidant
power, and lipid peroxidation in oak twigs, leaves, and acorns of two Serbian oak species Quercus robur L. and Quercus petraea L.
organ Locality Prot.
(nmol/mg prot.)
Twigs Q. robur .a.a.a.a.a.a.a
Q. petraea .b.b.b.b.a.a.b
Leaves Q. robur .c.    c.c.b.b.b.c
Q. petraea .d.d.d.c.c.c.c
Acorns Q. robur .e.d.e.d.d.d.d
Q. petraea .b.e.e.e.e.e.d
Values with the same letter, in each colon, are not signicantly dierent according to Duncan test (𝑃 < 0.05).
∗∗Prot.: proteins; ARP: antiradical power; ARP = ((/IC)); IC: the concentration of an sample at which % inhibition off ree radical activityis obs erved;
PRAC: permanganate reducing antioxidant capacity; A: antioxidant activity reected in time until the sample induces a decrease of the oxidizing agent
(potassium permanganate) up to one half, compared against a standard (ascorbic acid); A = mmol ascorbate eq./g; FRAP: ferric reducing antioxidant power;
FRAPunit=𝜇mol/dmFe+; LP: lipid peroxidation.
of plasma and a novel method for assessing “antioxidant
power.” Ferric to ferrous ion reduction at low pH causes a
colored ferrous-tripyridyltriazine complex to form. Accord-
ingtoMaqsoodandBenjakul[] tannic acid showed
higher FRAP value in comparison with other investigated
phenolics including catechin which is in agreement with
our observation that the highest positive correlation was
found between FRAP and TAC parameter. Same reaction
mechanism based on electron transfer explains high positive
correlations between FRAP and phenolic parameters (TPC,
TAC, and FLC ) [ ]. According to FRAP method, antioxidant
capacity of oak samples, especially leaves, was relatively
high comparing with other plants []. FRAP value
was more or less positively correlated with all investigated
parameters excluding LP, where negative correlation was
found (.).
PRAC method was rstly introduced by Cacig and Szabo
[] as a simple spectrophotometric method for evaluation
of antioxidant capacity and later compared with other total
antioxidant capacity methods []. Unlike the oak leaves
where the highest FRAP was found, oak acorns showed the
highest PRAC. High positive correlations with O2∙−-AR P
indicate that the same structures are probably responsible for
superoxide scavenging and for reduction of permanganate
in acidic media. e highest negative correlations of both
parameters with LP also indicate that scavengers of super-
oxide and substances with high reducing potential against
permanganate are mostly responsible for suppression of LP.
3.4. Antiradical Power Determinations. DPPH-ARP ranged
from . (Q. petraea twigs) to . (Q. robur acorns); NO-
ARP ranged from . (Q. robur acorns) to . (Q. robur
leaves); O2∙−-ARP ranged f rom . (Q. robur twigs) to .
(Q. robur acorns) (Tab l e  ). DPPH-ARP and NO-ARP were
positively correlated with all phenolic parameters (TPC, TAC,
FLC, and PAC), pigments (Chla, Chlb, and Car), and FRAP.
In contrast to them, O2∙−-ARP showed rather less positive
correlations with phenolic parameters, pigments, and FRAP
but relatively high positive correlation with PRAC (.).
Among investigated ARP parameters, only O2∙−-ARP sh owed
signicant negative correlation with LP (= −0.8360).
All three ARP power determinations against DPPH,
O2∙−, and NO radicals generally proceed also via hydrogen
atom transfer or electron transfer mechanism depending on
present antioxidant structure, pH, dielectric constant of the
solvent, and so forth []. DPPH and O2∙−-ARP were corre-
lated with each other ( = 0.6776), while correlations with
NO-ARP were much lower. Signicant positive correlation of
e Scientic World Journal
−1.0 −0.5 0.0 0.5 1.0
Factor 1: 58.33%
Factor 2: 21.51%
F : Graph of loading plot of antioxidant markers for Serbian
oak species Quercus robur L. and Quercus petraea L. Prot.: proteins;
ARP: antiradical power; PRAC: permanganate reducing antioxidant
capacity; FRAP: ferric reducing antioxidant power; LP: lipid per-
oxidation; TPC: total phenolic content; TAC: tannin content; FLC:
avonoid content; PAC: Proanthocyanidin content. Chla and Chlb:
chlorophyll a and b contents; car: Carotenoid content; Pro: proline
content. Parameters with close interdependence and correlation are
close to each other and vice versa.
