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Arbutus unedo L.: Chemical and Biological Properties

Abstract and Figures

Arbutus unedo L. (strawberry tree) has a circum-Mediterranean distribution, being found in western, central and southern Europe, north-eastern Africa (excluding Egypt and Libya) and the Canary Islands and western Asia. Fruits of the strawberry tree are generally used for preparing alcoholic drinks (wines, liqueurs and brandies), jams, jellies and marmalades, and less frequently eaten as fresh fruit, despite their pleasing appearance. An overview of the chemical composition of different parts of the plant, strawberry tree honey and strawberry tree brandy will be presented. The biological properties of the different parts of A. unedo and strawberry tree honey will be also overviewed.
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Molecules 2014, 19, 15799-15823; doi:10.3390/molecules191015799
molecules
ISSN 1420-3049
www.mdpi.com/journal/molecules
Review
Arbutus unedo L.: Chemical and Biological Properties
Maria G. Miguel 1,*, Maria L. Faleiro 1,2, Adriana C. Guerreiro 1 and Maria D. Antunes 1
1 IBB-Centro de Biotecnologia Vegetal, Faculdade de Ciências e Tecnologia,
Universidade do Algarve Edif. 8, Campus de Gambelas, Faro 8005-139, Portugal
2 IBB-Centro de Biomedicina Molecular e Estrutural, Faculdade de Ciências e Tecnologia,
Universidade do Algarve, Edif. 8, Campus de Gambelas, Faro 8005-139, Portugal
* Author to whom correspondence should be addressed; E-Mail: mgmiguel@ualg.pt;
Tel.: +351-289-800-900 (ext. 7634); Fax: +351-289-818-419.
External Editor: Derek J. McPhee
Received: 21 July 2014; in revised form: 22 September 2014 / Accepted: 22 September 2014 /
Published: 30 September 2014
Abstract: Arbutus unedo L. (strawberry tree) has a circum-Mediterranean distribution,
being found in western, central and southern Europe, north-eastern Africa (excluding Egypt
and Libya) and the Canary Islands and western Asia. Fruits of the strawberry tree are
generally used for preparing alcoholic drinks (wines, liqueurs and brandies), jams, jellies
and marmalades, and less frequently eaten as fresh fruit, despite their pleasing appearance.
An overview of the chemical composition of different parts of the plant, strawberry tree
honey and strawberry tree brandy will be presented. The biological properties of the
different parts of A. unedo and strawberry tree honey will be also overviewed.
Keywords: strawberry tree; plant parts; chemical composition; biological properties;
honey; brandy
1. Introduction
Arbutus L. is a genus that belongs to the Vaccionioideae subfamily (or Arbutoideae, depending on
the author), and Ericaceae family. In the Mediterranean region there are four species and two hybrids
in the genus Arbutus L.: Arbutus unedo L., A. andrachne L (eastern Mediterranean region), A. pavarii
Pampanini (coasts of Libya), A. canariensis Veill. (Canary Islands), A. x andrachnoides Link
(A. unedo x A. andrachne, in the eastern Mediterranean region), and A. x androsterilis Salas, Acebes &
OPEN ACCESS
Molecules 2014, 19 15800
Arco (A. unedo x A. canariensis, in the Canary Islands) [1]. Arbutus unedo L. is an evergreen shrub
that has a circum-Mediterranean distribution, being found in western, central and southern Europe,
north-eastern Africa (excluding Egypt and Libya) and the Canary Islands and western Asia, where
frost is not very usual and summer dryness is not very intense. In Europe, this species grows in
Portugal, Spain, France, Italy, Albania, Greece, Bosnia and Herzegovinia, Croatia, Macedonia,
Montenegro, Serbia and Slovenia and in the Mediterranean islands (Balearic, Corsica, Sardinia, Sicily
and Crete). It is also able to adapt to conditions of the south-western coast of Ireland [1–3].
The common English names are: arbutus, cane apples, Irish strawberry tree, Killarney strawberry
tree, strawberry madrone, and strawberry tree. The vernacular names in several southern European
countries are: ervedeiro, medronheiro (Portugal); albocera, alborocera, borrachín, madroñera, madroño
(Spain); arbousier, arbousier commun, fraisier en arbre (France); corbezzolo, sorbo peloso (Italy); and
koumaria (Greece) [3].
A. unedo grows to 9–12 m tall, but is normally between 1.5 m to 3 m tall [4]. The bark is fissured
and it peels off in small flakes, mostly dull brown. The leaves are alternate, simple, oblanceolate, dark
green, leathery and have a serrated margin, usually 2–3 times as long as wide, glabrous with a petiole
of 10 mm or less [5,6]. The flowers, with recurved lobes, are bell-shaped, 8–9 mm long, white, and
often pale pink [5]. A. unedo flowers are a significant source of nectar and pollen for bees [6]. The
fruits are globular, orange-red when ripe, growing up to 2 cm in diameter, are recovered with conical
papillae and mature in autumn [2,6]. Fruits take about 12 months to ripen; therefore, the tree carries
mature fruits and flowers at the same time. The flowering and fructification process extends from
October to February [7].
A. unedo prefers siliceous or decarbonated substrata and can grow on alkaline and relatively acidic
soils (pH 5–7.2) [1,4,6,8]. This species has a huge ecological importance since it prevents erosion of
the soils and has also the capacity to regenerate itself rapidly after fires, surviving quite well in poor
soils [7,9]. Strawberry trees are characterized by a wide genetic, morphological and phenological
variability [4,6,7,10–12]. Some studies have demonstrated that drought delays flowering and fruit
development in A. unedo. Summer drought and low minimum temperatures during the flowering phase
reduce fruit yields [13,14].
An ethnobotanical study, describing the wild edible plants in Biscay (Spain), found that strawberry
tree fruits had a significant cultural importance in that region, along with other nineteen wild edible
plants [15]. Nevertheless, fruits of A. unedo are rarely eaten as fresh fruit as despite their pleasing
appearance, the taste is not much appreciated by the consumer. So far, they are generally used for
obtaining alcoholic drinks (wines, liqueurs and brandies), jams, jellies and marmalades. They can also
be incorporated into yoghurts either in pieces or as flavours and be used, like other berries in
confectionery such as pie and pastry fillings, cereal products, among other applications [16–18].
In traditional folk medicine, A. unedo has been used in antiseptics, diuretics and laxatives and to
treat arterial hypertension. The leaves have been reported as possessing several biological properties
such as astringent, human platelet anti-aggregant due to its relative high amounts of tannins, urinary
antiseptic, anti-inflammatory, anti-diarrheal, anti-hypertension and anti-diabetic [19–32]. The present
work is focused in the chemical composition of different parts of the A. unedo shrub and its derived
products (honey and spirit beverages) as well as their biological properties.
Molecules 2014, 19 15801
2. Chemical Composition of A. unedo
2.1. Fruits
2.1.1. Phenols
Several components belonging to diverse phenol groups have been reported in Arbutus fruits: phenolic
acids, flavonols, flavan-3-ols and galloyl derivatives, and anthocyanins [16,21,22,26,27,33–35]. Gallic
acid (10.7 mg/g, dry weight) was the main phenolic compound reported by [16] in A. unedo fruits
collected in Samsun (Turkey), followed by protocatechuic acid, gentisic acid, p-hydroxybenzoic acid,
vanillic acid and m-anisic acid (Figure 1).
Figure 1. Some simple phenolics found in A. unedo fruits collected in Samsun (Turkey).
COOH
OH
OH
OH
COOH
OH
OH
COOH
OH
OH
COOH
OH
COOH
OCH3
OH
COOH
OCH3
Gallic acid Protocatechuic acid Gentisic acid
p-Hydroxybenzoic acid Vanillic acid m-Anisic acid
After separation by HPLC and on the basis of spectral identification, phenolics of full ripeness
strawberry tree fruits from the Cáceres region (Spain) were divided into seven subclasses and quantified:
catechin and procyanidin (expressed as (+)-catechin equivalents; detection wavelength, 280 nm);
hydroxybenzoic acids (as gallic acid equivalents, 280 nm); ellagitannins (as ellagic acid equivalents,
280 nm); ellagic acid (as ellagic acid equivalents, 365 nm); hydroxycinnamic acids (as cholorogenic acid
equivalents, 320 nm), flavonols (as rutin equivalents, 365 nm); and anthocyanins (as cyanidin-3-glucoside
equivalents, 520 nm), expressed as mg/100 g (d.w.). The concentrations found by the authors were:
catechins (313.4); hydroxybenzoic acids (112.2); hydroxycinnamic acids (1.0); flavonols (3.6); ellagic
acid (6.9); anthocyanins (5.8); procyanidins (474.1) [33].
The main phenolic compounds in wild fruits from North-eastern Portugal were flavan-3-ols and
galloyl derivatives (60.93 mg/100 g), followed by anthocyanins (13.77 mg/100 g) and flavonols
(10.86 mg/100 g) [34]. Identification of phenolic compounds was done by means of liquid
chromatography (HPLC) coupled to a diode array detector (DAD) and mass spectrometry (MS) using the
electrospray ionization interface (ESI). Quercetin galloylhexoside derivatives, quercetin-3-O-rutinoside,
quercetin-3-O-glucoside, quercetin pentoside, quercetin rhamnoside, kaempferol hexoside, and
myricetin rhamnoside constitute the flavonols found by the authors in Arbutus fruits. Within the group
of flavan-3-ols (36.30 mg/100 g) and galloyl derivatives (24.63 mg/100 g), the fruits had B1 dimer,
B-type proanthocyanidin trimers, B-type procyanidin tetramer, B-type procyanidin dimer, galloylquinic
acid, galloylhexoside acid, galloylshiquimic acid, (+)-catechin, digalloylquinic acid, digalloylquinic
shikimic acid and strictinin ellagitannin. Delphinidin-3-O-glucoside, cyanidin-3-O-glucoside and
cyanidin-3-O-pentoside were the anthocyanins identified and quantified by the authors in Arbutus
Molecules 2014, 19 15802
fruits from Northeastern Portugal [34]. Previously, [27] had already identified by HPLC-DAD/ESI-MS,
several phenolic compounds in fruits of A. unedo collected in the Natural Park of Montesinho
(Bragança, Northeast of Portugal): gallic acid glucoside, galloylquinic acid, quinic acid derivative,
proanthocyanidin dimer, galloylshikimic acid, digalloylquinic acid, digalloylshikimic acid, catechin
monomer, proanthocyanidin trimer, strictinin ellagitannin, ellagitannin derivative, galloyl derivative,
trigalloylshikimic acid, myricetin rhamnoside, quercetin glucoside, gallotannin, ellagic acid
rhamnoside (Figure 2). Practically the same phenolics and their derivatives were also identified in the
extracts of arbutus fruits collected in Arrábida Natural Park (Southern region of Portugal) [26].
