ARBUTUS UNEDO
ERICACEAE
The strawberry tree is a small tree or shrub native to the western Mediterranean region (North Africa, Iberian Peninsula, France, Italy) but which acclimatizes easily and can become invasive (e.g. in the Canary Islands). It is now present in the eastern Mediterranean countries, in central Europe and as far as Russia.
It is related to heather.
It is a useful and medicinal tree, resistant to drought and fires but can also grow in humid regions close to the Ocean (France, Ireland, England).
It is also a decorative tree with evergreen foliage that can be pruned, its fruits are edible and its flowers are very useful to bees in autumn.
Arbutus unedo reaches a variable size depending on the quality of the soil and its humidity. In good conditions it can reach about ten meters but most often only 3-5 meters. The upper part of the branches can be reddish, the often short trunk is grayish. The evergreen leaves are alternate, green on top and generally whitish underneath. The white flowers are in clusters, similar to small bells (like many ericaceae). They do not appear in spring but at the end of the year (autumn-winter) and are present on the tree with the fruits of the previous year.
The spherical fruits are yellow-orange or red when ripe and are covered with a rough skin with small conical tips; It is an easily recognizable fruit, it ripens in winter, its edible flesh is floury, soft when ripe, slightly sweet and acidic, it contains very small brown or black seeds.
The strawberry tree is medicinal by its fruit, its leaves and its roots.
CHEMICAL COMPOSITION AND PROPERTIES
ARBUTUS UNEDO FRUIT
The chemical composition of the fruit depends on many parameters: the level of ripeness of the fruit, the crop variety, climatic conditions and the nature of the soil.
However, we can simplify and give an average value of the chemical composition of fully ripe and partially dehydrated (freeze-dried) fruits:
Water (10%), sugars (60%), fiber (16%), lipids (4%), proteins (3%), mineral ash (2%), vitamin C (200 to 400mg/100g, vitamin E (between 30 and 300mg/100g of alpha-tocopherol), minerals (especially calcium, potassium, phosphorus and magnesium), organic acids in small quantities (citric, malic, oxalic, fumaric).
These are average values, and it should be noted that fresh ripe fruit contains much more water (60 to 80%).
Sugars are mainly glucose and fructose, lipids are mainly unsaturated fatty acids (alpha linolenic, linoleic and oleic).
Average energy value for the (dehydrated) fruit of the strawberry tree: 350 Kcal per 100 g
It is therefore a nourishing fruit which provides vitamins and mineral salts.
Pharmacologists are particularly interested in the fruit’s content of phenolic substances, which are abundant, varied, and known for their anti-inflammatory, antioxidant, antibiotic, antidiabetic, and blood pressure-regulating properties. These are pigments (anthocyanins), flavonoids, and medicinal tannins.
ARBUTUS UNEDO STRAWBERRY LEAVES: ARBUTIN and skin lightening
The leaves contain medicinal flavonoids and tannins, but it is mainly the presence of a hydroquinone derivative (associated with glucose) that interests pharmacologists because it has medical applications.
This is ARBUTIN, present in many plants (including the leaves of the common pear, Pyrus communis and Arctostaphylos uva-ursi (Arbutus uva-ursi) = bearberry).
Arbutin is less toxic than hydroquinone; it slows down the synthesis of melanin (dark pigment) by melanocytes located in the deep layer of the skin. The result is a lightening of the skin color. This is a highly sought-after effect, particularly in Asian populations (while Europeans tan!), and it is also useful for reducing hyperpigmented spots that appear as we age.
Hydroquinone is apparently more effective, but it is a toxic substance (which can destroy melanocytes) causing dermatitis, permanent, sometimes irregular depigmentation, and it is an environmental toxin.
Arbutin has a gentler action, and if hydroquinone is released into the skin, it is in small quantities.
ARBUTIN and pharmacology research
Fatty degeneration of the liver not related to alcoholism (hepatic steatosis) is a fairly common problem that has no specific treatment. There is mortality of liver cells (hepatocytes); It would seem that this mortality is caused by the phenomenon of ferroptosis which is one of the modalities of natural programmed cell death.
