ArticlePDF Available

Hazel (Corylus avellana L.) leaves as source of antimicrobial and antioxidative compounds


Abstract and Figures

Aqueous extracts of leaves of different hazel (Corylus avellana L.) cultivars (Cv. M. Bollwiller, Fertille de Coutard and Daviana), were analysed by reversed-phase HPLC/DAD for the definition of their phenolic composition. Antioxidant potential was assessed by the reducing power assay, and the scavenging effect on DPPH (2,2-diphenyl-1-picrylhydrazyl) radicals and β-carotene linoleate model system. Their antimicrobial capacity was also tested against Gram positive (Bacillus cereus, Bacillus subtilis, Staphylococcus aureus) and Gram negative bacteria (Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae) and fungi (Candida albicans, Cryptococcus neoformans). Eight phenolic compounds were identified: 3-, 4- and 5-caffeoylquinic acids, caffeoyltartaric acid, p-coumaroyltartaric acid, myricetin-rhamnoside, quercetin 3-rhamnoside and kaempferol 3-rhamnoside. A p-coumaric acid, three myricetin and one quercetin derivatives were also detected. The hazel leaves extract presented high antioxidant activity in a concentration-dependent way, in general with similar behaviour of all cultivars. Gram positive bacteria revealed to be very sensitive to hazel leaf extract (MIC 0.1 mg/ml for B. cereus and S. aureus and 1 mg/ml for B. subtilis). However, Gram negative and the fungi displayed much lower sensitivity, being P. aeruginosa and C. albicans resistant at 100 mg/ml. Cv. M. Bollwiller exhibited the most potent antimicrobial activity.
Content may be subject to copyright.
Hazel (Corylus avellana L.) leaves as source of antimicrobial
and antioxidative compounds
Ivo Oliveira
, Anabela Sousa
, Patrı
´cia Valenta
, Paula B. Andrade
Isabel C.F.R. Ferreira
, Federico Ferreres
, Albino Bento
, Rosa Seabra
´cia Estevinho
, Jose
´Alberto Pereira
CIMO/Escola Superior Agra
´ria, Instituto Polite
´cnico de Bragancßa, Campus Sta Apolo
´nia, Apartado 1 172, 5301-855 Bragancßa, Portugal
REQUIMTE/Servicßo de Farmacognosia, Faculdade de Farma
´cia da Universidade do Porto, Rua Anı
´bal Cunha, 164, 4099-030 Porto, Portugal
Research Group on Quality, Safety and Bioactivity of Plant Foods, Department of Food Science and Technology, CEBAS (CSIC), P.O. Box 164,
30100 Campus Univ. Espinardo, Murcia, Spain
Received 14 November 2006; received in revised form 21 February 2007; accepted 29 April 2007
Aqueous extracts of leaves of different hazel (Corylus avellana L.) cultivars (Cv. M. Bollwiller, Fertille de Coutard and Daviana), were
analysed by reversed-phase HPLC/DAD for the definition of their phenolic composition. Antioxidant potential was assessed by the
reducing power assay, and the scavenging effect on DPPH (2,2-diphenyl-1-picrylhydrazyl) radicals and b-carotene linoleate model sys-
tem. Their antimicrobial capacity was also tested against Gram positive (Bacillus cereus,Bacillus subtilis,Staphylococcus aureus) and
Gram negative bacteria (Pseudomonas aeruginosa,Escherichia coli,Klebsiella pneumoniae) and fungi (Candida albicans,Cryptococcus neo-
formans). Eight phenolic compounds were identified: 3-, 4- and 5-caffeoylquinic acids, caffeoyltartaric acid, p-coumaroyltartaric acid,
myricetin-rhamnoside, quercetin 3-rhamnoside and kaempferol 3-rhamnoside. A p-coumaric acid, three myricetin and one quercetin
derivatives were also detected. The hazel leaves extract presented high antioxidant activity in a concentration-dependent way, in general
with similar behaviour of all cultivars. Gram positive bacteria revealed to be very sensitive to hazel leaf extract (MIC 0.1 mg/ml for
B. cereus and S. aureus and 1 mg/ml for B. subtilis). However, Gram negative and the fungi displayed much lower sensitivity, being
P. aeruginosa and C. albicans resistant at 100 mg/ml. Cv. M. Bollwiller exhibited the most potent antimicrobial activity.
Ó2007 Elsevier Ltd. All rights reserved.
Keywords: Hazel leaves; Phenolics; Antioxidant potential; Antimicrobial activity
1. Introduction
Although a number of Corylus species are found
throughout the world, C. avellana and its hybrids, are the
most important as regards nut production. Hazel is a tree
or bush which may grow to 6 m high, exhibiting deciduous
leaves that are rounded, 6–12 cm long and across, softly
hairy on both surfaces, and with a double-serrate margin.
It grows wild in Europe, and western Asia (Vaughan &
Geissler, 1997). Despite its wide cultivation for nuts collec-
tion, hazel leaves are also largely consumed as an infusion.
They are used in folk medicine for the treatment of haem-
orrhoids, varicose veins, phlebitis and lower members’
oedema, as consequence of its astringency, vasoprotective
and anti-oedema properties (Valnet, 1992).
Nowadays there is considerable evidence that the anti-
oxidants contained in fruits, vegetables and beverages play
an important role in the maintenance of health and in the
prevention of disease. In fact, plant-derived products con-
tain a wide range of phytochemicals, namely phenolic com-
pounds, with antioxidant capacity, providing protection
against the harmful effects resultant of oxidative stress
(Pereira et al., 2006; Proestos, Chorianopoulos, Nychas,
0308-8146/$ - see front matter Ó2007 Elsevier Ltd. All rights reserved.
Corresponding author. Tel.: +351 273 303277; fax: +351 273 325405.
E-mail address: (J.A. Pereira).
Food Chemistry 105 (2007) 1018–1025
& Komaitis, 2005; Seabra et al., 2006). Furthermore, there
is growing interest in using natural antimicrobial com-
pounds because of consumer pressure on the food industry
to avoid chemical preservatives and the increasing resis-
tance to antibiotics. With this regard the antimicrobial
capacity of phenolic compounds has also been reported
(Pereira et al., 2006; Proestos et al., 2005; Puupponen-
¨et al., 2001; Rauha et al., 2000; Zhu, Zhang, & Lo,
Previous studies on hazel leaves concerned the measure-
ment of the bidirectional reflectance distribution function
(Bousquet, Lache
´rade, Jacquemoud, & Moya, 2005) and
the determination of organochlorine pesticides (Barriada-
Pereira et al., 2004) hormone contents (Andre
´s, Ferna
´guez, & Rodrı
´guez, 2002), nitrate accumulation
(Stams & Lutke Schipholt, 1990), polycyclic aromatic
hydrocarbons (Howsam, Jones, & Ineson, 2000; Howsam,
Jones, & Ineson, 2001) and free polyamines (Rey, Dı
Sala, & Rodrı
´guez, 1998). In addition, the phenolic compo-
sition has already been described by our (Amaral et al.,
2005) and another research group (Fraisse, Carnat, Carnat,
& Lamaison, 1999) but, as far as we know, nothing has
been reported about their antioxidant and antimicrobial
The aim of this work was to determine the phenolics com-
position of the leaves of three hazel cultivars (Cv. M. Bollw-
iller, Fertille de Coutard and Daviana) grown in Portugal,
and to assess their antimicrobial and antioxidant abilities.