Figure 2. Some chemical structures of galloyl derivatives, tannins and flavonols present in
A. unedo fruits.
OH COOH
O
O
O
O
OH
OH
OH
O
OH
OH
OH
O
OH
OH
OH
O
O
O
O
OH
OH
OH
O
OH
OH
OH
O
OH
OH
OH
COOH
Trigalloylquinic acid Trigalloylshikimic acid
OH
OH
OH
OH
OH
OH
O
O
O
O
OH
OH
O
O
OH
OH
OH
O
Strictinin (elagitannin) Ellagic acid rhamnoside
O
O
OH
OH
O
OH
O
O
O
OH
OH
OH
OOH
OH
OH
OH
O
OO
OH
OH
OH
CH2OH
OOH
OH
OH
OH
O
O
OH
O
OH
OH
OH
Quercetin-3-O-gluc oside Myricetin-3-O-rhamnoside
OOH
OH
OH
OH
O
O
O
OH
OH
OH
Quercetin-3-O-rhamnoside
The phenolic composition of fruits of strawberry tree from Salamanca, western Spain, was
evaluated in [22]. Some anthocyanins found by these authors in fruits were different from those found
Molecules 2014, 19 15803
in Portugal. Spanish fruits of strawberry fruits had delphinidin-3-galactoside, cyanidin-galactoside,
cyanidin-glucoside, and cyanidin-arabinoside. Among these anthocyanins, cyanidin-galactoside
prevailed (2.8 mg/100 g edible portion). The main anthocyanin in fruits from Portugal was
cyanidin-3-O-glucoside (11.40 µg/100 g, dry weight). Beyond the qualitative differences between
fruits from Portugal and Spain, quantitative differences can also be detected. Such differences may be
attributed to the different ways of quantification, among other reasons not discussed in the present
work. In Portuguese fruits, the authors [34] used an external standard for every anthocyanin, whereas
in Spanish fruits, the authors [22] used only one calibration curve obtained with cyanidin-3-glucoside.
In the flavonol group there were also some differences between fruits from Portugal and Spain. In
this country, the authors [22] reported myricetin-3-O-xyloside, quercetin-3-O-xyloside (both not
reported in Portuguese fruits), quercetin-3-O-rutinoside and quercetin-3-O-rhamnoside. Within the
group of flavan-3-ols and galloyl derivatives, [22] reported as being present in fruits of strawberry tree,
gallocatechin, gallocatechin-4,8-catechin, the proanthocyanidins B1 (epicatechin-4,8-catechin and
epicatechin-4,6-catechin), B2 (epicatechin-4,8-epicatechin), B3 (epicatechin-4,8-catechin), and B7
(epicatechin-4,6-catechin) dimers, epicatechin, epicatechin-4,8-epicatechin-4,8-catechin (Figure 3) and
epicatechin-4,8- epicatechin-4,8-epicatechin.
Figure 3. Chemical structures of the most abundant proanthocyanidins present in A. unedo fruits.
OOH
OH
OH
OH
OH
OH
OH
OH
OH
R1
R2
Proanthocyanidin B1: R1=OH; R2=H Proanthocyanifin B3 Proanthocyanidin B7
Proanthocyanidin B2: R1=H; R2=OH
OOH
OH
OH
OH
OH
OH
OH
OH
OH
OH
H
OOH
OH
OH
OH
OH
OH
O
OH
OH
OH
H
OOH
OH
OH
OH
OH
OH
O
OH
OH
OH
OH
OH
OH
OH
OH
OH
OOH
OH
OH
OH
OH
Catechin
OOH
OH
OH
OH
OH
OH
Gallocatechi n
Epicatechi n-4,8-epicatechin-4,8-c atechin (trim er)
Extracts of strawberry tree fruits, after enzymatic hydrolysis with hesperidinase followed by
cellulose, had gallic acid, protocatechuic acid, (+)-catechin, phloroglucinaldehyde, ellagic acid,
myricetin and quercetin [35]. The conjugated sugars found by these authors in the extracts were
glucoside, galactoside, rutinoside, rhamnoside and arabinoside.
The phenolic constituents of A. unedo fruits collected in Marina di Vecchiano, Pisa, Italy, included
anthocyanins (delphinidin-3-O-galactoside, cyanidin-3-O-glucose and cyanidin-3-O-arabinoside);
Molecules 2014, 19 15804
4-arbutin, β-D-glucogalline; 3-O-galloylquinic acid; gallic acid-4-O-β-D-glucopyranoside;
5-O-galloylquinic acid; 5-O-galloylshikimic acid; and 3-O-galloylshikimic acid (Figure 4), identified
by HPLC-DAD-ESI-MS, 1H- and 13C-NMR [21].
Figure 4. Chemical structures of some phenolic compounds, including anthocyanins, of
A. unedo fruits collected in Italy.
O+
OH
OH
OR2
OH
OH
R1
R
1
R
2
Anthocyanin name
OH galactose delphinidin-3-O-galactoside
H glucose cyanidin-3-O-glucoside
H arabinose c
y
anidin-3-O-arabinoside
OH
OH
OH
O
O
COOH
OH
OH
OH
OH
OH
O
O
OH COOH
OH
OH
OHGluO
OH
OH
OH
O
OH COOH
OH
OH
OH
OH
OH
GluO
O
OH
OH
OH
O
O
COOH
OH
OH
OH
OH
COOH
O
GluO
Arbutin -D-Glucogalline Gallic acid-4-O- -D-glucopiranoside
β
β
3-O-Galloylquinic acid 5-O-Galloylquinic acid
5-O-Galloylshiquimic acid 3-O-Galloylshiquimic acid
2.1.2. Fatty Acids
α-Linolenic (36.51%), linoleic (21.50%) and oleic acids (21.01%) were the predominant
unsaturated fatty acids, and palmitic acid the most important saturated fatty acid (8.20%) found by [36]
in ripe fruits of strawberry tree fruits collected in the Natural Park of Montesinho territory
(Trás-os-Montes, north-eastern Portugal). Fatty acids composition checked in fruits at different
ripening stages and collected in Trás-os-Montes (North-eastern Portugal) showed that their profiles
were very similar between the unripe and ripe stages, being α-linolenic (36.9%–43.04%, respectively),
linoleic (20.14%–18.84%, respectively) and oleic acids (29.38%–26.75%, respectively), the three
major ones. α-Linolenic (31.26%), linoleic (24.26%) and oleic acids (24.82%) were also predominant
in fruits collected in central and western Spain [37]. Polyunsaturated fatty acids (PUFA) were the
major fraction of fatty acids either in Portuguese or Spanish fruits, represent at least 52% of the total
fatty acids. These fruits had a highly favourable ω3/ω6 ratio, due to the richness in α-linolenic [29], as
well as a good PUFA/SFA (saturated fatty acids) (2.85), considered as cardioprotective [36,37].
Strawberry tree fruits from Croatia also had as main fatty acids linoleic and linolenic acids (34.8%
and 31.3%, respectively), but the third more important was palmitic acid (19.0%) and not oleic acid
(14.9%) [38] as reported above for the other samples from different locations.
Molecules 2014, 19 15805
2.1.3. Vitamins and Others
Fruits of strawberry tree from Trás-os-Montes (North-eastern Portugal) contained vitamin E.
Among the vitamin E vitamers, the most important was γ-tocotrienol. The total free vitamin E content
reduced with ripening: from 1369 mg/kg in unripe fruits to 557 mg/kg in ripe ones [29]. α-, β-, γ- and
δ-Tocopherols and α-tocotrienol were also present in fruits (Figure 5). Other studies characterizing the
nutrients and phytochemicals with antioxidant properties of strawberry tree fruits collected in the
Natural Park of Montesinho territory, in Trás-os-Montes, North-eastern Portugal, also showed the
presence of tocopherols (235 mg/kg), being α-tocopherol the most important (235 mg/kg), followed by
γ- tocopherol and β-tocopherol [36]. These authors did not find δ-tocopherol in fruits.
Figure 5. Chemical structure of vitamin E and some carotenoids of A. unedo fruits.
O
OH
O
OH
O
OH
O
OH
α
-Tocop herol - Tocopher ol
γ
-Tocop herol - Tocopher ol
δ
O
OH
O
OH
H
O
OH
O
OH
α
γ
δ
-Tocotrienol -Tocotrienol
-Tocotrienol - T ocotrienol
OH
OH
H
Lutein
Lycopene
-Carot ene
The presence of α-tocopherol was also reported by [22], nevertheless in much lower amounts
(0.2 mg/kg) than those reported by other authors [29,36] (271 mg/kg in unripe fruits to 32 mg/kg in
ripe fruits). Total vitamin E in wild fruits of strawberry fruits from Central and Western Spain was also
evaluated by [37]. The concentration (39 mg/kg) found by these authors were similar to those reported
by [29] in ripe fruits. Among the vitamin E isomers, the authors found that α-tocopherol predominated
(35 mg/kg), followed by γ- tocopherol, β-tocopherol and δ-tocopherol.
