Arbutus unedo, commonly known as the strawberry tree, is an evergreen shrub or small tree distinguished by its red, strawberry-like fruits and delicate, bell-shaped white to pink flowers. Native to the Mediterranean region and parts of Western Europe, Arbutus unedo is valued both for its ornamental appeal and its edible fruits, often used in traditional recipes. In folk medicine, this plant is recognized for its potential antioxidant, diuretic, and anti-inflammatory properties.

Botanical Classification

• Kingdom: Plantae
• Clade: Tracheophytes
• Class: Magnoliopsida
• Order: Ericales
• Family: Ericaceae
• Genus: Arbutus
• Species: Arbutus unedo

Plant Characteristics

Arbutus unedo is a slow-growing, evergreen shrub or small tree that can reach heights of 5–10 meters. It has dark green, leathery, serrated leaves and produces clusters of small, bell-shaped flowers in autumn. The flowers, which range from white to pink, often appear alongside the fruits, creating an attractive display. The fruits are round, red, and bumpy, resembling strawberries. They take about a year to mature, transitioning from green to orange and then to bright red when fully ripe.

Chemical Composition and Structure

The various parts of Arbutus unedo, particularly its fruits, leaves, and bark, contain bioactive compounds that contribute to its medicinal and nutritional properties:

• Antioxidants: Polyphenols and flavonoids, which help combat oxidative stress and protect cells from free radical damage.

• Arbutin: A phenolic glycoside primarily found in the leaves, known for its antimicrobial and skin-brightening properties, used in some skincare treatments.

• Tannins: Astringent compounds that may offer anti-inflammatory effects and have been used in traditional remedies for gastrointestinal issues.

• Organic Acids: Including malic and citric acids, which contribute to the slightly tart flavor of the fruits and aid digestion.

• Vitamins and Minerals: Contains vitamin C and other nutrients that support immune health and add to the fruit’s nutritional value.

How to Cultivate Arbutus unedo

Cultivating Arbutus unedo requires some specific conditions to encourage healthy growth and flowering:

1. Climate: Thrives in Mediterranean climates with hot, dry summers and mild winters. It is tolerant of light frost but may suffer in extremely cold regions.

2. Soil Requirements: Prefers well-drained, acidic to neutral soils rich in organic matter. It can also tolerate poorer, rocky soils.

3. Propagation: Can be propagated from seeds, which require cold stratification to enhance germination, or by hardwood cuttings in autumn.

4. Watering and Maintenance: Once established, it is relatively drought-tolerant. Regular watering is needed during the first year of growth. Light pruning is beneficial to remove dead or damaged branches and to shape the plant.

5. Harvesting: Ripe fruits are harvested in autumn. Leaves can be collected for medicinal uses.

Uses and Benefits

In traditional medicine and folk practices, Arbutus unedo is known for its various benefits:

• Antioxidant Properties: The polyphenols in the fruits and leaves help combat free radicals and protect cells from premature aging.

• Diuretic Action: Traditionally used to promote urination and aid in the elimination of toxins through urine, supporting kidney health.

• Anti-inflammatory Properties: The tannins in the leaves and bark may help reduce inflammation, useful for treating gastrointestinal disorders and other internal inflammations.

• Skin Health: Due to the presence of arbutin, strawberry tree leaves are used in natural skin treatments for their skin-brightening and antibacterial effects.

• Edible Fruits: The fruits are edible and are used in jams, liqueurs, and traditional sweets. Their mildly sweet and slightly tart flavor makes them suitable for preserves.

Applications

• Medical: Used in traditional herbal remedies, particularly in teas and infusions, for diuretic, anti-inflammatory, and antioxidant properties. It is common in herbal teas to support renal and urinary health.

• Cosmetic: Extracts of Arbutus unedo, particularly from the leaves, are used in some skincare products for their skin-brightening and purifying properties.

• Culinary: The fruits are consumed fresh or used to make jams, liqueurs, and traditional desserts. The strawberry tree is also an ingredient in Mediterranean cuisine for making preserves.

• Ornamental: Arbutus unedo is widely grown as an ornamental plant in gardens and parks for its attractive flowers and fruits, which add color and interest in autumn and winter.

Environmental and Safety Considerations

Arbutus unedo is generally safe for human use and can be consumed both topically and in food. However, excessive intake of the fruits may cause mild gastrointestinal discomfort due to the tannin content. It is an ecologically sustainable plant, drought-resistant, and adaptable to different soil types, requiring low maintenance once established. It is not invasive and contributes positively to biodiversity in the environment. As with any plant, individuals with specific allergies should use caution when handling products containing Arbutus unedo.

Studies

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

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.

Read more:

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.