The phenolic compounds were identified and quantified by
HPLC/DAD. The antimicrobial activity was evaluated
against different microorganisms, namely Gram positive
(Bacillus cereus,Bacillus subtilis and Staphylococcus aureus)
and Gram negative (Pseudomonas aeruginosa,Escherichia
coli and Klebsiella pneumoniae) bacteria and fungi (Candida
albicans and Cryptococcus neoformans). The antioxidant
potential was tested in three distinct assays: reducing power,
scavenging of DPPH radicals and b-carotene bleaching.
2. Materials and methods
2.1. Samples
Hazel leaves were obtained from three Corylus avellana
L. cultivars: M. Bollwiller, Fertille de Coutard and Davi-
ana, and were collected on 3rd July 2006 in Bragancßa,
northeast of Portugal (6°460W, 41°490N, 670 m a.s.l.).
The orchard has a planting density of 3.5 7 m. The trees
were ten years old, and had been pruned when necessary.
No phytosanitary treatments were applied. The leaves were
collected from the middle third of branches exposed to sun-
light, put in plastic bags and immediately frozen at 20 °C.
The plant material was then freeze dried.
2.2. Extract preparation
For each cultivar, three powdered sub samples (5g;20
mesh) were extracted with 250 ml of boiling water for
45 min and filtered through Whatman no. 4 paper. The
aqueous extract was frozen, lyophilized and redissolved
in water at concentrations of 100 mg/ml and 10 mg/ml
for antimicrobial and antioxidant activities assays,
2.3. Phenolic compounds analysis
2.3.1. Standards and reagents
The standards used were from Sigma (St. Louis, MO,
USA) or Extrasynthe
`se (Genay, France). Methanol and
formic acid were obtained from Merck (Darmstadt, Ger-
many). The water was treated in a Milli-Q water purifica-
tion system (Millipore, Bedford, MA, USA) before use.
2.3.2. HPLC-DAD analytical conditions
Chromatographic separation was achieved as previ-
ously reported (Amaral et al., 2005) with an analytical
HPLC unit (Gilson), using a reversed-phase Spherisorb
ODS2 (250 4.6 mm, 5 lm particle size, Merck, Darms-
tadt, Germany) column. The solvent system used was a
gradient of water/formic acid (19:1) (A) and methanol
(B), starting with 15% methanol and installing a gradient
to obtain 30%B at 15 min, 45%B at 30 min, 52.5%B at
40 min and 100%B at 42 min. The flow rate was
1 ml min
, and the injection volume was 20 ll. Detection
was accomplished with a diode array detector (DAD) (Gil-
son), and chromatograms were recorded at 320 and
350 nm. Spectral data from all peaks were accumulated
in the 200–400 nm range. Data were processed on Uni-
point system software (Gilson Medical Electronics, Villiers
le Bel, France).
Phenolic compounds quantification was achieved by the
absorbance recorded in the chromatograms relative to
external standards, with detection at 320 nm for phenolic
acids and at 350 nm for flavonoids. 3- and 4-Caffeoylquinic
acids were quantified as 5-caffeoylquinic acid, caffeoyltar-
taric acid as caffeic acid, p-coumaric acid derivative and
p-coumaroyltartaric acid as p-coumaric acid, myricetin 3-
hexoside + myricetin derivative as myricetin-rhamnoside,
quercetin 3-hexoside + myricetin derivative as quercetin
3-rhamnoside and kaempferol 3-rhamnoside as kaempferol
3-glucoside. The other compounds were quantified as
2.4. Antioxidant activity
2.4.1. Reagents
BHA (2-tert-butyl-4-methoxyphenol), TBHQ (tert-butyl
hydroquinone) and a-tocopherol were purchased from
Sigma (St. Louis, MO, USA). 2,2-Diphenyl-1-picryl-
hydrazyl (DPPH) was obtained from Alfa Aesar. All other
chemicals were obtained from Sigma Chemical Co. (St.
Louis, USA). Methanol was obtained from Pronalab
(Lisboa, Portugal). Water was treated in a Mili-Q
water purification system (TGI Pure Water Systems,
I. Oliveira et al. / Food Chemistry 105 (2007) 1018–1025 1019
2.4.2. Reducing power assay
The reducing power was determined according to a
described procedure (Oyaizu, 1986). Various concentra-
tions of sample extracts (2.5 ml) were mixed with 2.5 ml
of 200 mmol/l sodium phosphate buffer (pH 6.6) and
2.5 ml of 1% potassium ferricyanide. The mixture was incu-
bated at 50 °C for 20 min. After incubation 2.5 ml of 10%
tricloroacetic acid (w/v) were added and then the mixture
was centrifuged at 1000 rpm in a refrigerated centrifuge
(Centorion K24OR-2003), for 8 min. The upper layer
(5 ml) was mixed with 5 ml of deionised water and 1 ml
of 0.1% of ferric chloride, and the absorbance was mea-
sured spectrophotometrically at 700 nm. The extract con-
centration providing 0.5 of absorbance (EC
) was
calculated from the graph of absorbance registered at
700 nm against the correspondent extract concentration.
BHA and a-tocopherol were used as reference compounds.
2.4.3. Scavenging effect assay
The capacity to scavenge the 2,2-diphenyl-1-picryl-
hydrazyl (DPPH) free radical was monitored according
to a method reported before (Hatano, Kagawa, Yasuhara,
& Okuda, 1988). Various concentrations of sample extracts
(0.3 ml) were mixed with 2.7 ml of methanolic solution
containing DPPH radicals (6 10
mol/l). The mixture
was shaken vigorously and left to stand in the dark until
stable absorption values were obtained. The reduction of
the DPPH radical was measured by monitoring continu-
ously the decrease of absorption at 517 nm. DPPH scav-
enging effect was calculated as percentage of DPPH
discolouration using the equation: % scavenging effect =
]100, where A
is the absorbance
of the solution when the sample extract has been added
at a particular level and A
is the absorbance of the
DPPH solution. The extract concentration providing 50%
inhibition (EC
) was calculated from the graph of scav-
enging effect percentage against extract concentration.
BHA and a-tocopherol were used as reference compounds.
2.4.4. b-Carotene linoleate model system
The antioxidant activity of hazel leaf extracts was eval-
uated according to a described procedure (Mi-Yae, Tae-
Hun, & Nak-Ju, 2003). b-Carotene solution was prepared
by dissolving 2 mg of b-carotene in 10 ml of chloroform.
Two millilitres of this solution were placed in a 100 ml
round-bottom flask. After chloroform removal, at 40 °C
under vacuum, 40 mg of linoleic acid, 400 mg of Tween
80 emulsifier, and 100 ml of distilled water were added to
the flask under vigorous shaking. Aliquots (4.8 ml) of this
emulsion were transferred into different test tubes contain-
ing 0.2 ml of different concentrations of hazel leaf extracts.
The tubes were shaken and incubated at 50 °C in a water
bath. As soon as the emulsion was added to each tube,
the zero time absorbance at 470 nm was measured. Absor-
bance readings were then recorded until the control sample
had changed colour. A blank assay, devoid of b-carotene,
was prepared for background subtraction. Antioxidant
activity was calculated using the following equation: Anti-
oxidant activity = (b-carotene content after 2 h of assay/
initial b-carotene content) 100. The assays were carried
out in triplicate and the results were expressed as mean val-
ues ± standard deviations. The extract concentration pro-
viding 50% antioxidant activity (EC
) was calculated
from the graph of antioxidant percentage against extract
concentration. TBHQ was used as reference compound.
2.5. Antimicrobial activity
2.5.1. Reagents
Ampicillin and cycloheximide were of the highest avail-
able quality, and purchased from Merck (Darmstadt, Ger-
many). Water was treated in a Milli-Q water purification
system (TGI Pure Water Systems, USA).