Molecules 2014, 19 15806
Vitamin C has also been reported as being present in arbutus fruits but found in distinct
concentrations: 89 mg/100 g [35]; from 542 mg/100, in unripe fruits, to 346 mg/100 g, in red mature
fruits [17]; 6 mg/100 g [22]; 119.1 mg/100 g [39]; and 182 mg/100 g [37]. Studies performed by [31]
demonstrated the importance of harvest date and location on the amounts of total vitamin C
(262.7–122.0 mg/100 g, f.w.); ascorbic acid (203.8–93.1 mg/100 g); dehydroascorbic acid
(90.8 mg/100 g—not detected); β-carotene (0.808–0.243 mg/100 g); and lycopene (0.209 mg/100 g—
not detected).
β-Carotene, niacin, lutein+zeaxanthine, and β-cryptoxanthyne were also reported as constituents of
Spanish and Portuguese fruits of strawberry tree [17,22]. Ripe fruits collected in Croatia contained
271 mg/100 g (f.w.) vitamin C, of which 255.3 mg/100 g was ascorbic acid and 16.2 mg/100 g was
dehydroascorbic acid [38]. In North-western Turkey, wild strawberry tree fruits had ascorbic acid
(270.50 mg/100 g) [40], which concentration is within the range found for other samples with different
origins [31,38].
Triterpenes were also found in fruits of A. unedo when separated and identified by high pressure
liquid chromatography coupled to a mass spectrometer by means of a particle beam interface
(HPLC-PBMS). Through this methodology, the authors identified α- and β-amyrin, lupeol as well as a
new natural triterpene (olean-12-en-3β,23-diol) (Figure 6) [41].
Figure 6. Chemical structure of some triterpenes found in fruits and other parts of A. unedo.
OH CH2OH OH
OH
H
OH
H
α
β
-Amyrin -Amyrin
Olean-12-en-3 ,23-diol Lupeol
β
OOH AcO
COOH
OH
COOH
OH
COOH
O
OH
7 -hydroxystigmast-4-en-3-one Pomolic acid 3-acetate
β
Betulinic acid Platanic acid
β
-Sitosterol
Molecules 2014, 19 15807
2.1.4. Organic Acids
Fumaric (1.49 mg/g, d.w.), lactic (0.49 mg/g), malic (0.84 mg/g), suberic (0.23 mg/g) and citric
(0.01 mg/g) acids were the organic acids detected and quantified by [16] in A. unedo fruits from
Samsun, Turkey. In Spain, fruits of strawberry tree had only oxalic acid (96.53 mg/100 g, f.w.); and
fumaric acid (0.73 mg/100 g), according to the results reported by [37]. Some variability in the organic
acids content of strawberry tree fruits was found in samples gathered in three different seasons
(November and December 2007–2009) and from two localities with different environmental conditions
(Madrid, center of Spain; and Cáceres, west of Spain): oxalic acid (146.75–48.44 mg/g, f.w.); malic
acid (314.94–203.3 mg/g); and fumaric acid (0.919–0.539 mg/g) [31]. In Portugal, fruits harvested in
Tapada da Ajuda, Lisboa, had malic and quinic acids (Figure 7), which concentrations depended on the
ripening stage of fruits [17]. In contrast to those samples from Turkey, in which fumaric acid
predominated, in Portugal only traces were detected mainly in red mature fruits.
Figure 7. Chemical structures of some organic acids found in A. unedo L.
OH
O
O
OH
OH
OOH
O
OH OH
O
OH
O
OH
OH
O
OH
OO
OH OH
O
OH
O
OH
O
OH
OH OH
OH OH
O
Oxalic acid Malic acid Fumaric acid Lactic acid
Citric acid Suberic acid Quinc acid
2.1.5. Sugars
Fructose (27.8%, d.w.) and glucose (21.5%, d.w.) were the predominant sugars in fruits from
Turkey, followed by sucrose (1.80%) and maltose (1.11%) [16]. Similar concentrations of fructose,
glucose and sucrose were also reported by Şeker and Toplu [40] in Arbutus fruits collected in
North-western Turkey (24.09, 19.09% and 2.65%, d.w., respectively). In the Natural Park of
Montesinho territory, in the Trás-os-Montes, North-eastern Portugal, the major sugar was also fructose
(24.21%, d.w.) in fruits of strawberry tree, but the glucose amount was much lower (12.14%) and sucrose
level was much higher (4.20%) than those reported by [16,40] for Turkish fruits. Alarcão-e-Silva et al. [17]
found that the amounts of glucose and fructose were dependent on the ripening stage, whereas sucrose
content did not change (8.77 and 8.68%, d.w.) in unripe and red mature fruits, respectively. Glucose
amount ranged from 3.95 in unripe fruits to 12.5% in red mature fruits (d.w.). This difference between
two ripening stages was even higher for fructose (2.33–20.8, d.w., respectively). A great variability in
fructose (12.69%–3.65%, f.w.) and glucose (6.50%–2.34%) amounts were reported by [31] in fruits of
A. unedo, depending on the harvest date and location of the orchards (center and west of Spain). For
the same samples, the levels of sucrose ranged from 0.48% to absence. The levels of fructose and
glucose in strawberry tree fruits collected in Croatia were within the range reported for Portuguese and
Spanish samples (12.62% and 5.27%, respectively) [38].
Molecules 2014, 19 15808
2.1.6. Volatiles
The analysis of the volatiles of strawberry tree fruits performed using headspace-solid phase
micro-extraction (HS-SPME) allowed the identification of a total of 41 compounds in Portuguese
samples. The fruits were collected at different ripening stages in the region of Trás-os-Montes
(north-eastern Portugal). Alcohols [(Z)-3-hexen-1-ol, 1-hexanol] are the main volatile compounds
detected in the three ripening stages, followed by aldehydes [hexanal, (E)-2-hexenal], and esters
[(Z)-3-hexenyl acetate] [42]. Generally, these volatiles decreased during ripening, maybe due to the
reduction of the activity of lipoxygenase [42]. The remaining chemical classes found in fruits were
norisoprenoid derivatives, sesquiterpenes and monoterpenes but in very low amounts. In the progress
of the fruit ripening, the amounts of monoterpenes decrease from unripe to intermediate maturation,
presenting in the ripe stage the highest quantity; whereas sesquiterpenes increase their amount from
unripe to intermediate fruits, after which their presence was lower. Norisoprenoids derivatives
decrease their presence as the maturation increases [42].
The essential oil isolated from fruits of A. unedo in the north-eastern Turkey by hydrodistillation
and analysed by GC-MS was mainly constituted by hexadecanoic acid, ethyl dodecanoate, ethyl
linoleate, tetradecanoic acid, and trans-carane [43]. Flower oil had a different chemical profile because
the major components were hexadecanoic acid, α-terpineol, nonanal and linalool [43].
2.1.7. Minerals
The mineral composition of arbutus fruits reported for Turkish samples collected in Mersin (Turkey)
was: Ca (4959 mg/kg) , K (14,909 mg/kg), Mg (1316 mg/kg) , Na (701 mg/kg) and P (3669 mg/kg) as
main minerals, whereas Cd, Cu, Li Mn, Ni, Pb and Sr contents were very low [44]. In other work,
fruits collected in the North-eastern Anatolia region of Turkey had K (119 mg/100 g); P (12.6 mg/100 g);
Ca (12 mg/100 g); Mg (9.1 mg/100 g); Fe (1.25 mg/100 g); Cu (0.088 mg/100 g); Zn (2.602 mg/100 g);
and Mn (0.197 mg/100 g) [39]. In the North-western regions of Turkey, K (11,346 mg/kg and
13,661.45 mg/kg); Ca (5673.39 mg/kg and 5475.62 mg/kg); P (4278.38 mg/kg and 4554.91 mg/kg);
Mg (1691.46 mg/kg and 1931.49 mg/kg); and Na (1136.79 mg/kg and 1034.53 mg/kg) were also the
main minerals found by [40,45]. Samples collected in Croatia had K (118.61 mg/100 g); Na
(20.63 mg/100 g); Ca (36.05 mg/100 g); Mg (9.66 mg/100 g); Fe (1.29 mg/100 g); P (19.99 mg/100 g);
Zn (0.45 mg/100 g); Mn (<0.99 mg/100 g); Cr (<0.99 mg/100 g); Ni (<0.10 mg/100 g); Pb
(<1.32 mg/100 g); and Cd (<0.10 mg/100 g) [38].
A wide variability in the mineral composition of strawberry tree fruits was found in samples
gathered in three different seasons (November and December 2007–2009) and from two localities with
different environmental conditions (Madrid, center of Spain; and Cáceres, west of Spain): Na
(9.94–4.33 mg/100 g, f.w.); K (323.14–79.72 mg/100 g); Ca (104.12–40.54 mg/100 g); Mg
(45.85–9.56 mg/100 g); Cu (0.208–0.073 mg/100 g); Fe (1.856–0.354 mg/100 g); Mn
(0.178–0.038 mg/100 g); and Zn (0.762–0.188 mg/100 g) [31]. According to the results of the authors,
the year of harvest significantly influenced the fruit content of K, Mg, Cu, Fe, Mn and Zn.
Molecules 2014, 19 15809
2.2. Leaves
Arbutin was reported as being present in leaf extracts of A. unedo collected in Montenegro, along
with hydroquinone derivatives [46]. Quercitrin, isoquercitrin, hyperoside, and chlorogenic acid are
other phenolic compounds identified and quantified by [5,47] in extracts of leaves of A. unedo from
Croatia. In this work, the authors also reported that the concentrations of these compounds changed
over the year. For example, higher concentrations of hyperoside and quecitrin were found in January,
whereas chlorogenic acid was in higher amounts in June, July and October.