NO-ARP and carotenoids ( = 0.8525) indicated signicance
of carotenoid antioxidants for NO scavenging. Sindhu et al.
[] also established that carotenoids lutein and zeaxanthin
showed stronger antiradical potential against NO than DPPH
and O2∙− radicals. e highest DPPH- and O2∙−-ARP showed
acorns and the highest NO-ARP showed leaves Q. robur.
Rivas-Arreola et al. []alsoinvestigatedantioxidantactivity
of oak (Q. sideroxyla,Q. Eduardii,andQ. resinosa)leaves
infusions against free radicals and obtained similar results
for radical scavenger capacities. Oak twigs expressed lower
DPPH, O2∙−,andNOARPincomparisonwithleavesand
acorns but also relatively high antiradical potential.
3.5. PCA Analysis. e original data set was renormalized by
an autoscaling transformation (data not shown) and dierent
parameters were analyzed by a multivariate approach. e
loadings plot is presented by Figure  and the scores plot by
Figure . e scree plot (data not shown) indicates that the
rst two principal components account for .% of the total
variance (PC = . and PC = .).
As reported in the loadings plot (Figure ), antiradical
power parameters (DPPH,NO, and O2∙−-ARP), FRAP,
polyphenol (TPC, TAC, FLC, and PAC), protein, and pigment
contents are positioned closely due to the signicant positive
correlations among them. PRAC and O2∙− ARP are partially
isolated and located opposite to LP as a parameter of oxi-
dative stress. Positive correlations were also found among
−6 −5 −4 −3 −2 −1 01234
Factor 2: 21.51%
Factor 1: 58.33%
Twigs QR
Twigs QPLeaves QR
Leaves QP
Acorns QR
Acorns QP
robur L. (QR) and Quercus petraea L. (QP). Quercus robur L. (QR)
and Quercus samples that are close to each other possess similar
antioxidant statuses.
DPPH-ARP and proteins and also between NO-ARP and
proline content.
PCA found three dierent clusters of oak samples based
on antioxidant characteristics: leaves, acorns, and twigs from
investigated species are grouped (Figure ). Leaves dier
from twigs and acorns predominantly by Factor  (where
the major contributors are polyphenols and FRAP). And the
dierence between twigs and acorns is based on Factor 
(where the major contributors are LP, PRAC, and O2∙−-ARP).
Opposite direction of LP on one side and PRAC O2∙−-ARP
on another side indicates that the major contributors against
lipid peroxidation are components which are antioxidants
which can easily reduce permanganate and also scavenge
O2∙−-radicals. Very close interdependence was observed
between leaves and twigs from both species, but twigs from
two Quercus species showed slightly higher dierences. Line
plot of multiple variables aer autoscaling transformation
of polyphenolic content parameters (TPC, TAC, FLC, and
PAC ) w a s s h o w n i n Figure . It is obvious that polyphenolic
parameters for leaves are separated and are greater than the
same parameters for acorns and twigs.
4. Conclusion
is investigation pointed out antioxidant potential of both
Serbian oak species (Q. robur and Q. petraea). Leaves from
both oak species possessed high contents of total phenols,
tannins, avonoids, proanthocyanidins, and pigment con-
tents. Antiradical power parameters were also very high for
oak leaves and LP intensity was relatively low. Ferric reducing
antioxidant capacity was the highest in oak leaf extracts,
especially for Q. petraea. Among investigated leaf extracts
which are signicant source of phenolic compounds, oak
acorns showed also high antioxidant potential and the lowest
LP intensity. Antioxidant capacity values including DPPH,
NO and O2∙−-ARP, and FRAP showed high positive correla-
tions among themselves and also with polyphenol parameters
e Scientic World Journal
Twigs QR
Twigs QP
Leaves QR
Leaves QP
Acorns QR
Acorns QP
Line plot of multiple variables
F : Line plot of multiple variables aer autoscaling transfor-
mation of phenolic content parameters (TPC, TAC, FLC, and PAC).