2.5.2. Microorganisms and culture conditions
Microorganisms CECT were obtained from the Spanish
type culture collection (CECT) of Valencia University,
while microorganisms ESA were clinically isolated strains
identified in Microbiology Laboratory of Escola Superior
´ria de Bragancßa. Gram + (B. cereus CECT 148, B.
subtilis CECT 498 and S. aureus ESA 7 isolated from
pus) and Gram – (E. coli CECT 101, P. aeruginosa CECT
108 and K. pneumoniae ESA 8 isolated from urine) bacte-
ria, and fungi (C. albicans CECT 1394 and C. neofor-
mansESA 3 isolated from vaginal fluid) were used to
screen antimicrobial activity of the three hazel leaves culti-
vars. Microorganisms were cultured aerobically at 37 °C
(Scientific 222 oven model, 2003) in nutrient agar medium
for bacteria, and at 30 °C (Scientific 222 oven model, 2003)
in sabouraud dextrose agar medium for fungi.
2.5.3. Test assays for antimicrobial activity
The screening of antibacterial activities against Gram +
and Gram-bacteria and fungi and the determination of the
minimal inhibitory concentration (MIC) were achieved by
an adaptation of the agar streak dilution method based
on radial diffusion (Hawkey & Lewis, 1994; Ferreira,
Calhelha, Estevinho, & Queiroz, 2004; Sousa et al.,
2006). Suspensions of the microorganism were prepared
to contain approximately 10
cfu/ml, and the plates con-
taining agar medium were inoculated (100 ll; spread on
the surface). Each sample (50 ll) was placed in a hole
(3 mm depth, 4 mm diameter) made in the centre of the
agar. Under the same conditions, different solutions of
ampicillin (antibacterial) and cycloheximide (antifungal)
were used as standards. The assays with the standards were
carried out using DMSO solutions, which was chosen as
the best solvent. After comparative toxicity assays this sol-
vent was shown to be non-toxic. The MIC was considered
to be the lowest concentration of the tested sample able to
inhibit the growth of bacteria or fungi, after 24 h. The
diameters of the inhibition zones corresponding to the
MICs were measured using a ruler, with an accuracy of
0.5 mm. Each inhibition zone diameter was measured three
1020 I. Oliveira et al. / Food Chemistry 105 (2007) 1018–1025
times (three different plates) and the average was consid-
ered. A control using only inoculation was also carried out.
3. Results and discussion
3.1. Phenolic compounds in hazel leaves
The HPLC-DAD analysis of hazel leaves aqueous
extracts (Fig. 1) revealed the presence of several hydroxy-
cinnamic acid and flavonoid derivatives. The three
analysed cultivars exhibited a common qualitative compo-
sition, in which eight phenolic compounds were identified:
3-, 4- and 5-caffeoylquinic acids, caffeoyltartaric acid,
p-coumaroyltartaric acid, myricetin-rhamnoside, quercetin
3-rhamnoside and kaempferol 3-rhamnoside (Fig. 2). In
addition, another p-coumaric acid, three myricetin and
one quercetin derivative were also detected (Fig. 1). All
these compounds were previously reported to occur in
hazel leaves (Amaral et al., 2005), with the exceptions of
4-caffeoylquinic acid and of the unidentified p-coumaric
acid derivative.
The quantification of the phenolics present in the differ-
ent aqueous extracts revealed a high amount of these com-
pounds, ranging from ca. 38 to 44 g/kg, dry basis (Table 1),
which are considerably higher than the values found before
for methanolic extracts of the same and other hazel culti-
vars (Amaral et al., 2005). As observed before, flavonoids
were always the major compounds, varying between 71%
and 80% of total phenolics (Table 1). Cv. M. Bollwiller
showed the highest content of phenolic compounds (Table
All samples exhibited a similar phenolic profile, in which
myricetin-rhamnoside was the major compound, represent-
ing ca. 62.2% of total phenolics (Fig. 3). However, in what
concerns phenolic acids, some quantitative differences were
noticed: in Fertille Coutard leaves the main phenolic acid is
3-caffeoylquinic acid, while in M. Bollwiller and Daviana
cultivars 5-caffeoylquinic and caffeoyltartaric acids are the
major phenolic acid, respectively. Thus, it seems that the
nature of the cultivar influences the phenolic acid composi-
tion. The pair quercetin 3-hexoside plus myricetin deriva-
tive presented the smallest content in all cultivars,
corresponding to ca. 0.9% of total phenolics (Fig. 3).
When comparing the results with those previously
obtained for Fertille Coutard and M. Bollwiller cultivars
(Amaral et al., 2005) it could be noticed that the increase
10 H OH
11 H H
Fig. 1. Chemical structures of identified phenolic compounds from hazel leaves. (1) 3-Caffeoylquinic acid; (2) 4-caffeoylquinic acid; (3) 5-caffeoylquinic
acid; (4) caffeoyltartaric acid; (6) p-coumaroyltartaric acid; (8) myricetin 3-rhamnoside; (10) quercetin 3-rhamnoside; (11) kaempferol 3-rhamnoside.
I. Oliveira et al. / Food Chemistry 105 (2007) 1018–1025 1021
of the total phenolics content is mainly due to an increase
of phenolic acid derivatives contents. This could be attrib-
uted to the environmental factors that allowed an increased
production of these compounds, since samples’ geographi-
cal origin is different from that of the previous work. Nev-
ertheless, this rise could also be partially explained by the
drying process of the samples: in this work the leaves were
dried by lyophilisation, which is faster and less drastic than
the use of a ventilated stove at 30 °C reported before (Ama-
ral et al., 2005), that allows enzymatic reactions, with
possible alteration and loss of compounds. In addition,
3-caffeoylquinic and caffeoyltartaric acids have now been
detected in Fertille Coutard and M. Bollwiller cultivars,
3.2. Antioxidant activity
Although several publications dealing with antioxidant
activity of hazelnut kernel (Alasalvar, Karamaca
¨, Amar-
owicz, & Shahidi, 2006; Duraka et al., 1999; Krings & Ber-
ger, 2001; Moure et al., 2001; Sivakumar & Bacchetta,
2005) and green leafy cover (Alasalvar et al., 2006) have
appeared, no such information is available about antioxi-
dant properties of their leaves. Recently, Sivakumar and
Bacchetta (2005) reported the determination of natural
vitamin E, a potent antioxidant, from Italian hazel leaves
but did not present antioxidant activity studies. In the pres-
ent study, the antioxidant potential of hazel leaves samples
was measured by different biochemical assays: reducing
power, scavenging activity on DPPH radicals and lipid per-
oxidation inhibition by the b-carotene linoleate system.
From the analysis of Fig. 4, we can conclude that the
reducing power of the extracts increased with increasing
concentration and were excellent, presenting high reducing
powers at very low concentrations (<1 mg/ml), and being
even more potent than BHA (A
= 0.12 at 3.6 mg/ml)
and a-tocopherol (A
= 0.13 at 8.6 mg/ml) standards.
