Compendium of the most significant studies with reference to properties, intake, effects.

Karatassiou M, Karaiskou P, Verykouki E, Rhizopoulou S. Hydraulic Response of Deciduous and Evergreen Broadleaved Shrubs, Grown on Olympus Mountain in Greece, to Vapour Pressure Deficit. Plants (Basel). 2022 Apr 8;11(8):1013. doi: 10.3390/plants11081013. 

Abstract. In this study, leaf hydraulic functionality of co-occurring evergreen and deciduous shrubs, grown on Olympus Mountain, has been compared. Four evergreen species (Arbutus andrachne, Arbutus unedo, Quercus ilex and Quercus coccifera) and four deciduous species (Carpinus betulus, Cercis siliquastrum, Coronilla emeroides and Pistacia terebinthus) were selected for this study. Predawn and midday leaf water potential, transpiration, stomatal conductance, leaf temperature and leaf hydraulic conductance were estimated during the summer period. The results demonstrate different hydraulic tactics between the deciduous and evergreen shrubs. Higher hydraulic conductance and lower stomatal conductance were obtained in deciduous plants compared to the evergreens. Additionally, positive correlations were detected between water potential and transpiration in the deciduous shrubs. The seasonal leaf hydraulic conductance declined in both deciduous and evergreens under conditions of elevated vapor pressure deficit during the summer; however, at midday, leaf water potential reached comparable low values, but the deciduous shrubs exhibited higher hydraulic conductance compared to the evergreens. It seems likely that hydraulic traits of the coexisting evergreen and deciduous plants indicate water spending and saving tactics, respectively; this may also represent a limit to drought tolerance of these species grown in a natural environment, which is expected to be affected by global warming.

Scarano P, Guida R, Zuzolo D, Tartaglia M, Prigioniero A, Postiglione A, Pinto G, Illiano A, Amoresano A, Schicchi R, Geraci A, Sciarrillo R, Guarino C. An Endemic Plant of the Mediterranean Area: Phytochemical Characterization of Strawberry Tree (Arbutus unedo L.) Fruits Extracts at Different Ripening Stages. Front Nutr. 2022 Jun 17;9:915994. doi: 10.3389/fnut.2022.915994. 

Abstract. This work focused on the extraction, quantification, and characterization of bioactive compounds of Arbutus unedo L. fruits, comparing the results obtained from the different ripening states. Extractions were performed by different methods (such as maceration extraction and ultrasonic extraction) and food grade solvents (aqueous and hydroalcoholic solvents) in each of the all ripening states (four states considered, associated with four different colors, i.e., green, yellow, orange, and red). The presence of (poly)phenols was quantified and characterized, and scavenging activity was determined by the Folin-Ciocâlteu reagent and the DPPH method, respectively. The content of bioactive compounds was characterized by LC-MS/MS, such as multiple reaction monitoring (MRM) mass spectrometry. The results showed that ultrasound-assisted extraction (UAE) performed better than maceration extraction; ethanol-water mixture extracts showed a more positive effect than the use of aqueous extracts regarding the content of total phenolic compounds. Overall, the total phenolic compounds in the EtOH:H2O mixture at a ratio of 7:3 (v:v) were higher than that of the other solvents for both extraction methods. Some bioactive molecules were characterized for the first time in the extracts of A. unedo. The chemical profile of the strawberry tree extracts depended on the degree of fruit ripeness. The results suggest that A. unedo fruits may be of great interest for food and nutraceutical applications. Copyright © 2022 Scarano, Guida, Zuzolo, Tartaglia, Prigioniero, Postiglione, Pinto, Illiano, Amoresano, Schicchi, Geraci, Sciarrillo and Guarino.

Koukos, D., Meletiou-Christou, M. S., & Rhizopoulou, S. (2015). Leaf surface wettability and fatty acid composition of Arbutus unedo and Arbutus andrachne grown under ambient conditions in a natural macchia. Acta Botanica Gallica, 162(3), 225-232.