Quercus robur L. (QR) and Quercus petraea L. (QP). TPC: Total
phenolic content; TAC: Tannin content; FLC: Flavonoid content;
PAC: Proanthocyanidin content.
(TPC, TAC, FLC, and PAC), protein, and pigment contents.
Permanganate PRAC and O2∙−-ARP were selected as the
best antioxidant markers for oak trees because of the highest
negative correlations with LP intensity. Considering high
antioxidant potential of investigated organs of Serbian oak
species (Q. robur and Q. petraea), besides acorns, oak leaves,
and even twigs, could be recommended as source of natural
antioxidants and promising source of pharmaceuticals with
possible use in industry and pharmacy.
PCA: Principal component analysis
RSC: Radical scavenging capacity
ARP: Antiradical power
PRAC: Permanganate reducing antioxidant
FRAP: Ferric reducing antioxidant power
LP: Lipid peroxidation
TPC: Total phenolic content
TAC: Tannin content
FLC: Flavonoid content
PAC: Proanthocyanidin content
Chla and Chlb: Chlorophyll a and b contents
Car: Carotenoid content
Pro: Proline content.
is research is part of Project no. III which is nan-
cially supported by the Ministry of Science, Technologies and
Development of the Republic of Serbia.
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... Literature is replete with information about the biological activities of extracts and secondary metabolites isolated from acorns, stem barks, oak molasses and leaves of Q. robur L. These biological activities include anti-inflammatory, antimicrobial, hepatoprotective, gastro-protective, anti-oxidative and astringent activity (Andrenšek et al., 2004;Moharram et al., 2015;Popović et al., 2013;Zdravkovic et al., 2015). ...
... All analysis were performed under R v 3.6.1. (Popović et al., 2013). These differences in value could be ascribed to changes in botanical and geographical origin. ...
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The leaves and stem bark extracts of Quercus robur L. grown in South Africa have been investigated for their bioactive metabolites using UHPLC-QToF-MS. The UHPLC-QToF-MS profiling of the various extracts revealed the presence of twenty-seven compounds. These compounds were majorly grouped into flavonoids, phenolic acid and triterpenoids such as alnusiin, (+)-catechin, cis-3,4-leucopelargonidin, (-)-gallocatechin, ellagic acids, gallic acid, luteoforol, kaempferol-3-o-(6-o-cis-coumaryl)glucoside, myricitrin, neohesperidin, neriifolin, pheophorbide a pheophytin a, procyanidin B5, pedunculagin, quercetin 3-O-[beta-D-xylosyl-(1- > 2)-beta-D-glucoside and quercitrin.. The aqueous bark extract had the highest total phenol content (TPC) (320 mg GAE/g DW) and total flavonoids content (TFC) (505 mg QE/g DW), whereas the 80% aqueous acetone leaves extract had the highest proanthocyanidins levels (Pro) (433 CE/g DW). The 80% aqueous acetone extract had the best 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) scavenging capability with an IC50 value of 8.16 µg/mL. The 80% aqueous ethanol extract had the highest 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) scavenging ability with an IC50 value of 7.73 µg/mL. The aqueous leaves extract had the best ferric reducing antioxidant power assay (FRAP) ability with values of 558 µg/mL GAE. The most significant inhibitory effects on digestive enzyme activity were obtained with the 80% aqueous methanol bark and aqueous bark extracts at the concentration of 7.81 µg/mL, yielding inhibition values of 62 and 97% on α-amylase and α-glucosidase, respectively higher than the positive control used (acarbose). These findings calls attention to the phytochemical content, antioxidant and inherent antidiabetic activity of Q. robur L. grown in South Africa and therefore potentiate its potential application in the food and pharmaceutical industries, with a focus in the prevention of diabetes.
... The Quercus genus is one of the most important genera of the Fagaceae family, as it comprises over 600 species, mainly trees, that are widely spread in the Northern Hemisphere, mainly in Europe, Asia, and the Americas (especially North America) [1,2]. Due to the properties of their wood, oaks have great economic importance, and they are used in different fields, such as construction, furniture, and barrel production [3,4]. Considering the current spread of the genus and the value of oak wood, the large amount of oak bark that results after wood processing is considered natural waste. ...