The reducing power of the different cultivars was very sim-
ilar and followed the order Fertille Coutard > Daviana
M. Bollwiller.
The scavenging effect of hazel leaves extracts on DPPH
radicals also increased with concentration, specially for
Table 1
Phenolic compounds in hazel leaf samples (mg/kg, dry basis)
Sample Compound
12345678 91011
M. Bollwiller 1241.0 1396.8 3466.1 2939.7 443.5 1551.9 1105.3 26655.9 356.9 3967.0 867.8 43991.9
(10.1) (5.4) (50.6) (41.7) (0.5) (14.5) (23.5) (76.4) (9.6) (27.6) (17.1)
Fertille Coutard 2438.7 1825.3 1442.6 2031.4 741.0 2355.3 642.7 22629.9 303.4 2760.3 545.0 37715.6
(12.5) (13.3) (0.7) (21.8) (0.1) (30.4) (25.8) (400.9) (9.2) (63.8) (7.9)
Daviana 632.7 708.0 1471.0 2480.1 544.9 1802.7 1560.1 25771.1 436.8 2979.5 606.5 38993.4
(7.0) (19.2) (14.6) (1.5) (2.7) (17.8) (12.8) (348.2) (7.3) (27.1) (7.6)
Results are expressed as mean (standard deviation) of three determinations.
(1) 3-Caffeoylquinic acid; (2) 4-caffeoylquinic acid; (3) 5-caffeoylquinic acid; (4) caffeoyltartaric acid; (5) p-coumaric acid derivative; (6) p-couma-
royltartaric acid; (7) myricetin 3-hexoside + myricetin derivative; (8) myricetin 3-rhamnoside; (9) quercetin 3-hexoside + myricetin derivative; (10)
quercetin 3-rhamnoside; (11) kaempferol 3-rhamnoside.
Phenolic compound
Fig. 3. Phenolic compounds profile of hazel leaves. (1) 3-Caffeoylquinic
acid; (2) 4-caffeoylquinic acid; (3) 5-caffeoylquinic acid; (4) caffeoyltartaric
acid; (5) p-coumaric acid derivative; (6) p-coumaroyltartaric acid; (7)
myricetin 3-hexoside + myricetin derivative; (8) myricetin 3-rhamnoside;
(9) quercetin 3-hexoside + myricetin derivative; (10) quercetin 3-rhamno-
side; (11) kaempferol 3-rhamnoside.
Fig. 2. HPLC-DAD of phenolic compounds in hazel leaves (Cv. Fertille
de Coutard). Detection at 320 nm. Peaks: (1) 3-Caffeoylquinic acid; (2)
4-caffeoylquinic acid; (3) 5-caffeoylquinic acid; (4) caffeoyltartaric acid; (5)
p-coumaric acid derivative; (6) p-coumaroyltartaric acid; (7) myricetin 3-
hexoside + myricetin derivative; (8) myricetin 3-rhamnoside; (9) quercetin
3-hexoside + myricetin derivative; (10) quercetin 3-rhamnoside; (11)
kaempferol 3-rhamnoside.
1022 I. Oliveira et al. / Food Chemistry 105 (2007) 1018–1025
concentrations below 0.5 mg/ml (Fig. 5). Fertille Coutard
and M. Bollwiller cultivars showed the highest and the low-
est activities, respectively, being the obtained results much
better than those obtained for BHA (96% at 3.6 mg/ml)
and a-tocopherol (95% at 8.6 mg/ml). For all the tested
hazel cultivars DPPH scavenging activity values were
higher than 93.1% at 0.5 mg/ml. These results are much
better than DPPH radical scavenging effects described in
the literature (Moure et al., 2001) for methanol extracts
from hazel fruits (14.2% at 2 mg/mL). Nevertheless, etha-
nol extract from hazelnut was reported as possessing higher
radical scavenging effects than other roasted foods such as
almond (Krings & Berger, 2001).
The antioxidant activity of hazel leaves extracts mea-
sured by the bleaching of b-carotene is shown in Fig. 6.
The results obtained indicated a concentration-dependent
antioxidant capacity, following the order Fertille Cou-
tard > Daviana > M. Bollwiller which presented values at
2 mg/ml of 61.3%, 51.3% and 50.3%, respectively. It is
probable that the antioxidative components in the extracts
can reduce the extent of b-carotene destruction by neutral-
izing the linoleate free radical and other free radicals
formed in the system (Mi-Yae et al., 2003). The protection
of b-carotene bleaching provided by TBHQ standard
reached 82.2% at 2 mg/ml and was slightly more efficient
than the samples. Nevertheless, this and other synthetic
antioxidants applied in fat and oily foods to prevent oxida-
tive deterioration were found to be anticarcinogenic as well
as carcinogenic in experimental animals (Loliger, 1991).
For an overview of the results, at Table 2 there are pre-
sented the EC
values for the antioxidant activity assays
obtained from each hazel leaves sample. Fertille Coutard
cultivar revealed better antioxidant properties (lower
values) than the other samples, for all the biochemical
assays used in the antioxidant activity screening. The EC
values obtained for reducing power and scavenging effects
on DPPH radicals (<0.3 mg/ml) were better than for
b-carotene bleaching inhibition (>1.2 mg/ml).
3.3. Antimicrobial activity
The antimicrobial capacity of phenolic compounds, in a
general way, is well-known (Pereira et al., 2006; Proestos
et al., 2005; Puupponen-Pimia
¨et al., 2001; Rauha et al.,
2000; Zhu et al., 2004) and we propose, for the first time,
the use of hazel leaves extracts as a source of antimicrobi-
als. As previously described, individual phenolic com-
pounds present in the hazel leaves extracts were identified
and quantified, but we choose to submit the entire extracts
to antimicrobial activity studies. In fact, food extracts may
be more beneficial than isolated constituents, since a bioac-
tive individual component can change its properties in the
presence of other compounds present in the extracts (Bor-
chers, Keen, & Gerstiwin, 2004). The minimal inhibitory
concentration (MIC) values for bacteria (B. cereus,B. sub-
tilis,S. aureus,E. coli,P. aeruginosa, K. Pneumoniae) and
fungi (C. albicans and C. neoformans) were determined as
an evaluation of the antimicrobial activity of the hazel sam-
ples and were presented in Table 3.
The tested samples revealed antimicrobial activity
against all the microorganisms apart from P. aeruginosa
0.4 0.6 0.8 1
Concentration (mg/ml)
Abs at 700 nm
Bollwiller Fertille de Coutard Daviana
Fig. 4. Reducing power values of different cultivars of hazel leaf extracts.
Each value is expressed as mean ± standard deviation.
0 0.2 0.4 0.6 0.8 1
Concentration (mg/ml)
Scavenging Effect (%)
Bollwiller Fertille de Coutard Daviana
Fig. 5. Scavenging effect on DPPH of different cultivars of hazel leaf
extracts. Each value is expressed as mean ± standard deviation.
Concentration (mg/ml)
Antioxidant activity (%)
Bollwiller Fertille de Coutard Daviana
Fig. 6. Antioxidant activity (%) by b-carotene bleaching method of
different cultivars of hazel leaf extracts. Each value is expressed as
mean ± standard deviation.
Table 2
values (mg/ml) of hazel leaf samples
Samples Reducing
power (EC
bleaching (EC
M. Bollwiller 0.224 0.203 1.981
Fertille Coutard 0.199 0.164 1.243
Daviana 0.223 0.188 1.861
I. Oliveira et al. / Food Chemistry 105 (2007) 1018–1025 1023
and C. albicans, which were resistant to the extracts at a
concentration of 100 mg/ml. M. Bollwiller cultivar proved
to be the most promising hazel cultivar to inhibit microbial
growth, presenting lower MICs and higher growth inhibi-
tion zones. Gram positive bacteria were more susceptible
than either Gram negative bacteria or fungi, presenting
MICs of 0.1 mg/ml for B. cereus and S. aureus, and
1 mg/ml for B. subtilis. These results are of a great impor-
tance particularly in the case of S. aureus which is well-
known for being resistant to a number of phytochemicals
and for the production of several types of enterotoxins that
cause gastroenteritis (Halpin-Dohnalek & Marth, 1989).