Abstract...The objective of this work was to study and compare leaf surface morphology and wettability of Arbutus unedo L. and Arbutus andrachne L., as well as the fatty acid composition of leaf lipids, as part of a larger study of leaf wettability of Mediterraenan plants (Kolyva et al. 2012; Fernández et al. 2014; Razeq et al. 2014). Arbutus unedo L. and A. andrachne L. belong to the Ericaceae family, and are relatively widespread in the Mediterranean region (Hileman, Vasey, and Parker 2001; Baslar, Dogan, and Mert 2002; Blondel et al. 2010). The strawberry tree, A. unedo, is a perennial, drought-tolerant evergreen, which is capable of regenerating after forest fires (Savé et al. 1993). The appearance of both fruits and flowers in late autumn and during the winter give the strawberry tree ornamental importance (Celikel, Demirsoy, and Demirsoy 2008; Oliveira et al. 2011); also, the edible fruits of A. unedo contain phenolic and antioxidant substances, and can be used to produce jams, jellies and alcoholic beverages (Ayaz, Kucukislamoglu, and Reunanen 2000; Bouzid et al. 2014; Cavuşoğlu, Sulusoglu, and Erkal 2015). The oriental strawberry tree, A. andrachne, is a perennial evergreen that differs from A. unedo in lamina and panicle positions (Serçe et al. 2010); its fruits are smaller than those of A. unedo, but are of similar shape and colour. Arbutus andrachne is not cultivated, unlike A. unedo....

Maleš Z, Sarić D, Bojić M. Quantitative Determination of Flavonoids and Chlorogenic Acid in the Leaves of Arbutus unedo L. Using Thin Layer Chromatography. J Anal Methods Chem. 2013;2013:385473. doi: 10.1155/2013/385473.

Abstract. 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.

Tenuta MC, Deguin B, Loizzo MR, Dugay A, Acquaviva R, Malfa GA, Bonesi M, Bouzidi C, Tundis R. Contribution of Flavonoids and Iridoids to the Hypoglycaemic, Antioxidant, and Nitric Oxide (NO) Inhibitory Activities of Arbutus unedo L. Antioxidants (Basel). 2020 Feb 22;9(2):184. doi: 10.3390/antiox9020184.

Abstract. This study aims at investigating the contribution of two classes of compounds, flavonoids and iridoids, to the bioactivity of Arbutus unedo L. leaves and fruits. The impact of different extraction procedures on phytochemicals content and hypoglycemic, antioxidant, and nitric oxide (NO) inhibitory activities of A. unedo fresh and dried plant materials was investigated. Ellagic acid 4-O-β-D-glucopyranoside, kaempferol 3-O-glucoside, and norbergenin were identified for the first time in this genus by using liquid chromatography-electrospray ionization-quadrupole-time of flight-mass spectrometry (LC-ESI-QTOF-MS). Three iridoids (gardenoside, geniposide, unedoside) are specifically identified in the leaves. Interestingly, asperuloside was extracted only from dried fruits by ethanol with Soxhlet apparatus. Extracts were screened for their potential antioxidant activities by using the 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), 2,2-diphenyl-1-picrylhydrazyl (DPPH), Ferric Reducing Activity Power (FRAP), and β-carotene bleaching tests. Based on the Global Antioxidant Score (GAS) calculation, the most promising antioxidant extract was obtained by hydroalcoholic maceration of dried leaves that showed half maximal inhibitory concentration (IC50) of 0.42 and 0.98 μg/mL in ABTS and DPPH assays, respectively. The hypoglycaemic activity was investigated by α-amylase and α-glucosidase inhibition tests. Extracts obtained by ethanol ultrasound extraction of fresh leaves and hydroalcoholic maceration of fresh fruits (IC50 of 19.56 and 28.42 μg/mL, respectively) are more active against α-glucosidase than the positive control acarbose (IC50 of 35.50 μg/mL). Fruit extracts exhibited the highest anti-inflammatory activity.