Leaf extracts of A. unedo from the Natural Park of Montesinho (Bragança, Northeast of Portugal)
after LC-DAD-ESI/MS were shown to have flavanols (catechins, procyanidin dimers and respective
gallate esters), flavonols (glucosides of myricetin, quercetin, kampferol), several galloyl (gallotannins)
and ellagic (ellagitannins) derivatives. These compounds were also present in fruit extracts; however
the number of compounds identified was higher in leaf extracts than in fruit [27].
α-Tocopherol was also found in leaves of A. unedo from Turkey, being the amounts found dependent on
the collection season. Leaves collected in March had the highest concentration of α-tocopherol [48].
The essential oil of A. unedo leaves, collected in West Anatolia in Izmir-Cicekliköy (Turkey),
obtained by hydrodistillation had (E)-2-decenal, α-terpineol, hexadecanoic acid, and (E)-2-undecenal
as main components [49]. A distinct chemical composition was reported for essential oil of leaves
isolated from A. unedo of Algerian origin: palmitic acid, linoleic acid and 2,6-di-tert-butyl-p-cresol [50].
Volatile organic compounds emitted by the aerial parts of A. unedo, including leaves, were also studied
in fields of Italy and Spain. Nonanal, decanal, 2-ethoxyethyl acetate and monoterpene hydrocarbons
and oxygenated monoterpene were identified [51,52].
2.3. Stems
Catechin and epicatechin are monomers constituting the proanthocyanidin also known as condensed
tannins, a broad family of oligomers and polymers belonging to the flavonoid class. The stems of
A. unedo L. from Algeria after extraction using a water/methanol/acetone mixture and structural
analysis by 1H-NMR, 13C-NMR, IR and mass spectra using an ion-trap spectrometer, operating on an
ESI mode showed the presence of (+)-catechin, (+)-afzelechin and (3,4-dihydroxyphenyl)-5,7-
dihydroxychroman-3-yl 4-hydroxybenzoate [53].
2.4. Roots
The roots of Arbutus unedo L. from the Terni forest (Tlemcen, Algeria) extracted with a
water/methanol/acetone mixture had two major compounds identified by NMR spectroscopy:
(+)-catechin and (+) catechin gallate. Other phenolic compounds were also identified by GC-MS such
as benzoic acid, 4-(acetyloxy)-3-methoxy-, methyl ester; 4-hydroxyphenyl acetic acid; caffeic acid;
gallic acid; protocatechic acid and bis(2-ethylhexyl) phthalate [54].
2.5. Seeds
The triacylglycerol characterisation of A. unedo seeds made by [55] revealed low saturated fatty
acids, high content of oleic acid, a significant presence of ω6 and ω3 unsaturated fatty acids with a low
Molecules 2014, 19 15810
ω6/ω3 fatty acid ratio. The distribution of fatty acids among the three sn-positions of triacylglycerol is
asymmetric, nevertheless with a high incorporation of essential fatty acids in the sn-2-position, which
is very important from a nutritional point of view [55].
2.6. Entire Plant
From the hydro-alcoholic extract of the entire plant of A. unedo collected in a Mediterranean
woodland coppice, located in Central Italy, 12 phenolic compounds were identified: ethyl gallate,
arbutin and two arbutin derivatives (p-hydroxybenzoyl arbutin and galloyl arbutin) and eight
flavonoids (gallocatechin, catechin, kaempferol 3-O-α-L-rhamnoside, quercetin 3-O-α-L-rhamnoside,
myricetin 3-O-α-L-rhamnoside, kaempferol 3-O-β-D-arabinoside, quercetin 3-O-β-D-arabinoside, and
myricetin 3-O-β-D-arabinoside) [56].
Triterpenes were also found in the petroleum ether and ethyl acetate extracts of entire plant
collected in Turkey: α-amyrin acetate, betulin, betulinic acid, 6β-hydroxystigmast-4-en-3-one, lupeol,
platonic acid, pomolic acid 3-acetate, β-sitosterol and 7β-hydroxystigmast-4-en-3-one (Figure 6) [57].
3. Biological Properties and Applications
3.1. Fruits
The extracts of A. unedo fruits revealed to have in vitro antioxidant activity [26,29,36,37,40,58–62].
The type of extraction of phenols present in fruits of A. unedo influenced the antioxidant activity. The
capacity for scavenging free radicals of the ripe fruit extracts of strawberry tree obtained by
supercritical fluid extraction in the adequate values of pressure (60 bar), temperature (48 °C),
concentration of co-solvent (ethanol 19.7%) by CO2 flow rate of 15 g/min for 60 min, at a solvent/feed
ratio of 30 was better when compared to that obtained by solid-liquid extraction (Soxhlet) using
ethanol as extraction solvent, but similar when compared to the water extracts. In contrast, the capacity
for preventing lipid peroxidation, measured through the β-carotene bleaching method, was better in
water extract [58]. According to these authors this extract had the lowest oxidation rate (0.661) and the
highest activity coefficient (809) in comparison to supercritical CO2 (0.958 and 492, respectively) and
ethanol extracts (1.101 and 330, respectively).
The antioxidant capacity of fruit extracts reported by [59] was higher when obtained from fully red
fruits, except H2O2 scavenging activity which was higher in green fruit. The concentrations of red and
yellow fruit extracts providing 50% antioxidant activity (EC50) were 0.409 and 0.499 mg/mL,
respectively, in the DPPH (2,2-diphenyl-1-picrylhydrazyl) method. The EC50 values found when
the β-carotene bleaching method was used were 0.246 and 0.328 mg/mL in red and yellow fruit
extracts, respectively. The H2O2 scavenging capacity was low (27.10% and 25.86% for green and red
fruit extracts, respectively). The influence of maturation stage on antioxidant activity measured
through the DPPH method was also found by [29]. Intermediate (EC50 = 0.37 mg/mL) and ripe fruits
(EC50 = 0.25 mg/mL) of strawberry tree fruits possessed higher antioxidant activity than unripe fruits
(EC50 = 0.58 mg/mL). Storage of fresh fruits of A. unedo at 0 °C preserved better the antioxidant
activity than at higher temperatures (3 and 6 °C) during the experimental period (15 days) [61], evaluated
by the capacity for scavenging peroxyl radicals [Oxygen Radical Absorbance Capacity—ORAC
Molecules 2014, 19 15811
method] and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) cation radicals [Trolox
Equivalent Antioxidant Capacity-TEAC method]. In the same experiment, the authors also reported
that the type of films covering the fruits (linear low density polyethylene or polyethylene film
perforated with holes) did not influence the antioxidant activity of fresh fruits [61].
The antioxidant activity was influenced by the drying fruit processes. Some authors [60] reported
that fruits submitted to freeze drying had higher capacity for scavenging DPPH free radicals
(EC50 = 2.125 mg/mL) and preventing lipid peroxidation (EC50 = 0.290 mg/mL) than those submitted
to hot air drying (EC50 = 6.956 and 0.880 mg/mL, respectively). This loss when using hot air drying
would be expectable due to the possible degradation and/or loss of some compounds such as phenols
and vitamins [60,63].
Beyond the antioxidant activity of fruit extract of A. unedo found by [62] measured through the
capacity of the extract with phenolic acids, flavones/ols, flavan-3-ols and galloyl derivatives to inhibit
peroxidation in animal brain homogenates, the same extract had also antitumor potential against
NCI-H460 human cell line (non-small lung cancer). The authors obtained two main types of extracts
from Arbutus unedo, Prunus spinosa, Rosa micrantha and Rosa canina fruits collected in Portugal:
non-anthocyanin phenolic compounds enriched extract and anthocyanins enriched extract.
Non-anthocyanin phenolic compounds enriched extract of A. unedo had the highest capacity to inhibit
lipid peroxidation in animal brain homogenates (EC50 = 7.21 μg/mL) as well as a high antitumor
potential against NCI-H460 human cell line. The authors considered that such activities might be
attributed to the presence of galloyl derivatives exclusively found in this species [62].
The antioxidant ability of strawberry tree fruits has led to the application of their phenolic-rich
extracts as functional ingredients in processed meat products [33,64–66]. For example, the
combination of fruits extracts together with sodium ascorbate and sodium nitrite enhance the oxidative
stability of frankfurters without modifying their colour and texture properties. The utilization of fruit
extracts also minimized the deterioration of quality during the refrigerated storage [64]. The addition
of extracts from A. unedo fruits in porcine burger patties protected polyunsaturated fatty acids from
oxidative degradation, inhibited the formation of thiobarbituric acid reactive substances and volatiles
compounds; and the oxidation of proteins preventing the formation of carbonyl compounds [33,65,66].
The utilization of these extracts as antioxidants enhanced the nutritional, safety and sensory properties
of porcine burger patties [33,65,66].
Other applications of fruit extracts in food technology have been reported, such as the enrichment
of yogurts with fruit extract of A. unedo which improved the antioxidant activity and the survival of its
microbial community, not affecting the chemical and microbiological characteristics of yogurts [67].
Fruit essential oil of A. unedo showed a moderate antibacterial activity against Listeria monocitogenes
and Enterococcus faecalis [43].
3.2. Leaves
Antioxidant activity in chemical based model assays has been reported for leaf extracts of
A. unedo [20,28,30,32,68,69], and cell based model assays [27]; antibacterial activity, mainly against
Gram-positive bacteria [68–70], Helicobacter pylori and Klebsiella pneumoniae [71]; antifungal effect
against two aflatoxigenic molds namely Aspergillus parasiticus NRRL 2999 and NRRL 465 [68] and
Molecules 2014, 19 15812
against Candida tropicalis [71]; intracellular anti-mycobacterial activity without toxic effect on
macrophages, especially ethanolic extract [70] (Table 1); in vitro anti-leishmanial activity, mainly
ethanolic extracts [72]; in vitro activity against Trichomonas vaginalis trophozoites, mainly an ethyl
acetate extract [73]; anti-inflammatory activity of aqueous extracts by down-regulating Signal
Transducer and Activator of Transcription 3 (STAT3) activation induced by injection of carrageenan
in the pleural cavity of mice [74], or by down-regulation of STAT1 elicited by IFN-γ (interferon-γ),
both in human breast cancer cell line MDA-MB-231 and in human fibroblasts [75].