The antifungicide activity of the hazel leaves was weak,
being C. albicans resistant to all the samples and C. neofor-
mans susceptible only to samples from M. Bollwiller culti-
var but in a high concentration (100 mg/ml). Nevertheless,
the MIC values obtained for these extracts were even better
than the results obtained by us in previous works with table
olives (Pereira et al., 2006) and ‘‘alcaparras(Sousa et al.,
In conclusion, the results obtained in this study demon-
strate that hazel leaves may be a good candidate for
employment as antimicrobial agent against bacteria
responsible for human gastrointestinal and respiratory
tract infections. It may also constitute a good source of
healthy compounds, namely phenolic compounds, suggest-
ing that it could be useful in the prevention of diseases in
which free radicals are implicated.
The authors are grateful to INTERREG III A Program,
Project PIREFI for financial support of this work.
Alasalvar, C., Karamaca
¨, M., Amarowicz, R., & Shahidi, F. (2006).
Antioxidant and antiradical activities in extracts of hazelnut kernel
(Corylus avellana L.) and hazelnut green leafy cover. Journal of
Agriculture and Food Chemistry, 54, 4826–4832.
Amaral, J. S., Ferreres, F., Andrade, P. B., Valenta
˜o, P., Pinheiro, C.,
Santos, A., et al. (2005). Phenolic of hazel (Corylus avellana L.)
leaves cultivars grown in Portugal. Natural Product Research, 19,
´s, H., Ferna
´ndez, B., Rodrı
´guez, R., & Rodrı
´guez, A. (2002).
Phytohormone contents in Corylus avellana and their relationship to
age and other developmental processes. Plant Cell, Tissue and Organ
Culture, 70, 173–180.
Barriada-Pereira, M., Gonza
´lez-Castro, M. J., Muniategui-Lorenzo, S.,
´a, P., Prada-Rodrı
´guez, D., & Ferna
´ndez, E.
(2004). Determination of 21 organochlorine pesticides in tree leaves
using solid-phase extraction clean-up cartridges. Journal of Chroma-
tography A, 1061, 133–139.
Borchers, A. T., Keen, C. L., & Gerstiwin, M. E. (2004). Mushrooms,
tumors, and immunity: An update. Experimental Biology and Medi-
cine, 229, 393–406.
Bousquet, L., Lache
´rade, S., Jacquemoud, S., & Moya, I. (2005). Leaf
BRDF measurements and model for specular and diffuse components
differentiation. Remote Sensing of Environment, 98, 201–211.
Duraka, I., Koksalb, I., Kacßmaz, M., Buyukkocßak, S., C¸ imen, B. M. Y.,
& Ozturk, H. S. (1999). Hazelnut supplementation enhances plasma
antioxidant potential and lowers plasma cholesterol levels. Clinica
Chimica Acta, 284, 113–115.
Ferreira, I. C. F. R., Calhelha, R. C., Estevinho, L. M., & Queiroz, M.-J.
R. P. (2004). Screening of antimicrobial activity of diarylamines in
the 2,3,5-trimethylbenzo[b]thiophene series: A structure–activity eval-
uation study. Bioorganic and Medicinal Chemistry Letter, 14,
Fraisse, D., Carnat, A., Carnat, A. P., & Lamaison, J. L. (1999).
Standardization of hazel leaf. Annales Pharmaceutiques Francßaises, 57,
Halpin-Dohnalek, M. I., & Marth, E. H. (1989). Growth and production
of enterotoxin A by Staphylococcus aureus in cream. Journal of Dairy
Science, 72, 2266–2275.
Hatano, T., Kagawa, H., Yasuhara, T., & Okuda, T. (1988). Two new
flavonoids and other constituents in licorice root: Their relative
astringency and scavenging effects. Chemical and Pharmaceutical
Bulletin, 36, 2090–2097.
Hawkey, P. M., & Lewis, D. A. (1994). Medical bacteriology – A practical
approach. UK: Oxford University (pp. 181–194).
Howsam, M., Jones, K. C., & Ineson, P. (2000). PAHs associated with the
leaves of three deciduous tree species. I – Concentrations and profiles.
Environmental Pollution, 108, 413–424.
Howsam, M., Jones, K. C., & Ineson, P. (2001). PAHs associated with the
leaves of three deciduous tree species. II: Uptake during a growing
season. Chemosphere, 44, 155–164.
Krings, U., & Berger, R. G. (2001). Antioxidant activity of some roasted
foods. Food Chemistry, 72, 223–229.
Loliger, J. (1991). The use of antioxidants in foods. In Free radicals and
food additives (pp. 121–150). London: Taylor & Francis.
Mi-Yae, S., Tae-Hun, K., & Nak-Ju, S. (2003). Antioxidants and free
radical scavenging activity of Phellinus baumii (Phellinus of Hymeno-
chaetaceae) extracts. Food Chemistry, 82, 593–597.
Moure, A., Franco, D., Sineiro, J., Domı
´nguez, H., Nu
˜ez, M. J., &
Lema, J. M. (2001). Antioxidant activity of extracts from Gevuina
Table 3
Antimicrobial activity of hazel leaf extracts
MIC (mg/ml)
Cultivar B. cereus B. subtilis S. aureus P. aeruginosa E. coli K. pneumoniae C. albicans C. neoformans
M. Bollwiller 0.1 1 0.1 100 50 1 100 100
(++++) (++++) (++) (–) (++++) (++) (–) (++++)
Fertille 0.1 1 0.1 100 100 10 100 100
Coutard (++) (+++) (++++) (–) (–) (++++) (–) (–)
Daviana 0.1 1 0.1 100 100 50 100 100
(++) (++) (++) (–) (++++) (++++) (–) (–)
No antimicrobial activity (–), inhibition zone < 1 mm. Slight antimicrobial activity (+), inhibition zone 2–3 mm. Moderate antimicrobial activity (++),
inhibition zone 4–5 mm. High antimicrobial activity (+++), inhibition zone 6–9 mm. Strong antimicrobial activity (++++), inhibition zone > 9 mm.
Standard deviation ± 0.5 mm.
1024 I. Oliveira et al. / Food Chemistry 105 (2007) 1018–1025
avellana and Rosa rubiginosa defatted seeds. Food Research Interna-
tional, 34, 103–109.
Oyaizu, M. (1986). Studies on products of browning reactions: Antiox-
idative activities of products of browning reaction prepared from
glucosamine. Japanese Journal of Nutrition, 44, 307–315.
Pereira, J. A., Pereira, A. P. G., Ferreira, I. C. F. R., Valenta
˜o, P.,
Andrade, P. B., Seabra, R., et al. (2006). Table olives from Portugal:
Phenolic compounds, antioxidant potential and antimicrobial activity.
Journal of Agriculture and Food Chemistry, 54, 8425–8431.
Proestos, C., Chorianopoulos, N., Nychas, G.-J. E., & Komaitis, M.
(2005). RP-HPLC analysis of the phenolic compounds of plant
extracts. Investigation of their antioxidant capacity and antimicro-
bial activity. Journal of Agriculture and Food Chemistry, 53, 1190–
¨, R., Nohynek, L., Meier, C., Ka
¨nen, M., Heinonen,
M., Hopia, A., et al. (2001). Antimicrobial properties of phenolic
compounds from berries. Journal of Applied Microbiology, 90,
Rauha, J.-P., Remes, S., Heinonen, M., Hopia, A., Ka
¨nen, M.,
Kujala, T., et al. (2000). Antimicrobial effects of Finnish plant extracts
containing flavonoids and other phenolic compounds. International
Journal of Food Microbiology, 56, 3–12.