Safety

Jurica K, Benković V, Sikirić S, Brčić Karačonji I, Kopjar N. The effects of strawberry tree (Arbutus unedo L.) water leaf extract and arbutin upon kidney function and primary DNA damage in renal cells of rats. Nat Prod Res. 2020 Aug;34(16):2354-2357. doi: 10.1080/14786419.2018.1534106. 

Abstract. Although strawberry tree (Arbutus unedo L.) leaves have long been used as a herbal remedy, insufficient information is available on their nephrotoxicity. We assessed the safety of strawberry tree water leaf extract and its key component arbutin, administered per os to Lewis rats of both genders at 200 mg/kg b.w./day for 14 and 28 days. The effects of the tested compounds on DNA integrity in renal cells was evaluated using alkaline comet assay, while kidney function was studied using serum creatinine and urea levels. Strawberry tree water leaf extract showed high biocompatibility with kidney tissue. It did not impair DNA integrity of renal cells and kidney function, either in male or female rats. However, exposure to single arbutin affected the levels of primary DNA damage in renal cells which could be related to metabolic conversion of arbutin into hydroquinone, whose nephrotoxicity has previously been proven.

Arbutus unedo Leaf Water is an aqueous solution obtained from the evergreen plant Arbutus unedo L. (Strawberry tree) belonging to the Ericaceae family, which is distributed in the Mediterranean area. The fruits are used for the preparation of jams, infusions and liqueurs. The strawberry tree is also used to produce a bitter-tasting honey. It is a plant that reaches and exceeds a height of 3 metres.

What it is used for and where

Medical

In traditional medical science, the fruits and leaves of Arbutus unedo have been used as diuretics, antiseptics, laxatives and to treat high blood pressure. 

In the phytochemical composition of the fruits we find (1)

• phenolic compounds: gallic acid, protocatechuic acid, gentisic acid, p-hydroxybenzoic acid, vanillic acid, catechin, procyanidin, ellagic acid 
• unsaturated fatty acids: α-linolenic (36%), linoleic (21%) and oleic (21%)
• saturated fatty acids: palmitic acid (8%)
• vitamins: vitamin E, α-, β-, γ- and δ-tocopherol and α-tocotrienol, vitamin C
• sugars: fructose and glucose

In the phytochemical composition of the leaves we find

phenolic compounds: arbutin (hydroquinone β-glucoside), chlorogenic acid, quercitrin, isoquercitrin

• flavanols: catechins
• flavonols: quercetin, kaempferol
• vitamins: α-tocopherol

In the phytochemical composition of the root we find:

• flavanols: catechins
• phenolic compounds: benzoic acid, caffeic acid, gallic acid

Now let us see what properties and contraindications are attributed to this plant by the scientific literature: antioxidant activity in the fruit and leaves, anti-fungal activity in the leaves, anti-inflammatory activity in the leaves, antibacterial activity in the root. However, it should be borne in mind that all these properties are conditioned by important factors that determine their quality and effectiveness: harvest time, climate, possible environmental pollution and more.

Food safety

Arbutin is the phenolic component of the leaves that has shown antioxidant activity and a low potential for DNA damage, but it seems to be understood that excessive doses of this component could somehow have an undesirable effect (2).

Cosmetics

INCI Functions:

Skin conditioning agent. It is the mainstay of topical skin treatment as it has the function of restoring, increasing or improving skin tolerance to external factors, including melanocyte tolerance. The most important function of the conditioning agent is to prevent skin dehydration, but the subject is rather complex and involves emollients and humectants that can be added in the formulation.