Table 1. Antimicrobial activities reported for leaf extracts of A. unedo.
Microorganism Extract Activity Ref.
Gram Positive
Staphylococcus aureus Aqueous
Inhibition
zone
diameter
10.5 mm (10 μL/disc)
[68] 13.8 mm (20 μL/disc)
21.1 mm (40 μL/disc)
Bacillus cereus
Aqueous
Minimum
inhibitory
concentration
(MIC)
1 mg/mL
[69]
B. subtilis 1 mg/mL
Staphylococcus epidermis 1 mg/mL
S. aureus 2.5 mg/mL
B. cereus ATCC 11771
Acetone/water (60:40)
Inhibition
zone
diameter
10.0 mm (2 mg/disc)
[71]
Ethanol 95% 11.3 mm
Methanol (Soxhlet) 10.0 mm
Methanol (maceration) 10.7 mm
Ethanol (maceration) 9.3 mm
S. aureus ATCC 25923
Acetone/water (60:40)
Inhibition
zone
diameter
9.3 mm
[71]
Ethanol 95% 12.0 mm
Methanol (Soxhlet) 10.3 mm
Methanol (maceration) 9.3 mm
Ethanol (maceration) 9.3 mm
Enterococcus faecalis
ATCC 29212
Acetone/water (60:40)
Inhibition
zone
diameter
8.0 mm
[71]
Ethanol 95% 6.5 mm
Methanol (Soxhlet) 7.0 mm
Methanol (maceration) 7.3 mm
Ethanol (maceration) 7.3 mm
Clinical Methicillin-
Resistant Staphylococcus
aureus 10/8
Acetone/water (60:40)
Inhibition
zone
diameter
7.8 mm
[71]
Ethanol 95% 8.8 mm
Methanol (Soxhlet) --
Methanol (maceration) 8.0 mm
Ethanol (maceration) 8.0 mm
Clinical Methicillin-
Resistant Staphylococcus
aureus 12/8
Acetone/water (60:40)
Inhibition
zone
diameter
7.0 mm
[71]
Ethanol 95% 9.5 mm
Methanol (Soxhlet) --
Methanol (maceration) --
Ethanol (maceration) --
Mycobacterium smegmatis
Aqueous MIC
6.02 mg/mL
[70]
M. aurum A+ 5.59 mg/mL
M. bovis PPI 6.02 mg/mL
Molecules 2014, 19 15813
Table 1. Cont.
Microorganism Extract Activity Ref.
Gram negative
Pseudomonas aeruginosa Aqueous MIC
5 mg/mL [69]
Escherichia coli 5 mg/mL
Klebsiella pneumoniae
ATCC 13833
Acetone/water (60:40)
Inhibition
zone
diameter
9.0 mm (2 mg/disc)
[71]
Ethanol 95% 10.8 mm
Methanol (Soxhlet) 9.8 mm
Methanol (maceration) 9.3 mm
Ethanol (maceration) 8.7 mm
Helicobacter pylori 104/98
Acetone/water (60:40)
Inhibition
zone
diameter
18.3 mm
[71]
Ethanol 95% 14.6 mm
Methanol (Soxhlet) 17.7 mm
Methanol (maceration) 16.7 mm
Ethanol (maceration) 13.5 mm
Helicobacter pylori P10/92
Acetone/water (60:40)
Inhibition
zone
diameter
17.8 mm
[71]
Ethanol 95% 14.6 mm
Methanol (Soxhlet) 15.5 mm
Methanol (maceration) 14.6 mm
Ethanol (maceration) 14.9 mm
Helicobacter pylori 93/00
Acetone/water (60:40)
Inhibition
zone
diameter
12.9 mm
[71]
Ethanol 95% 11.1 mm
Methanol (Soxhlet) 12.3 mm
Methanol (maceration) 11.8 mm
Ethanol (maceration) 11.5 mm
Helicobacter pylori B22/96
Acetone/water (60:40)
Inhibition
zone
diameter
18.0 mm
[71]
Ethanol 95% 17.5 mm
Methanol (Soxhlet) 18.2 mm
Methanol (maceration) 18.3 mm
Ethanol (maceration) 15.8 mm
Helicobacter pylori ATCC
710392
Acetone/water (60:40)
Inhibition
zone
diameter
10.4 mm
[71]
Ethanol 95% 7.6 mm
Methanol (Soxhlet) 9.1 mm
Methanol (maceration) 9.0 mm
Ethanol (maceration) 8.1 mm
Fungi
Aspergillus parasiticus
NRRL 2999 (0.075%–0.3%) Aqueous Inhibitory
effect
30.15%–42.70%
[68]
Aspergillus parasiticus
NRRL 465 (0.075%–0.3%) 12.79%–29.76%
Yeasts
Candida tropicalis ATCC
750
Acetone/water (60:40)
Inhibition
zone
diameter
9.3 mm (2 mg/disc)
[71]
Ethanol 95% 13.3 mm
Methanol (Soxhlet) 10.7 mm
Methanol (maceration) 12.0 mm
Ethanol (maceration) 12.7 mm
Molecules 2014, 19 15814
The antioxidant activity was dependent on the solvent extraction [20,28,68]. The Trolox equivalent
antioxidant capacity of ethanol and methanol extracts of A. unedo leaves were 2.25 mM and
1.75 mM, respectively [20]. Ethanol extracts of A. unedo leaves were the highest in reducing power
(IC50 = 232.7 μg/mL) and DPPH scavenging effect (IC50 = 63.2 μg/mL), followed by water extracts
(IC50 = 287.7 and 73.7 μg/mL, respectively). Methanol extracts were the best for scavenging
superoxide anion radicals (IC50 = 6.9 μg/mL) [28]. The capacity for scavenging DPPH free radicals
found by other authors [68] was better in methanol leaf extracts [EC50 = 0.4232 mg/mL) than in
ethanol (EC50 = 0.4872 mg/mL) or aqueous extracts (EC50 = 0.6554 mg/mL) in contrast to those
reported by [28]. For the same concentration of samples and standard (BHT) assayed (50 μg/mL), the
β-carotene bleaching activity of methanol extracts (55.20%) was also higher than the remaining
samples but significantly lower than BHT (91.1%) [68]. The capacity for scavenging H2O2 was similar
for both aqueous (26.02%) and methanol (28.22%) extracts but significantly lower than BHT (85.75%)
when the concentration assayed in all cases was 250 μg/mL [68]. Metal chelating activity was also higher
in those extracts (14.05%–14.46%) but much lower when compared to the EDTA (67.90%) [68].
The collection zone and genotype also influenced the antioxidant properties of A. unedo extracts of
leaves [30,69]. Samples collected in Greece showed significantly higher spasmolytic activity
(IC50 = 1.66 mg/mL) and DPPH free radical scavenging capacity (IC50 = 4.77 μg/mL) than the samples
collected in Montenegro (IC50 = 5.26 mg/mL and 7.14 μg/mL, respectively). The inhibition of lipid
peroxidation in liposomes induced by Fe2+/ascorbate and determined through thiobarbituric test
activity was also higher in sample extracts from Greece, particularly when phenol content was
lower [30]. The reducing power and the capacity of scavenging DPPH free radicals were evaluated in
19 genotypes of A. unedo collected in the Trás-os-Montes region of Portugal [69]. In reducing power
and DPPH methods, the strongest (EC50 = 0.234 mg/mL and 0.089 mg/mL, respectively) and the
weakest activities (EC50 = 0.378 mg/mL and 0.142 mg/mL, respectively) were found in samples
collected in Vila Verde and Vila Boa 2, respectively [69].
Boulanouar et al. [32], studying the antioxidant activity of eight Algerian leaf extracts, measured
through several in vitro methods, showed that A. unedo extract was the most active for scavenging
ABTS (IC50 = 0.009 mg/mL), DPPH (IC50 = 0.006 mg/mL) and superoxide anion radicals
(IC50 = 0.084 mg/mL).
The human erythrocyte as a cell-based model system was used to elucidate the antioxidant activity
of A. unedo extracts [27]. In such model, the peroxidative injury in human erythrocytes is induced by
AAPH [2,2'-azobis(2-amidinopropane) dihydrochloride]. The results obtained by the authors showed
that leaf extracts were better to prevent peroxidation than fruit extracts. The IC50 values found for leaf
and fruit extracts were 0.062 and 0.430 mg of extract/mL, respectively, after 3 h of incubation, but
significantly lower than that obtained with ascorbic acid, used as standard (0.031 mg/mL).
According to some authors [23], leaf extracts of A. unedo may be used for the treatment and/or
prevention of cardiovascular diseases because their studies demonstrated that such samples reduced
store-operated Ca2+ entry induced by thrombin or by selective depletion of the two Ca2+ stores in
platelets, the dense tubular system and the acidic stores. The same extracts were also able to reduce
both basal and thrombin-stimulated protein tyrosine phosphorylation. Therefore, the extracts have
in vitro anti-aggregant effects in human platelets. An anti-aggregant effect was also reported by [76]
Molecules 2014, 19 15815
but in rat platelets. The authors reported that tannins isolated from the methanol extract presented a
strong anti-platelet effect and therefore responsible for such action.
Ethanol extracts of A. unedo leaves collected in Greece and Montenegro possessed spasmolytic
activities in rat ileum, probably mediated via the inhibition of Ca channels. The authors attributed this
action to the relative high contents of phenols, tannins, arbutin and flavonoids [30]. Extracts rich in
oligomeric condensed tannins and catechin gallates possessed an endothelium-dependent, vasorelaxant
activity. Pre-contracted aortic rings, previously removed from male Wistar rats, with noradrenaline,
relaxed strongly in the presence of A. unedo extracts [77].