Rey, M., Dı
´az-Sala, C., & Rodrı
´guez, R. (1998). Free polyamine content
in leaves and buds of hazelnut (Corylus avellana L. cv. Negret) trees
subjected to repeated severe pruning. Scientia Horticulturae, 76,
Seabra, R. M., Andrade, P. B., Valenta
˜o, P., Fernandes, E., Carvalho, F.,
& Bastos, M. L. (2006). Anti-oxidant compounds extracted from
several plant materials. In M. Fingerman & R. Nagabhushanam
(Eds.), Biomaterials from Aquatic and Terrestrial organisms
(pp. 115–174). Enfield (New Hampshire): Science Publishers.
Sivakumar, G., & Bacchetta, L. (2005). Determination of natural vitamin
E from Italian hazelnut leaves. Chemistry of Natural Compounds, 41,
Sousa, A., Ferreira, I. C. F. R., Calhelha, R., Andrade, P. B., Valenta
˜o, P.,
Seabra, R., et al. (2006). Phenolics and antimicrobial activity of
traditional stoned table olives ‘‘alcaparra.Bioorganic and Medicinal
Chemistry, 14, 8533–8538.
Stams, A. J. M., & Lutke Schipholt, I. J. (1990). Nitrate accumulation in
leaves of vegetation of a forested ecosystem receiving high amounts of
atmospheric ammonium sulphate. Plant and Soil, 125, 143–145.
Valnet, J. (1992). Phytothe
´rapie: Traitement des maladies par les plantes
(sixth ed.). Paris: Maloine (pp. 473–475).
Vaughan, J. G., & Geissler, C. A. (1997). The New Oxford Book of Food
Plants. New York: Oxford University Press (pp. 30–31).
Zhu, X., Zhang, H., & Lo, R. (2004). Phenolic compounds from the leaf
extract of artichoke (Cynara scolymus L.) and their antimicrobial
activities. Journal of Agriculture and Food Chemistry, 52, 7272–7278.
I. Oliveira et al. / Food Chemistry 105 (2007) 1018–1025 1025
... g/kg, dry basis) were found to be dominant phenolics (Amaral et al., 2005). The same phenolics, plus 3-caffeoylquinic, and caffeoyltartaric acids were reported in Corylus avellana (Fertille Coutard, Daviana, and M. Bollwiller cultivars) by Oliveira et al. (2007). The researchers also examined the antioxidant and antimicrobial activities of hazelnut tree leaves. ...
... It was found that they inhibited more than 93.1% of DPPH at 0.5 mg/ml concentration compared to BHA (96% at 3.6 mg/ml) and α-tocopherol (95% at 8.6 mg/ml). It has an antimicrobial effect against Bacillus cereus, Bacillus subtilis, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumoniae, but not toward Candida albicans and, Cryptococcus neoformans (only cultivar M. Bollwiller was effective at 100 ml/mg) (Oliveira et al., 2007). Riethmuller et al. (2013) evaluated the effect of methanol and ethyl acetate solvents on their bioactive compounds the leaves of C. avellana L. Among their bioactive compounds, six flavonoid glycosides (myricetin-3-O-hexoside, ...
Nowadays, increasing sensitivity to the environment leads to the development of sustainable agricultural policies. In this respect, it has become important to transform agricultural waste products into value-added products. Hazelnut, which has a significant trade volume worldwide, is processed into products, and some waste materials can be emerge. These waste products could transform into high added-value to food, cosmetics, and pharmaceutical industries due to possessing the bioactive compounds such as phenolics and, dietary fibre in them. This review represents the research on the bioactive compounds from the hazelnut waste, especially conducted in recently, and concentrates on its tree leaf, husk, and oil meal.
... Günümüzde doğal antimikrobiyal maddelere olan ilgi her geçen gün artmaktadır. Bunun en önemli sebebi kimyasal katkılardan kaçıma düşüncesiyle olan tüketici baskısıdır (Oliveira et al., 2007;Cowan, 1999). ...
Full-text available
zet Bu çalışmada iki farklı ceviz türünü dış kabukları su, etanol ve metanolle ekstrakte edilmiş ve daha sonra ekstraktların toplam fenolik madde içerikleri antioksidan aktiviteleri (DPPH ve İndirgeyici güç) belirlenmiştir. Buna göre ceviz dış kabukların biyoaktivitesi yüksek bir materyal olduğu sonucuna varılmıştır. Ayrıca etanol ve metanolden elde edilen ekstraktların sudan elde edilen ekstraktlara göre daha antioksidan ve fenolik madde potansiyellerinin daha iyi olduğu gözlemlenmiştir. Abstract In this study two different types of walnut husks extracted by water, ethanol and methanol and total phenolic content and then antioxidant activity (DPPH and reducing power) of these extracts were determined. Accordingly, walnut shell was concluded that a material having a high bioactivity. Also ethanol and methanol extracts have more phenolic material and antioxidan activity potential than water extract.
... Antimicrobial agents such as chlorohexidine have been recommended by evidence in highrisk individuals for dental caries (2). Recently, natural products have gained increasing popularity in health industries (3,4). Iran is the third producer of walnuts in the world (5).Walnut green husk (WGH), as an agricultural waste, is considered a low-cost source for preparing Juglone (5 hydroxy-1,4 Naphthoquinone) (6). ...
Background: Chemical agents, such as Chlorhexidine are used as one of dental plaque control strategy. Researchers are looking for a natural and economic substitute with same antibacterial efficacy and less complications. The aim of this study was to evaluate the antimicrobial efficacy of the Khorasan Razavi walnut green husk (WGH) extract with and without adding ZnO nanoparticles (nZnO) on Streptococcus mutans (S. mutans). Methods: In this in vitro study, antimicrobial effect of the Hydro-ethanolic extract of WGH, was evaluated against S. mutans. Broth Dilution and Agar diffusion methods were used with 90 tubes containing different dilutions of WGH extract (100 to 0.006 mg/ml). ZnO nanoparticles (nZnO) were added to 45 tubes. Streptococcus mutans was exposed to 15 different serial concentrations of study extracts, from 100 mg/ml to 0.006 mg/ml. Minimum inhibitory concentration (MIC) of the study extracts were determined and zone of inhibition diameter was compared to positive controls (chlorhexidine 0.2%, nZnO), and negative control (sterile distilled water). The differences between the mean diameters, were analyzed by independent sample T- teS. Results: Minimum inhibitory concentration (MIC) of study extract was found to be 50mg/mL, with adding nZnO, MIC was reduced to 3.12mg/mL. Mean diameter of inhibition zone at 3.12 mg/ml with and without adding ZnO nanoparticles were 17.67±0.57 mm and 8±0.001 mm, respectively, (p-value< 0.001). Discussion: Adding nZnO could be enhanced antimicrobial efficacy of the WGH extract against S. mutants, while it was still less effective than chlorhexidine.
... Conversely, some Gram-negative bacteria (Escherichia coli, K. pneumoniae, Pseudomonas aeruginosa) were not inhibited [94]. Bacillus cereus and S. aureus were also very sensitive to boiling water extract of hazel leaves at the same concentration, while B. subtilis was inhibited at a higher concentration (1 mg mL −1 ), and again Gram-negative species displayed much lower sensitivity, with P. aeruginosa resistant even at 100 mg mL −1 [95]. ...