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The species of the Quercus genus, including Quercus cerris L., are widely used and their wood represents a valuable material utilized for various purposes. The intense industrial processing of wood results in a considerable amount of poorly-used natural by-products, such as bark, and a loss of potentially useful raw materials. Thus, the aim of our study was to evaluate the phytochemical characteristics and potential biological activities of Quercus cerris bark extracts obtained by optimizing the parameters of microwave assisted extraction (MAE). The optimum conditions for MAE were determined using a design of experiments (DoE) model, which set the experimental variables (irradiation time and microwave power) and their values. Aqueous and hydroalcoholic extractions were performed and the optimum parameters of extraction were determined for both solvents. The total polyphenolic and tannin contents were determined. The biological activities representative of antioxidant capacity were determined using two free radical scavenging methods, the DPPH and ABTS methods, and the antibacterial activity was assessed with the microdilution method. The results showed different optimal extraction conditions for aqueous (30 min at 850 W) and hydroalcoholic (18 min at 650 W) extracts. A higher yield of total polyphenols was observed in the hydroalcoholic bark extract (403.73 ± 7.35 mg gallic acid equivalents/g dried weight); however a lower level of tannins was registered in comparison to the aqueous extract. In addition, both extracts exerted high antioxidant activities, with the aqueous extracts having a stronger inhibitory effect against the DPPH radical. Moreover, the extracts exhibited antibacterial activity against the tested bacterial strains, especially against the Gram-positive strains and Klebsiella pneumoniae, with the hydroalcoholic extracts being more efficient overall. To conclude, the optimized MAE was an efficient method to extract phytochemical compounds with potential biological effects from Quercus cerris bark.
... These total quantities of flavonoids were lower than that obtained by Rtibi et al. (2017) for the aqueous extract of Q.I harvested from Fernena (Tunisia) which contained 18.54 mg g of extract. However, the Quercus robur L. and Quercus petraea acorns had lower amounts than those found in our study (26.17 mg /100g and 73.81mg / 100g) (Popovic et al., 2013). This difference could be attributed to the fact that the flavonoids vary considerably from genotype to genotype, and from fruit ripening (Tadmor et al., 2010). ...
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The crude fat (7.2%, 5.6%), crude protein (3.71%, 2.9%), dietary fiber (2.6%, 2.7%) and total ash (2.19%, 2.47%) contents were determined for Quercus Ilex (Q.I) and Quercus coccifera (Q.C), respectively. The main fatty acids in acorn oils of quercus were oleic (54.77%, 49.88%), linoleic (23.04%, 28.25%), and palmitic acid (18.23%, 17.57%) in Q.I and Q.C species, respectively. The sterol composition for acorn oil Q.C was determined for the first time in this work. The contents of essential amino acids, in acorns of Q.I and Q.C were determined and some of them were within the FAO reference values. Acorn seeds were also a good source of K, P, Ca and Mg. The ethanolic extracts of acorns Q.I and Q.C were rich in phenolic compounds. The starch extracted from the seeds of acorns had a ratio between the contents of amylose and amylopectin 31/69, 36/64 for Q.I and Q.C, respectively. The current results show the potential of these two studied species of acorn and their uses as food resources.
... According to Popović et al. 2013;Vinha et al. (2016) most wild edible nuts of Quercus species such as Q. acuta, Q. acutissima, Q. alba, Q. cerris, Q. faginea, Q. glauca, Q. ilex, Q. macrocarpa, Q. marilandica, Q. muhlenbergii, Q. myrsinaefolia, Q. palustris, Q. petraea, Q. phylliraeoides, Q. pyrenaica, Q. robur, Q. rubra, Q. rotundifolia, Q. salicina, Q. suber, and Q. virginiana are rich in polyphenolics, especially in phenolic acids (particularly gallic and ellagic acids and their derivative compounds), flavonoids (particularly flavan-3-ols), and tannins. Besides, López-Hidalgo et al. (2020) investigated some phytochemicals of Quercus ilex and reported the seed of the plant is a rich source of phenolic compounds (benzoics, cinnamics, coumarins, stilbenes, flavonoids, lignans, and tannins), which are important antioxidant molecules. ...