3.3. Roots
The aqueous extract of roots had antibacterial activity on Escherichia coli comparable to that of
piperacilline (diamter of inhibition zone = 30 mm in both cases) [54]. Moderate antibacterial activity
was reported by [78] for water extract and phenolic fractions of A. unedo collected in Tlemcen
(Algeria) against E. coli (MIC = 200 μg/mL) and Staphylococcus aureus (MIC = 200 μg/mL for a
fraction obtained by column chromatography after elution with 50% methanol/water (v/v) containing
0.1% (v/v) acetic acid. Such activity could be attributed to the secondary metabolites detected in
samples such as quinones, anthraquinones, flavonoids, tannins and anthocyanins [78].
The biological properties of root extracts from diverse locations are largely referred. Hypoglycemiant
effect of aqueous extracts of A. unedo from Morocco in neonatal streptozotocin-induced diabetic rats
under chronic treatment [79]. Chronic treatment with aqueous extracts of A. unedo roots reduced
hypertension development; prevented the myocardial hypertrophy; ameliorated vascular reactivity and
renal functional parameters caused by L-NG-Nitroarginine methyl ester (L-NAME) of male Wistar
rats [80]. The extracts also improved the sensitivity of the arterial baroreceptor controlling the heart
rate to acute increases of arterial pressure [80].
3.4. Entire Plant
Anti-inflammatory activity of entire plant extracts of strawberry tree was also reported by
Carcache-Blanco et al. [57], through the inhibition of cyclooxygenase-2 (COX-2). This property was
more evident for some compounds isolated from extracts: 7β-hydroxystigmast-4-en-3-one, ()-catechin,
lupeol, betulinic acid, and α-amyrin acetate.
4. Other Products Obtained from A. unedo
4.1. Honey
Strawberry tree honey is a known product of Mediterranean regions which is characterized for its
“bitter taste” [81]. Homogentisic acid (2,5-dihydroxyphenylacetic) has been considered as a chemical
marker of the botanical origin of strawberry tree honey [82,83] along with (±)-2-cis,4-trans-abscisic
acid (c,t-ABA), (±)-2-trans, 4-trans-abscisic acid (t,t-ABA) and unedone [84]. From the aromatic
profile of strawberry tree honey from Sardinia (Italy) and Canary islands (Spain) some authors [85,86]
reported that norisoprenoids such as α-isophorone, β-isophorone and 4-oxoisophorone (Figure 8) could
be considered specific floral origin markers. Proline was found to be the main free amino acid,
Molecules 2014, 19 15816
followed by glutamic acid, arginine, alanine and phenylalanine in strawberry tree honey [87]. The
antioxidant and anti-radical activities [88–91] of strawberry tree honey have been attributed to the
homogentisic acid [91].
Figure 8. Chemical structures of markers of the botanical origin of strawberry tree honey.
OH
OH
O
OH OOHO
OH
O
OH
OH
O
O
OH
OH
O
O
OO
O
Homogentisic acid 2-cis,4-trans-Abscisic acid 2-trans,4-trans-Abscisic acid
Unedone -Isophorone - Isophorone 4-Oxoisophorone
α
β
4.2. Spirit Beverages
The spirit beverage that comes from the distillation of fermented fruits of A. unedo has also been target
of chemical surveys. In Portugal, this distilled beverage is known as “aguardente de medronho” [92]; in
Italy as “Corbezzolo” [93], and in Greece as “Koumaro” [18]. In Portugal, two denominations of
origin distillates are already recognized: Medronho do Algarve e Medronho do Buçaco [94].
In Portugal, “aguardente de medronho” has as main constituents methanol and ethyl acetate,
nevertheless the levels of methanol never exceeded the concentrations prescribed by law [94].
Alcohols, esters, acids and aromatic compounds constituted the main group of compounds in
“koumaro” [18]. Methanol, ethyl acetate, isovaleric acid and trans-anethole were the main components
in every group, respectively [18]. In all samples studied by the authors, two of them had concentrations
of methanol higher than those permitted by law (1000 d/hL absolute alcohol) [94]. Calcium was the
main mineral in the same samples [18].
Methanol and ethyl acetate also predominated in distilled alcoholic beverages obtained from
solid-state fermentation of strawberry tree fruits from Spain [95]. In the same work, the authors
concluded that the addition of the ethanol-producing yeast (Saccharomyces cerevisiae IFI83) led to a
more efficient utilization of the reducing sugars for ethanol production than did the indigenous
microbiota of the fruits in the spontaneous fermentations [96].
Sardinian strawberry tree distillate is characterised by a lower content of C7 to C9 primary alcohols
and in general by a higher content of C6 to C10 ethyl esters and C12 to C18 fatty esters when compared
to those from Greece and Portugal [18,94,95].
The quality of distilled product may be affected by off-flavours when uncontrolled fermentations
occur, therefore the nature of yeasts present in musts contribute to the sensory characteristics [93].
These authors studied the diversity of the yeast population and the killer activity of S. cerevisiae
isolates obtained during the fermentation period of arbutus fruits from Portugal. They found a diversity
of autochthonous yeasts that fermented arbutus fruits at room temperature through a solid state
process. As fermentation progressed, a microbial succession is observed, with the final prevalence of
S. cerevisiae [93].
Molecules 2014, 19 15817
New aromatic pomegranate liquor obtained by maceration of pomegranate juice and arils from
Portuguese origins (‘Assaria’) in A. unedo distillate was performed by [97]. The authors found that
anthocyanins of pomegranate juice undergo degradation during the maceration, particularly the
monoglucosides, while ellagitannin compounds remained stable [97]. Most strawberry tree fruit spirit
volatiles (ethanal, ethyl acetate and 1-hexanol) were also detected in the liquor but in lower amounts
than in the spirit and the volatiles of pomegranate origin (limonene, 1-hexenol and trans-caryophyllene)
also had little contribution to the volatile profile of the liquor [97].
5. Conclusions
From ancient times, leaves and fruits of A. unedo L. have been used in folk medicine. Fruits have
also been used for making brandies, jams, jellies and marmalades, and less frequently eaten as fresh
fruit. The chemical composition of fruits and leaves, in which phenolic acids, flavonoids, tannins,
anthocyanins, vitamins are present, may be responsible for the reported biological properties. More
recently, the antioxidant activity of fruit extracts has also been used in meat industry to preserve the
quality and prevent oxidation of lipids and proteins. Arbutus honey has also been chemically characterized
and specific floral origin markers have been tentatively found. The biological properties of honey,
particularly the antioxidant ability, have been attributed to their phenols and even to homogentisic
acid, one of the possible chemical markers. The chemical characterization of distilled beverage obtained
from fruits of A. unedo has been established and regulated. Studies regarding the increased shelf life
periods of fruits started recently. All of these approaches have as main goal to increase the utilization
of fruits and/or derivatives in human nutrition due to their beneficial properties to human health.
Acknowledgments
Authors are grateful to FCT-Fundação para a Ciência e Tecnologia (PEst-OE/EQB/LA0023/2013).
Author Contributions
Maria G. Miguel and Adriana C. Guerreiro compiled information and wrote about chemical
composition of different parts of A. unedo. Maria L. Faleiro, Maria G. Miguel and Maria D. Antunes
compiled information and wrote about biological properties of A. unedo. Maria D. Antunes and
Adriana C. Guerreiro compiled information and wrote about the products obtained from A. unedo. All
authors read and approved the final manuscript.
Conflicts of Interest
The authors declare no conflict of interest.
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... Additionally, in Turkey, the phenological and pomological characteristics of different genotypes of the common strawberry tree and species of Greek strawberry tree have been determined [29][30][31][32] according to Celikel et al. [21]. Strawberry trees are characterized by high genetic, morphological and phenological variability [15]. ...
... In addition to soil pH, soil texture and organic matter content must also be considered to get a better estimate. It is quite adaptable to different conditions and soil types [15,25]. The microsite is determined by longitude, altitude, slope, solar radiation, air and water drainage, species diversity and other factors. ...
... The strawberry tree usually grows between 20 m and 1000 m above sea level [35], but it can grow up to 1200 m high [36]. It grows best and bears fruit when the entire plant is in full or partial sun [15,25]. The reproductive cycle of strawberry trees is much longer than that of other fruit tree species; from flowering to fruit ripening it lasts the whole year, which should be taken into account. ...
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The strawberry tree (Arbutus unedo L.) is a Mediterranean plant known for the traditional use of its fruits and leaves due to their health benefits. Thus, it has been used for years in folk medicine to relieve various health conditions such as urological and kidney problems, dermatological, cardiovascular and gastrointestinal diseases. The fruits are traditionally used for making jams, jellies, and strong alcoholic beverages, while the leaves are mostly used for preparing tea. Since leaves were more researched, previous results indicated that they have important biological effects, so further research should focus on the fruits. Due to its chemical composition, rich polyphenolic profile and the biological potential derived from it, the plant has great prospects for the production of functional foods and nutraceuticals. However, the plant’s potential is underutilized in terms of processing. Therefore, this review summarizes the properties and the potential of the fruits and leaves of A. unedo and their possible benefits for processing with respect to agricultural, nutritive, biological and economic values.
... The leaves are alternate, simple, oblanceolate, dark green, leathery and have a serrated margin. The hermaphrodite flowers are white, bell-shaped .The fruits are conspicuous, globular, orange-red when ripe (Bento and Pereira, 2011;Miguel et al., 2014;Morgado et al., 2018). In traditional folk medicine, Arbutus unedo has been used for treatment of gastrointestinal diseases, urological problems, cardiac diseases, hypertension and diabetes (Bento and Pereira, 2011;Miguel et al., 2014;Morgado et al., 2018). ...
... The hermaphrodite flowers are white, bell-shaped .The fruits are conspicuous, globular, orange-red when ripe (Bento and Pereira, 2011;Miguel et al., 2014;Morgado et al., 2018). In traditional folk medicine, Arbutus unedo has been used for treatment of gastrointestinal diseases, urological problems, cardiac diseases, hypertension and diabetes (Bento and Pereira, 2011;Miguel et al., 2014;Morgado et al., 2018). ...