Full-text available
Citation: Nicoletti, R.; Petriccione, M.; Curci, M.; Scortichini, M. Hazelnut-Associated Bacteria and
... Conversely, some Gram-negative bacteria (Escherichia coli, K. pneumoniae, Pseudomonas aeruginosa) were not inhibited [94]. Bacillus cereus and S. aureus were also very sensitive to boiling water extract of hazel leaves at the same concentration, while B. subtilis was inhibited at a higher concentration (1 mg mL −1 ), and again Gram-negative species displayed much lower sensitivity, with P. aeruginosa resistant even at 100 mg mL −1 [95]. ...
Full-text available
In recent years, the cultivation of hazelnut (Corylus avellana) has expanded in several areas of Europe, Asia, Africa, and North and South America following the increased demand for raw materials by the food industry. Bacterial diseases caused by Xanthomonas arboricola pv. corylina and Pseudomonas avellanae are threats of major concern for hazelnut farmers. These pathogens have been controlled with copper-based products, which are currently being phased out in the European Union. Following the need for alternative practices to manage these diseases, some progress has been recently achieved through the exploitation of the plant’s systemic acquired resistance mechanisms, nanoparticle technology, as well as preventive measures based on hot water treatment of the propagation material. However, bacteria are not only agents of the biotic adversities of hazelnut. In fact, the application of plant growth-promoting rhizobacteria at the seedling level could enhance better performance of the tree. Likewise, endophytic and epiphytic microorganisms are considered to play a notable role in plant nutrition and protection, and their effects on hazelnut fitness deserve to be further investigated. Finally, bacterial associations may also be relevant in the post-harvest phase, particularly with reference to the processes of lipid oxidation and fat degradation suffered by the kernels after grinding.
... Gosling (2007) indicated an optimal cold stratification protocol for The seeds are usually classified as recalcitrant or suborthodox, as are not reliably stored for more than 1 year under ambient conditions without losing viability on drying (Hamid, 2014), yet this classification is not absolute as the seeds can survive a level of desiccation. Michalak et al. (2013) found no significant effect of desiccation on the germination success of C. avellana, across a water content range of 0.027-0.13 ...
Full-text available
This account presents information on all aspects of the biology of Corylus avellana L. (Hazel) that are relevant to understanding its ecological characteristics and behaviour. The main topics are presented within the standard framework of the Biological Flora of Britain and Ireland : distribution, habitat, communities, responses to biotic factors, responses to environment, structure and physiology, phenology, floral and seed characters, herbivores and disease, history and conservation. Wild C. avellana in Britain and Ireland grows in a wide climatic and ecological range, in a broad suite of vegetation communities, particularly woodlands, at all latitudes and from 0 to 650 m asl. It supports a large number of faunal and fungal associates. The developing plant sends up basal shoots every spring from the peripheral parts of its underground stool, which gives it a structural regenerative advantage over cohabitant woody species. The flowers and pollen of C. avellana are adapted for wind pollination, yet honeybees have been observed to gather its pollen. The pollen and fruit of C. avellana are a cause of allergic reactions in sensitive people, with previous exposure to Birch pollen a strong predictor of the food allergy. Corylus avellana is native to Europe and western Asia, and was one of the first plant species to recolonize Europe after the last gIacial period. By the time of its cultivation in the Roman empire, regional human‐selected lineages of C. avellana were already developing, with independent domestication in the western and eastern Mediterranean. Corylus avellana is a genetically diverse taxon with effective gene flow across populations, presenting a continuum of wild to domesticated plants. Its nuts and involucres show a wide morphological variability, with hundreds of cultivars and forms proposed. The taxon Corylus maxima Mill. is sympatric and fully fertile with C. avellana , yet rarely self‐sown and their hybrid is little recorded in Britain and Ireland. Independent molecular studies have concluded that specimens of C. maxima cluster with C. avellana . Hazelnuts are globally one of the most important nut crops, currently with 70% of traded nuts being grown in Türkiye, followed by Italy and Azerbaijan.
In the present study, total antioxidant activity (TAC), phenolic compound amounts (TPC) and reducing power (RP) of hazelnut leaves collected from Giresun were investigated. Antioxidant levels were determined in the water extracts of hazelnut leaves by using methods according to the appropriate literature. In the results obtained from water extracts at three different doses (1, 2.5 and 5 mg/kg), it was determined that the total antioxidant capacity was high depending on the dose and phenolic content. The high antioxidant capacity of hazelnuts produced in humid regions in our country also depends on the phenolic substance content it has. As can be seen from the results, the phenolic content also increased depending on the dose. In line with all these data, we believe that it can be a precursor to many biological studies.
Full-text available
Bu çalışmada ceviz (Juglans regia) yapraklarının su, etil asetat ve metanol ekstrelerinin antibiyofilm aktivitesi araştırılmıştır. Ekstrelerin antimikrobiyel ve antibiyofilm aktivitesi Pseudomonas aeruginosa, Klebsiella pneumoniae, Aeromonas hydrophila ve Salmonella enterica, Staphylococcus warneri, Staphylococcus capitis, Staphylococcus aureus, Enterococcus faecium, E. faecalis, Listeria monocytogenes Serovar I, L. monocytogenes 19111, L. monocytogenes 4b 19115, L. ivanovii 19119, L. innocua 6a 33090, Streptococcus mutans, S. anginosus, Bacillus cereus, Bacillus safensis ve B. mojavensis’a karşı araştırılmıştır. Bütün ekstrelerinin S. mutans (1a103), S. mutans (2a7) ve S. aureus (GMC7) üzerinde antimikrobiyel aktivitesinin olmadığı diğer bakteriler üzerinde ise farklı oranlarda etki gösterdikleri belirlenmiştir. Su ekstresinin %99.20 metanol ekstresinin %95.05 ve etil asetat ekstresinin ise %95.22 oranlarına varan antibiyofilm etkilerinin olduğu tespit edilmiştir. Ekstrelerin biyofilm oluşumunu azaltmada oluşmuş biyofilmi gideriminden daha etkili oldukları tespit edilmiştir. Ayrıca en yüksek antioksidan aktiviteye etil asetat aktivitesinin sahip olduğu belirlenmiştir.
As output of hazelnut increases worldwide, so does the amount of by-products, leading to huge waste and environmental stress. This paper focuses on the varieties of hazelnut that have been studied more in the past two decades, and summarizes the research status of hazelnut and its by-products from the aspects of nutritional value, phytochemicals, extraction methods, biological functions and applications. Hazelnut and its by-products are rich in a variety of bioactive constituents, mainly polyphenols, which have antioxidant, antibacterial and prebiotic effects. Moreover, hazelnut shells, husks, and leaves contain taxanes such as paclitaxel, which can inhibit the proliferation of cancer cells. They are potentially good natural sources of paclitaxel compared to the slower growing yew. Therefore, it is essential to further integrate the extraction techniques and health-promoting properties of these nutrients and bioactive substances to expand their application and enhance their value.