Since the world’s demand for inexpensive natural food and medicine is extensively increasing, thus, emphasis should be given to enhance the usage of underutilized forest-based products, such as seeds and nuts for health care and disease prevention. Forest-based edible seeds and nuts are those forest products that can be used as a staple or main dish, minor food supplements, thickening agents, condiments, and food flavors. They are a rich source of phytoconstituents, macronutrients, and micronutrients, such as protein, fatty acid, polyphenol, carbohydrate, fiber, vitamins, and minerals. These seeds and nuts are part of the cultural and genetic heritage of different regions of the world taken either directly or after processing. They are capable of reducing the risk of different ailments and help to reduce oxidative stress. Thus, they prevent the development of chronic diseases, including diabetes, cancer, cardiovascular disease, neurogenesis, and inflammation. This book chapter aims to discuss some edible forest-based seeds and nuts, their nutrient (micro and macromolecules), phytochemical composition, their biological activities, and their roles in health care and disease prevention.
... Hydro-ethanolic extract from red raspberry fruit was shown to inhibit UVB-induced secretion of matrix metalloproteinase 1 and 3 and inflammatory factors IL-6 and IL-1β, while promoting type I procollagen synthesis, thus exhibiting anti-photoaging effects [5]. Other types of hydrophilic and lipophilic extracts obtained from berries and from wood waste products (such as oak acorns) also exhibit antioxidant and anti-carcinogenic activity [6][7][8][9][10]. The above-mentioned extracts are rich in bioactives which are usually sensitive to heat, light and air, thus requiring effective carriers and mild processing conditions to preserve their activity. ...
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This study focuses on the development of biocompatible oil-in-water (O/W) nanoemulsions based on polyglycerol esters, as promising carriers for natural actives: red raspberry seed oil—RO and hydro-glycolic fruit extracts from red raspberry—RE and French oak—FE. Nanoemulsions were obtained via phase inversion composition (PIC) method at room temperature by dilution of microemulsion phase, confirmed by visual appearance, percentage of transmittance, microscopic, rheological and Differential Scanning Calorimetry (DSC) investigations. The results have shown that the basic RO-loaded formulation could be further enriched with hydro-glycolic fruit extracts from red raspberry or French oak, while keeping a semi-transparent appearance due to the fine droplet size (Z-ave: 50 to 70 nm, PDI value ≤ 0.1). The highest antioxidant activity (~92% inhibition of the DPPH radical) was achieved in the formulation containing both lipophilic (RO) and hydrophilic antioxidants (FE), due to their synergistic effect. The nanoemulsion carrier significantly increased the selective cytotoxic effect of RO towards malignant melanoma (Fem-X) cells, compared to normal human keratinocytes (HaCaT). In vivo study on human volunteers showed satisfactory safety profiles and significant improvement in skin hydration during 2 h after application for all nanoemulsions. Therefore, polyglycerol ester-based nanoemulsions can be promoted as effective carriers for red raspberry seed oil and/or hydro-glycolic fruit extracts in topical formulations intended for skin protection and hydration.
... Acorn, the fruit of Oak (Quercus tree) has been reported to contain vitamins, nutrients, carbohydrates, and minerals. It also contains considerable amounts of phenolic, tannin, catechin, epicatechin, and gallocatechin components [58,59]. Regarding the role of microbes and the oxidative inflammatory process in inducing colitis, the initial inferences could be drawn based on the beneficial effects of the antibacterial, antioxidant, and anti-inflammatory properties of QB [25,27,60]. ...
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Objectives: Ulcerative colitis is a common subtype of persistent inflammatory bowel disease with high morbidity consequences. Despite unknown definite pathogenesis, multiple anti-inflammatory medications are used for its treatment. Traditionally, Quercus brantii (QB), mostly available in the Middle East, has been used for gastrointestinal disorders. Other beneficial effects associated with QB include reduction of oxidative stress, inflammations, homeostatic instability, and improvement in clinical conditions. Materials and methods: This experimental study was designed to assess the possible therapeutic effects of QB on UC and compare its effects with those of sulfasalazine. Of the 70 Wistar rats clustered in seven groups, ten received only alcohols and sixty were confirmed to be suffering from trinitrobenzene sulfonic acid- (TNBS-) induced colitis. Four groups received different dosages of QB extract via oral and rectal routes, one received sulfasalazine, and the other remaining two groups received nothing. The effects of QB were evaluated by assessing macroscopic and histologic scoring, measuring inflammatory mediators, and determining oxidative stress markers. Results: Comparing to the untreated TNBS-induced control groups, QB-treated groups showed a dose- and route-dependent improvement comparable with sulfasalazine. Treating rats with QB reduced the microscopic and macroscopic damage, decreased TNF-α, IL-6, NO, MPO activity, and MDA content, increased superoxide dismutase (SOD) activity, and reduced body weight loss. Conclusions: Our data recommended the anti-inflammatory and antioxidant effects of QB extract in a dose-dependent manner.