... Arbutus unedo has antidiabetic, antihypertensive, antibiotic, antifungal, antiparasitic, antiaggregant, antiinflammatory, antitumoral, antioxidant, and spasmolytic properties (Bento and Pereira, 2011;Miguel et al., 2014;Morgado et al., 2018). The antihypertensive effects of aqueous extract of the root of Arbutus unedo were studied both in spontaneously hypertensive conscious rats. ...
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The incidence of hypertension is very high in human societies and its treatment is the most important priority in many countries. Knowledge of the plants that are used may provide insight on their properties, for further exploration. This study aimed to collect the knowledge on traditional medicine for the treatment of hypertension in different regions of Morocco. We reviewed 145 research publications based on data from the six explored regions of Morocco published until August 2021 in various journals. This was achieved using literature databases: Google, Google Scholar, PubMed, Medline, Science Direct and Researchgate. The findings of this study indicated that 23 plants have been reported to possess antihypertensive activities in in vivo / in vitro experiments, while 81 plants had not been studied for such an activity. Plants from the Lamiaceae, Asteraceae and Apiaceae families were used most often. Leaves were the plant parts used most often. Decoction was the main preparation method. Twenty three plants have been explored experimentally for their antihypertensive activity. This review provides baseline data for plant species used to treat hypertension in Morocco and provides new areas of research on the antihypertensive effect of these plants.
... Arbutus unedo [105]; Cistus spp. [93]; Cytinus hypocistis [62,106]; Myrtus comunis [107]; Pistacia lentiscus [108]; Teucrium genus (Germander) [22]; Cytinus. ...
... As in Table 2, nine different plants growing in Italian soil are effective against the growth of this dangerous pathogen. Among those, Arbutus unedo [105], Myrtus comunis [107] and Pistacia lentiscus [108] are certainly easy-to-find and recognized plants that could be used to improve animal welfare and help the fight against this pathogen. ...
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Drug resistance threatening humans may be linked with antimicrobial and anthelmintic resistance in other species, especially among farm animals and, more in general, in the entire environment. From this perspective, Green Veterinary Pharmacology was proven successful for the control of parasites in small ruminants and for the control of other pests such as varroa in bee farming. As in anthelmintic resistance, antimicrobial resistance (AMR) represents one of the major challenges against the successful treatment of infectious diseases, and antimicrobials use in agriculture contributes to the spread of more AMR bacterial phenotypes, genes, and proteins. With this systematic review, we list Italian plants with documented antimicrobial activity against possible pathogenic microbes. Methods: The literature search included all the manuscripts published since 1990 in PubMed, Web of Science, and Scopus using the keywords (i) “antimicrobial, plants, Italy”; (ii) “antibacterial, plant, Italy”; (iii) “essential oil, antibacterial, Italy”; (iv) “essential oil, antimicrobial, Italy”; (v) “methanol extract, antibacterial, Italy”; (vi) “methanol extract, antimicrobial, Italy”. Results: In total, 105 manuscripts that documented the inhibitory effect of plants growing in Italy against bacteria were included. One hundred thirty-five plants were recorded as effective against Gram+ bacteria, and 88 against Gram−. This will provide a ready-to-use comprehensive tool to be further tested against the indicated list of pathogens and will suggest new alternative strategies against bacterial pathogens to be employed in Green Veterinary Pharmacology applications.
... 14 This is the first report on the occurrence of ursolic acid (1) in the leaves of A. pavarii. However, related pentacyclic triterpenes were previously isolated from the fruits of another species of this genus, A. unedo, for example, α-and β-amyrin, lupeol olean-12-en-3b,23-diol. 15 Figure 5). The cytotoxic activity of ursolic acid (1) observed in the present study was more potent than any previous reports. ...
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Arbutus pavarii Pamp. (Fam. Ericaceae), an endemic Libyan medicinal plant, is commonly known as "Shmeri", "Shmar" or "Libyan Strawberry", and almost exclusively found in the Al-Jabel Al-Akhdar mountainous region in Libya. This plant is a forage species for honeybees and thus, is important for honey production. A. pavarii has long been used in Libyan traditional medicine to treat both gastritis and kidney diseases. Previous limited phytochemical studies on this plant furnished the presence of simple phenolics like arbutin and gallic acid, and polyphenolics including flavonoids and tannins, for example, apigenin, epicatechin, hesperidin, kaempferol, naringin, quercetin and rutin, as well as some triterpenes and sterols. This paper describes, for the very first time, a cytotoxicity assay-guided isolation of the major active compound from the methanol extract of the leaves of A. pavarii, and its identification as ursolic acid (1) by comprehensive spectroscopic analyses.
... Strawberry tree can also be used for honey production, biomass and tanning (Metaxas et al. 2004;Tuberoso et al. 2010). The fruits are round berries with nutritional properties (Miguel et al. 2014) used in the production of a spirit. ...
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Arbutus unedo L. is a perennial tree, native in the Mediterranean area, and tolerant to stress conditions. Due to its economic potential, there is an increasing demanding for plants by producers and farmers. In order to offer cloned material with assured quality, several micropropagation protocols have been developed, including somatic embryogenesis induction. However, little is known about this process on strawberry tree and a great deal of work is still necessary to successfully clone in A. unedo through somatic embryogenesis. Thus, the main goals of this work were: (i) to test the effect of the genotype on somatic embryogenesis induction, (ii) to analyse the role of adult and young materials on induction, and (iii) to perform a comparative histological analysis between somatic embryos and their zygotic counterparts. Somatic embryogenesis was induced on apical expanded leaves from in vitro shoots of several genotypes in Andersson medium with 3% sucrose and different concentrations of BAP (2.0 mg L⁻¹) and NAA (0.5, 1.0, 2.0, 5.0, 10.0, 15.0 and 20.0 mg L⁻¹). Embryogenesis induction rates ranged from 0 to 94.5%. Higher induction rates were achieved on the medium with 2 mg L⁻¹ BAP and 2 mg L⁻¹ NAA, and are genotype dependent. After a 3-month induction period, the highest somatic embryogenesis induction rate was 94.5% on genotype AU4. Embryos at different developmental stages were found, as well as abnormal somatic embryos. SEM images showed different anomalies being the most common embryos displaying more than two cotyledons or fused embryos. Embryo germination was not genotype dependent and the maximum embryo conversion rate achieved was 73.5%. However, only 39.21% of the embryos were able to grow into plantlets which displayed a normal chromosome number (2n = 26). Histological analysis showed differences in the cell organization between somatic and zygotic embryos, as well as several morphological anomalies. Overall, the developed somatic induction protocol proved to be very efficient, with high induction rates achieved, both from seedling and adult material, but its genotype dependent. However, embryo conversion still needs to be improved, in order to fully seize the potential of this micropropagation technique.
... The chemical makeup of various components of the plant, as well as strawberry tree honey and strawberry tree brandy, will be discussed. The biological characteristics of A. unedo's various components, as well as strawberry tree honey, will be discussed [10]. ...
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A wide range of plants have benefited from rapid technological advancements in controlled environment (CE) plant production. Because of their excellent economic and nutritional benefits, strawberries have been a popular crop for CE production in recent years. Growers may control strawberry growth and development by supplying particular light spectra thanks to the extensive usage of light-emitting diode (LED) technology in the produce sector. Strawberry secondary metabolism may be influenced by varying light intensity and spectral composition, which has a significant effect on fruit quality and antioxidant qualities. While the effect of visible light on secondary metabolite profiles in other greenhouse crops has been well established, further research into the impact of various light spectra on strawberry plants, ranging from UV radiation to visible light, is needed. Growers will be able to optimize production and quickly react to changing customer tastes as a result of this. This article presents a comparison of how light spectrum affects strawberry photobiology and secondary metabolism, as well as a collection of research examining the effect of light characteristics on strawberry fruit flavonoids. The impacts of UV and visible light pre-harvest and post-harvest light treatments are examined. Future study and consequences for researchers and farmers of LED lighting setups in strawberry fruit production are addressed.
... On the other hand, if we evaluate the species Arbutus unedo L., mostly flavonoids such as quercetin, anthocyanins (cyanidin and delphinidin glycosides), among others, are identified. In addition to these, hydroxybenzoic acids such as gallic acid were the main phenolic compounds reported and, in minor concentrations, chlorogenic acid was also found [47][48][49]. Flavonoids are able to modulate enzyme activity, and, for this reason, they are the main class of phenolic compounds that exhibit the strongest antioxidant activity. Therefore, it is justified that the species Arbutus unedo L. is more toxic to the enzyme and has the lowest IC 50 [50][51][52]. ...
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The aim of this study is the development of an automated method for myeloperoxidase activity evaluation and its application in testing the inhibitory action of different plant extracts on the activity of the enzyme. This enzyme has its concentration increased in inflammatory and infectious processes, so it is a possible target to limit these processes. Therefore, an automatic sequential in-jection analysis (SIA) system was optimized and demonstrated that it is possible to obtain results with satisfactory accuracy and precision. With the developed method, plant extracts were studied, as promising candidates for MPO inhibition. In the group of selected plant extracts, IC50 values from 0.029 ± 0.002 mg/mL to 35.4 ± 3.5 mg/mL were obtained. Arbutus unedo L. proved to be the most inhibitory extract for MPO based on its phenolic compound content. The coupling of an automatic SIA method to MPO inhibition assays is a good alternative to other conventional methods, due to its simplicity and speed. This work also supports the pharmacological use of these species that inhibit MPO, and exhibit activity that may be related to the treatment of infection and inflammation.