Full-text available
Fındık (Corylus avellana L.), ekonomik değeri yüksek, küresel üretimi önemli olan bir üründür. Ancak fındık yaprakları ile ilgili çalışmalar bugüne kadar sınırlı kalmıştır. Bu çalışmada, Giresun’un iki ayrı bölgesinden toplanan üç çeşit (yağlı, (tombul), sivri ve ham) fındık ağacı yaprağı infüzyon yöntemi ile ekstrakte edilmiştir. Analiz öncesinde ekstraktların glove box içerisinde buharlaştırılması ve örneklerin hazırlanması bu çalışmanın en kritik noktalarından birisidir. Ekstraktlarda fenolik bileşiklerin miktarları, toplam fenolik madde miktarı ve antioksidan aktivitelerinin belirlenmesi amaçlanmıştır. Fenolik bileşiklerin tayini Sıvı Kromatografi - Kütle Spektroskometri (LC-MS/MS) ile ve toplam fenolik miktarı ise Folin-Ciocâlteu yöntemi ile belirlenmiştir. Antioksidan aktivite, 2,2-azino-bis(3etilbenzo-tiazolin-6-sülfonik asit (ABTS•+), 2,2-difenil-1-pikrilhidrazil (DPPH•) radikal temizleme aktiviteleri ve demir (III) indirgeme / antioksidan güç (FRAP) yöntemleri ile test edilmiştir. Espiye Merkez’den toplanan tombul fındık ağacı yaprağı (TFE) ekstraktı en yüksek ABTS•+ radikal temizleme (SC50: 0.00023±3.9E-06 mg mL-1) ve FRAP (882.75±8.24 µM TEAC (Trolox Eşdeğer Antioksidan Kapasitesi) antioksidan aktivitesi sergiledi. Ayrıca, Espiye Merkez’den toplanan ham fındık ağacı yaprağı (HFE) (SC50: 0.00033±1.3E-06 mg mL-1) ve tombul fındık ağacı yaprağı (TFE) (SC50: 0.00034±1.7E-06 mg mL-1) ekstraktları hemen hemen aynı DPPH• temizleme aktivitesi sergiledi. TFE ekstraktı en yüksek toplam fenolik içeriğe (163.33±4.36 GAE (Gallik Asit Eşdeğeri) µg mL-1 ve 228.67±6.11 KE (Kateşin Eşdeğeri) µg mL-1) sahipti. Analizlenen yapraklarda gallik asit, kateşin, epikateşin, taksifolin, elajik asit, kuersetin ve kafeik asit tespit edilmiştir. Giresun’dan toplanan tombul fındık yapraklarında (TFG) ve sivri fındık yapraklarında (SFY) kateşin miktarları sırasıyla 192.05±1.74 ve 367.63±2.6 µg g-1 olarak bulunmuştur.
Full-text available
Chilean hazelnuts (Gevuina avellana Mol) and mosqueta rose (Rosa aff. Rubiginosa L.) meals were extracted with methanol, ethanol, acidified water, acetone, butanol, diethyl ether and ethyl acetate. Ethanol and methanol extracted the highest amount of soluble substances from both seed meals. The highest concentration of total polyphenols was found in the ethanolic extracts, although that of acetone from R. rubiginosa presented similar values. The antioxidant activity of the extracts evaluated by the β-carotene assay and with as hydrogen radical scavenging ability showed that the activity of the butanol and methanol extracts from G. avellana was comparable to those of synthetic antioxidants butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT). The 2,2,-diphenyl-1-picrylhydrazyl radical (DPPH) radical scavenging activity of the G. avellana methanol, ethanol and water extracts was 2–3 times lower than those of BHT and BHA, respectively. The activity of R. rubiginosa extracts ranged from that of BHT for the water extracts to 80% inhibition in respect to control achieved with the ethanol extracts.
Products of browning reaction of glucosamine were prepared from glucosamine-HCl by incubating it at 37°C for 0-30 days, and the antioxidative activity, reducing power, degree of browning, aminosugar contents, pH, moisture and total nitrogen contents of the products were measured. In addition, the brown products prepared from glucosamine by incubation at 37°C for 0, 15 and 30 days were fractionated by gel filtration using Sephadex G-15, and the antioxidative activity, reducing power, degree of browning and pH of each fraction were also measured. The results obtained were as follows: 1) When white powder of free glucosamine was allowed to stand for 3 days at 37°C, it transformed to a brown paste. 2) The strongest antioxidative activity was observed in the product obtained after incubation between 20 and 30 days. 3) The increase in antioxidative activity of the products of browning reaction was accompanied by the increase in the degree of browning. 4) The brown products prepared from glucosamine by long incubation were fractionated into fractions according to their molecular weights. Antioxidative activity was detected in the fractions corresponding to intermediate molecular weight.
The antioxidative potential of ethanolic extracts from roasted wheat germ was compared with extracts from other roasted food. Among the cereal products, roasted wheat germ and roasted press cake from wheat germ processing yielded the most efficient extracts when added to stripped maize oil under accelerated-oxidation conditions. Ground and roasted hazelnut and sweet almond, respectively, showed comparable protective effects in stripped maize oil. In the same model system, an ethanolic extract of commercial coffee suppressed lipid oxidation almost completely. Radical scavenging effects of some extracts were analysed using the bleaching of the stable 1,1-diphenyl-2-picrylhydrazyl radical (DPPH). The results were not in full agreement with those obtained in the accelerated oxidation experiments using stripped maize oil.
Vegetation of an acid woodland, receiving an atmospheric ammonium input of about 3 kmol (40 kg N) per hectare per year, was analyzed on the content of organic nitrogen, ammonium and nitrate. A high nitrate content (50–320 μmol g−1 dry weight) was found in bird-cherry, black-berry and bracken, whereas only low amounts (up to 2 μmol g−1 dry weight) of nitrate were present in mountain-ash, hazel and the two dominant tree species oak and birch. The impact of this nitrate uptake and nitrate accumulation on soil pH and autotrophic nitrification is discussed.
Endogenous levels of indole-3-acetic acid, abscisic acid, and cytokinins (Z-type: dihydrozeatin, dihydrozeatin riboside, zeatin, and zeatin riboside; iP-type: N 6-isopentenyl adenine and N 6-isopentenyl adenosine), were determined in leaves of hazelnut (Corylus avellana L.) (adult material from spring, autumn and forced outgrowth, and juvenile material). Our results showed high levels of indole-3-acetic acid, abscisic acid and total cytokinins in spring samples and low levels of the same hormones in autumn and forced outgrowth materials. The ratios of iP-type/Z-type cytokinins were low in autumn and spring leaves, while they were high in the juvenile and forced outgrowth samples. Both juvenile and forced-outgrowth hazel tissues also showed a high morphogenetic potential, suggesting that the ratio of iP-type/Z-type cytokinins may be a good index of in vitro potential of hazelnut materials.
A new potential source of natural vitamin E from thirteen samples of Corylus avellana L. leaves was screened: the major Italian cultivar — Tonda romana (collected from Latium and Sardinia localities); ten local genotypes from Sardinia — Moro seme, Suconcale, Moro, Sarda grossa, Sarda grossa seme, Sarda schiacciata, Coccoredda, Sarda lunga, Sarda piccola and Sarda tardiva; wild genotype — Selvatico from Latium. The determination was performed after optimizing the high-efficiency pressurized liquid extraction (PLE) conditions of α-tocopherol from Italian hazelnut tree green leaves. Moro from Sardinia showed the highest content of α-tocopherol (237.4±0.3 µg/g d.w). Leaves of this genotype may be considered as a potential new source for natural α-tocopherol.
This study was carried out to expand the utilization (for the pharmaceutical and food industries) of extracts of Phellinus baumii. Fractions rich in phenolics were extracted from P. baumii using various solvents. Antioxidant and free radical scavenging activity were studied using a β-carotene-linoleate model system and reactive oxygen species generation system. Total phenolic compounds in methanol and hot water extracts were 33.3 and 20.7 mg/100 ml, respectively; these values are higher than other solvent extracts. Therefore, methanol and hot water extracts exhibited good inhibition rates, of about 80–90%, by hydroxyl radical scavenging activity, hydrogen peroxide scavenging activity, effect of reducing power on metallic compound formation and antioxidant activity.