... The white oaks (section Quercus), live oaks (series Virentes) golden cup or intermediate oaks (section Protobalanus) and red oaks (section Lobatae) are present in America. The cycle cup oaks (subgenus Cyclobalanopsis) are found in Asia and the white oaks along with black oaks (section Cerris) are extended into Eurasia [1][2][3]. ...
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The Quercus genus provides a large amount of biomaterial with many applications in fields like pharmaceutics, cosmetics, and foodstuff areas. Due to the worldwide dissemination of the genus, many species were used for centuries in traditional healing methods or in the wine maturing process. This review aims to bring together the results about phytoconstituents from oak extracts and their biological applicability as antioxidants, antimicrobial, anticancer, etc. The literature data used in this paper were collected via PubMed, Scopus, and Science Direct (2010–June 2020). The inclusion criteria were papers published in English, with information about phytoconstituents from Quercus species (leaves, bark and seeds/acorns) and biological activities such as antioxidant, antibacterial, antiobesity, anti-acne vulgaris, antifungal, anticancer, antiviral, antileishmanial, antidiabetic, anti-inflammatory. The exclusion criteria were the research of other parts of the Quercus species (e.g., galls, wood, and twigs); lack of information about phytochemistry and biological activities; non-existent Quercus species reported by the authors. The most studied Quercus species, in terms of identified biomolecules and biological activity, are Q. brantii, Q. infectoria and Q. robur. The Quercus species have been reported to contain several phytoconstituents. The main bioactive phytochemicals are phenolic compounds, volatile organic compounds, sterols, aliphatic alcohols and fatty acids. The, Quercus species are intensely studied due to their antioxidant, anti-inflammatory, antimicrobial, and anticancer activities, provided by their phytochemical composition. The general conclusion is that oak extracts can be exploited for their biological activity and can be used in research fields, such as pharmaceutical, nutraceutical and medical.
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Natural, semi-natural, and extensively managed oak woodlands and forests are prevalent across the world. These lands fulfil a range of ecosystem services, goods, and functions. Increasing natural and anthropogenic pressures impose threats to these lands. This paper first describes the Quercus genus and discusses management and mismanagement practices of oak systems. Then, the provisioning ecosystem services related with oak systems are reviewed, including: (1) oak’s agroforestry and silvopasture systems for the production of food, pasture, and additional products; (2) browsing of oak leaves and acorns by livestock; (3) harvesting of oak wood for timber; (4) cork oak stripping, and the uses of cork; (5) acorn-based foods and beverages; and (6) others uses, such as the production of medicines and extraction of tannins for the leather industry. We discuss the multi-purpose and multi-functional nature of oak systems, and demonstrate how they diversify sources of income for local communities, resulting in improved economic and food security. Further, we show the important role of woodlands certification, aimed at protecting oak systems while ensuring environmental equity. Also, we demonstrate how providing of financial support for reforestation and afforestation schemes of degraded oak woodlands, could restore ecosystem functioning and reverse land degradation. Then, we stress the need to involve traditional knowledge in restoration schemes of degraded oak systems. Lastly, we demonstrate how policymaking and legislation regarding the oak’s commercial plantations and farming systems could alleviate stresses imposed on the world’s oak woodlands and forests by producing alternative sources of wood for the timber industry.
Different approaches for the functional finishing of textile are now assessed as the popular subjects. In this respect wool fabrics were dyed with the leaves of oak and acorn (the different parts of the oak tree). The dyeing processes were carried out by using different mordants in different mordanting-dyeing processes. The samples were then investigated in terms of the obtained colors, fastness values, and UV protection features. It was observed that by use of acorn and oak leaves, the wool fabrics can be colored even when the mordanting agents were not used. In that case, the fastness values to washing, rubbing, and light were perfect too. Addition of the different mordanting agents caused different colors. Generally brown colors in different shades were obtained during the studies and the mordanting method was also found as responsible for the differences in obtained colors. Meanwhile, it was observed that the undyed wool has exhibited an UV protection feature but by using different natural dye sources, the UV protection feature of the fabrics was significantly increased. It was also found that UV protection properties of the fabrics increased with only mordants (without dyeing) as well.