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Arbutus unedo L. is a species with great economic impact in rural areas, and its fruits have several food applications and beneficial properties on human health. However, the fruits are highly perishable, and little is known about their characteristics. The present work thus aimed to evaluate the physicochemical and microbiological parameters of Arbutus unedo L. during two consecutive years from four different samples. Microbiological analysis was conducted at different times of preservation (days 0, 4, 11, and 21) and temperatures (room temperature, refrigeration, and freezing). Six fungal strains as representatives of the most prevalent mycobiota in fruits were used for molecular identification. The fruits had aw values of 0.916 ± 0.01 to 0.930 ± 0.01, pH values of 3.81 ± 0.01 to 3.82 ± 0.01, and ºBrix values of 25.02 ± 0.49 to 28.52 ± 1.02. Microbiological analysis revealed that the predominant microbiota in fresh fruits were psychrotrophs (4.07 ± 0.25 log CFU/g), yeasts (3.39 ± 0.18 log CFU/g), mesophiles (3.26 ± 1.20 log CFU/g), and moulds (2.70 ± 0.55 log CFU/g). After a preservation period of 11 days, the microbial loads increased from 66 to 116% at 25 ± 1°C; while at 6.5 ± 1°C, the increase varied from 3 to 53%; except for moulds, for which a decrease was observed. The application of freezing temperature (21 days) showed a small increase for psychrotrophs and yeasts of 1.5 and 2.9%, respectively. The most prevalent moulds identified belonged to Rhizopus stolonifer var. stolonifer, Aspergillus carbonarius, and Penicillium brevicompactum, while yeasts belonged to Aureobasidium sp. and Saccothecium rubi.
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This study attempts to investigate physicochemical and antibacterial properties of kefir enriched with freeze‐dried Arbutus unedo L. and Tamarindus indica L. fruits and sweetened using stevia, monk fruit sweetener, aspartame, and sucrose (beet and cane sugar). Based on the findings of the study, the pH values of kefir decreased with the addition of fruits. The lowest syneresis and the highest dry matter values were found in the samples with sucrose. 15 phenolic compounds and 31 amino acids were detected using LC‐MS/MS. The major phenolic components of the samples added with Arbutus unedo L. and Tamarindus indica L. fruits were gallic acid and syringic acid, respectively. Only gallic, protocatechuic, salicylic, and caffeic acids were detected in the control sample (C1). The primary amino acids were L‐proline, L‐glutamic acid, and L‐valine, respectively. Kefir and fruit samples demonstrated antibacterial effect against Bacillus cereus, Staphylococcus aureus, and Escherichia coli.
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The plant kingdom is an endless source of molecules that can be applied in almost all realms of society. The food industry has profited from the use of plants and their derived materials for many decades. Recently, the food industry has been looking into plants to find different ways of either preserving, coloring or sweetening foods. In this work, leaf extracts of Arbutus unedo L. obtained by dynamic maceration and ultrasound assisted extraction with prior optimization of their extraction conditions through the response-surface methodology, were incorporated in quark cheese as natural preservatives and analyzed over 8 days of shelf-life. Both extracts showed antioxidant activity with no toxicity towards primary cell lines at the maximum tested concentration, as well as antibacterial activity, especially against Gram-positive strains. After their incorporation in quark cheese, no significant changes were observed in the nutritional profile and physical traits of the quark cheeses, while the microbial load was highly reduced in the cheese, especially using the extracts obtained from dynamic maceration. Thus, leaf extracts of A. unedo can be promising candidates for use in the food industry as natural preservatives.
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The typical profile of the free amino acids contained in strawberry-tree (Arbutus unedo L.) honey is reported for the first time. An optimized reversed-phase liquid chromatographic (RP-LC) method with phenyl isothiocyanate precolumn derivatization was used. Fourteen free amino acids were identified and quantified in 16 analytical samples. Proline (65.63) was found to be the most abundant free amino acid, followed by glutamic acid (6.49), arginine (5.21), alanine (5.17), and phenylalanine (4.97). The total free amino acid content of strawberry-tree honey (average value, 436 mg/kg) was found to be low in comparison to amounts cited in the literature concerning unifloral honeys. The analytical method was optimized and fully validated in terms of detection and quantitation limits, precision (by testing repeatability and reproducibility), linearity, and bias (by means of recovery tests). The acceptability of the validation protocol results was verified using Horwitz's mathematical model and AOAC guidelines.
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This study was carried out to investigate the nutrient composition of some wild fruit species such as English hawthorn (Crateagus oxyacantha), common barberry (Berberis vulgaris), sea backthorn (Hippophae rhamnoides), rowanberry (Sorbus aucuparia), wild strawberry (Fragaria vesca), cornelian cherry (Cornus mas), Japanese persimmon (Diospyros lotus), medlar (Mespilus germanica) and strawberry tree (Arbutus unedo) grown naturally in Northeastern Anatolia. Some properties of these species, including % moisture, protein, ash, total dry matter, total soluble solids, total sugar, reducing sugar, ascorbic acid, total acidity, pH and some minerals (P, K, Ca, Mg, Fe, Cu, Zn, Mn) were determined. Results of this study showed that the nutritional values of the wild fruit species investigated were considerably high, therefore, it can be suggested that these species should be cultured to have more benefit.
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The genus Arbutus (fam.: Ericaceae) is represented by two species, A. unedo L. and A. andrachnae L., in the flora of northwestern Turkey. The Çanakkale region located in northwestern Turkey is one of the main locations for Arbutus species. The main objective of the present study is to present some phenological, plant and fruit characteristics of the Arbutus population. During the study, flowering time, average canopy size, tree height, trunk diameter and fruit yield were determined. Besides plant characteristics some chemical properties including pH, soluble solid content (TSS), titratable acidity (TA), ascorbic acid, anthocyanins and minerals were determined in fully mature Arbutus unedo L. and Arbutus andrachnae L. fruits collected from different sites of Çanakkale-Turkey. Preliminary results of A. unedo fruit storage are presented. Based on the plant characteristics and chemical composition, cultivation of this underutilized crop is recommended.
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Essential oils isolated by hydrodistillation from flower and fruit of Arbutus unedo growing in Turkey were analyzed by GC and GC/MS. Forty-nine compounds, representing around 95% of the total oils were identified. Non-terpenoids hydrocarbons were shown to be the main group of constituents of the flower and fruit part of the plant in the ratio of 62.2 and 92.8%, respectively. The major component in the essential oil of the flower was α-terpineol (16.3%) and the main compound in the essential oil of the fruit was hexadecanoic acid (21.7%). The antimicrobial activity of the isolated essential oils of the flower and fruit were also investigated and it showed moderate antibacterial activity against Listeria monocitogenes and Enterococcus faecalis.
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The effect of adding artichoke (Cynara scolymus L.), strawberry-tree fruit [Arbutus unedo L.) and cherry [Prunus avium L.) extracts was evaluated on the physico-chemical, antioxidant and microbiological properties of homemade yogurts. Yogurts, enriched with artichoke or red ripe strawberry-tree fruit extract, demonstrated high in vitro antioxidant activity. ten days after their preparation, no variations in the antioxidant components and antioxidant activity of the yogurts were observed. the enriched yogurts showed an increase in lactic acid and acetaldehyde. As regards microbial characteristics, there was a notable increase in the microbial count of Lactobacilli in yogurts with edible artichoke parts (4.5×109 cfu/g) and with strawberry-tree fruit extracts (1.8×109 cfu/g) during the threeweek experimental period. During the same period persistence of streptococci in yogurt with artichoke edible parts was observed until the end of the first week (5.2×107 cfu/g). our results indicate that the enrichment of yogurts with sardinian plant extracts can significantly improve the antioxidant activity of yogurt and in some cases the survival of its microbial flora.
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The plant species Arbutus unedo shows numerous beneficial pharmacological effects (antiseptic, antidiabetic, antidiarrheal, astringent, depurative, antioxidant, antihypertensive, antithrombotic, and anti-inflammatory). For the medicinal use, standardization of extracts is a necessity, as different compounds are responsible for different biological activities. In this paper, we analyze monthly changes in the content of quercitrin, isoquercitrin, hyperoside, and chlorogenic acid. Methanolic extracts of the leaves are analyzed by HPTLC for the identification and quantification of individual polyphenol, and DPPH test is used to determine antioxidant activity. Based on the results obtained, the leaves should be collected in January to obtain the highest concentrations of hyperoside and quercitrin (0.35 mg/g and 1.94 mg/g, resp.), in June, July, and October for chlorogenic acid (1.45–1.46 mg/g), and for the fraction of quercitrin and isoquercitrin in November (1.98 mg/g and 0.33 mg/g, resp.). Optimal months for the collection of leaves with the maximum recovery of individual polyphenol suggested in this work could direct the pharmacological usage of the polyvalent herbal drugs.
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In the fruits of two different genotypes (57A1 and 57A22) of Turkish strawberry trees (Arbutus unedo L.) dried at 70 and 80°C in a computer connected parallel air flow type drier, fruit weight, fruit color and vitamin C were determined. In this study, it was determined that drying increased losses of fruit weight and Vitamin C, and soluble solid content and also colour variations in dried fruits occurred. In both genotypes, the drying at 70°C temperature was better than 80°C in terms of fruit weight, vitamin C, soluble solids and colour.
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Arbutus unedo leaf is used traditionally for gastrointestinal complaints. Ethanol extracts from Arbutus unedo collected in both Montenegro (AuM) and Greece (AuG) were found to decrease the ileal basal tonus, with AuG producing a significantly higher (p < 0.05) reduction in contractile response to acetylcholine. AuM and AuG relaxed 80 mM K(+) induced contractions and shifted the Ca(++) concentration-response curves to the right, similar to that caused by verapamil, suggesting that the spasmolytic effect was induced through calcium channel inhibition. The antioxidant activity of AuM and AuG and the phenolic content of the extracts and dry plant material were studied, and both extracts were found to possess considerable antioxidant properties. AuG showed a stronger in vitro antioxidative activity in the DPPH assay and in the TBA test. Polyphenol, tannin and flavonoid levels were higher in AuG, supporting the more potent spasmolytic and antioxidative effects, whereas the arbutin content was higher in dry plant material collected in Montenegro.