Skin conditioning agent - Emollient. Emollients have the characteristic of enhancing the skin barrier through a source of exogenous lipids that adhere to the skin, improving barrier properties by filling gaps in intercorneocyte clusters to improve hydration while protecting against inflammation. In practice, they have the ability to create a barrier that prevents transepidermal water loss.  Emollients are described as degreasing or refreshing additives that improve the lipid content of the upper layers of the skin by preventing degreasing and drying of the skin. The problem with emollients is that many have a strong lipophilic character and are identified as occlusive ingredients; they are oily and fatty materials that remain on the skin surface and reduce transepidermal water loss. In cosmetics, emollients and moisturisers are often considered synonymous with humectants and occlusives.

The antifungal activity of phenolic compounds is useful in cosmetic formulations to prevent fungal formations from attacking the product over time. The antioxidant activity helps with preservation.

CAS     84012-12-4

EC number    281-657-2

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Arbutus unedo studies

References_____________________________________________________________________

(1) Miguel MG, Faleiro ML, Guerreiro AC, Antunes MD. Arbutus unedo L.: chemical and biological properties. Molecules. 2014 Sep 30;19(10):15799-823. doi: 10.3390/molecules191015799. 

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.

(2) Jurica K, Brčić Karačonji I, Mikolić A, Milojković-Opsenica D, Benković V, Kopjar N. In vitro safety assessment of the strawberry tree (Arbutus unedo L.) water leaf extract and arbutin in human peripheral blood lymphocytes. Cytotechnology. 2018 Aug;70(4):1261-1278. doi: 10.1007/s10616-018-0218-4. 

Abstract. Strawberry tree (Arbutus unedo L.) leaves have long been used in the traditional medicine of the Mediterranean region. One of their most bioactive constituents is the glycoside arbutin, whose presence makes A. unedo suitable as a potential substitute for bearberry [Arctostaphylos uva ursi (L.) Spreng] leaves, an herbal preparation widely used for treating urinary tract infections. The safety and biocompatibility of strawberry tree water leaf extract have not yet been documented well. This study estimated arbutin content in strawberry tree water leaf extract (STE) using high performance liquid chromatography. Furthermore, we performed an in vitro safety assessment of the 24 h exposure to three presumably non-toxic concentrations of standardized STE and arbutin in human peripheral blood lymphocytes using the apoptosis/necrosis assay, the alkaline comet assay, and the cytokinesis-block micronucleus cytome assay. The STE was also tested for total antioxidant capacity and lipid peroxidation. At a concentration corresponding to the maximum allowable daily intake of arbutin, the tested extract was not cytotoxic, had a negligible potential for causing primary DNA damage and even hindered micronuclei formation in lymphocytes. It also showed a valuable antioxidant capacity, and did not exert marked lipid peroxidation. These promising results represent a solid frame for further development of STE-based herbal preparations. Although arbutin generally had a low DNA damaging potential, the slowing down of lymphocyte proliferation observed after 24 h of exposure points to a cytostatic effect, which merits further research.

Jurica K, Benković V, Sikirić S, Brčić Karačonji I, Kopjar N. The effects of strawberry tree (Arbutus unedo L.) water leaf extract and arbutin upon kidney function and primary DNA damage in renal cells of rats. Nat Prod Res. 2020 Aug;34(16):2354-2357. doi: 10.1080/14786419.2018.1534106. 

Abstract. Although strawberry tree (Arbutus unedo L.) leaves have long been used as a herbal remedy, insufficient information is available on their nephrotoxicity. We assessed the safety of strawberry tree water leaf extract and its key component arbutin, administered per os to Lewis rats of both genders at 200 mg/kg b.w./day for 14 and 28 days. The effects of the tested compounds on DNA integrity in renal cells was evaluated using alkaline comet assay, while kidney function was studied using serum creatinine and urea levels. Strawberry tree water leaf extract showed high biocompatibility with kidney tissue. It did not impair DNA integrity of renal cells and kidney function, either in male or female rats. However, exposure to single arbutin affected the levels of primary DNA damage in renal cells which could be related to metabolic conversion of arbutin into hydroquinone, whose nephrotoxicity has previously been proven.