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Gemmotherapy represents the most recent therapeutic technique that uses the properties of extracts from fresh meristematic plant tissues, mainly buds and sprouts, by macerating them in ethanol and glycerol. The harvesting time and the location can significantly affect the chemical composition of the buds. Therefore, this work aimed to point out the possible variability in the phenolic content and the antioxidant potential of extracts prepared from commonly grown trees in the Czech Republic. Extracts from buds collected during autumn and spring in three different localities were analysed using UHPLC-MS (ultra-high-pressure liquid chromatography) for the phenols profile. Five tests assays were used for the evaluation of the extract antioxidant potential. The sampling time positively affected the content of total phenols, flavonoids, and phenolic acids. The increased levels of total phenols and flavonoids in localities with high and medium pollution may be the result of the higher levels of NO and SO2, the main air pollutants. However, surprisingly, the content of phenolic acid showed the highest values in the area with the lowest pollution. The results of antioxidant tests did not completely correlate with the levels of phenolic metabolites, which may be due to the involvement of other active molecules (e.g., ascorbate, tocopherol, or proline) in the antioxidant machinery.
A protein determination method which involves the binding of Coomassie Brilliant Blue G-250 to protein is described. The binding of the dye to protein causes a shift in the absorption maximum of the dye from 465 to 595 nm, and it is the increase in absorption at 595 nm which is monitored. This assay is very reproducible and rapid with the dye binding process virtually complete in approximately 2 min with good color stability for 1 hr. There is little or no interference from cations such as sodium or potassium nor from carbohydrates such as sucrose. A small amount of color is developed in the presence of strongly alkaline buffering agents, but the assay may be run accurately by the use of proper buffer controls. The only components found to give excessive interfering color in the assay are relatively large amounts of detergents such as sodium dodecyl sulfate, Triton X-100, and commercial glassware detergents. Interference by small amounts of detergent may be eliminated by the use of proper controls.
In the present study we investigated the antioxidative properties of flowers and aboveground part of Anacamptis pyrimidalis L. from Vojvodina. Activities of antioxidant enzymes (superoxide dismutase, catalase, peroxidase, and glutathione peroxidase), quantities of malonyldialdehyde, superoxide and hydroxyl radicals and reduced glutathione and also the contents of chlorophylls a and b, carotenoids and soluble proteins were determined. Lipofuscin 'plant age pigments', total antioxidant capacity and scavenging activity were also determined. Our results indicated that the aboveground part of the plant exhibited higher antioxidant activity due to low MDA and lipofuscin pigment accumulation (2.82 nmol/mg protein; 92.90%), higher scavenging activity (54.16%) and antioxidant capacity (432.00 micromol Fe(2+)/dm(3)).
The nutritive values of browse leaves from five oak species, namely Quercus branti, Quercus coccifera, Quercus cercis, Quercus libari and Quercus infectaria were evaluated based on their chemical composition and gas production. Organic matter (OM) contents ranged from 929.8 to 952.1 g/kg DM; CP from 36.2 to 83.5 g/kg DM with Q. coccifera showing the lowest protein content. Crude fibre (CF) contents ranged from 305.9 to 509.2 g/kg DM. Gas production levels after 12 h for Q. branti and Q. libari were higher (P<0.001) than for other oak species. The rank order in terms of gas production performance was as follows: Q.libari=Q.branti>Q.infecteria>Q.coccifera>Q.cercis. Strong correlation was observed between gas production and crude fibre content of oak leaves. Crude fibre and tannin contents of oak leaves negatively correlated with gas production.Oak leaves from Q. branti and Q. libari may have a high potential nutritive value for small ruminant animals in terms of rumen and whole tract digestion. The variation in gas production reported in this study could result in differential intakes of oak leaves when given as sole diets, because gas production is negatively correlated with the level of crude fibre of oak leaves.