Arbutin seems to oppose this ferroptosis which follows many complex inflammatory reactions at the cellular level and could therefore slow the degeneration of the liver which is a very important gland in our body.
Recent studies show that arbutin inhibits liver cancer in animals and has anticancer properties in vitro on cancer cell cultures of various origins.
At high doses, arbutin becomes toxic (liver and kidney).
ROOTS OF THE ARBUTUS UNEDO TREE
The roots contain catechins, flavonoids quite similar to tannins.
Catechins have an antidiabetic effect; they are inhibitors of intestinal alpha-glucosidases.
In traditional medicine, strawberry tree root extracts are used to lower blood pressure.
USES
STRAWBERRY TREE FRUIT
It is an edible, nutritious, and vitamin-rich fruit when fully ripe, but it is not very « tasty. »
It is more popular for making jams or fruit paste.
Excessive consumption of fresh strawberry tree fruit can cause digestive discomfort, colic, and diarrhea.
Example of preparation of strawberry tree jams or fruit pastes:
-Strawberry tree jellies: put the washed fruit in a saucepan, cover with water, bring to a boil then keep on low heat for 15 to 30 minutes, the liquid will turn pink, remove the fruit without bursting it, add 700g of sugar per liter of liquid, bring to a boil while watching the preparation thicken, put in a jar.
-Simple strawberry tree jam: cook the fruit in water for 15 minutes, turn off the heat and let it cool for 2 hours; Remove the cooked fruit and press it through a fine mesh filter , add 700g of sugar plus a lemon juice to the liquid obtained, cook again, keeping an eye on it because the jam can sometimes thicken quickly (10 to 15 minutes), put it in a jar or spread it into a thin layer which will be dried in a low oven to obtain a fruit paste.
-In Spain and especially in Portugal, arbutus unedo fruit is used to make a traditional alcoholic beverage (brandy): aguardente de medronho, or aguardente medronheira.
The ripe fruits are crushed and reduced to a pulp, and a little water is generally added (one volume of water to five volumes of fruit) to make the pulp more liquid.
Fermentation begins quite quickly naturally without the addition of yeast. The must is placed in a sealed container (wood, plastic, cement, or stainless steel) with a device that allows the gases produced to escape but prevents air from entering. After one to two months (depending on the temperature), fermentation stops and distillation can begin. Depending on the method, a fruit alcohol of between 40 and 50% alcohol is obtained.
If this distillation is carried out correctly (elimination of the head which contains methanol and the tail which contains long-chain alcohols with an unpleasant taste) we obtain a fragrant white alcohol which is not very toxic.
However, strawberry tree alcohol often contains methanol (neurotoxic) because the distiller does not always eliminate all of the first methanolic part of the distillate.
-Example of a preparation to compare aqueous extracts of strawberry tree and hawthorn fruits: wash the fruits, dry them (5 days at 50°C), pulverize them then mix for one hour with distilled water heated to 70°C, filter and freeze-dry.
The dry extracts were tested orally on laboratory animals at a dose of 300mg /kg of weight for 3 months. The extract of arbutus unedo fruit seems to be the most active at the metabolic level: reduction of fat mass, improvement of blood constants, in particular blood sugar, anti-inflammatory effect: therefore a good treatment to reduce obesity and counter the effects of type 2 diabetes.
Use to preserve food.
The antioxidant power of strawberry tree fruits allows the use of their extracts, rich in phenolic compounds, as functional ingredients in various pork preparations (frankfurter sausages, minced meat, pâté).
This plant extract is combined with other preservatives, the quantity of which is reduced (sodium ascorbate, potassium nitrite).
There is a protective antioxidant effect allowing the nutritional and organoleptic properties of these pork preparations to be preserved.
Strawberry tree fruit extract can also be used to stabilize the microbial flora of yogurts and thus increase their conservation without altering their taste.
LEAVES AND ROOTS OF THE STRAWBERRY TREE ARBUTUS UNEDO
The leaves and roots of the strawberry tree are rich in phenolic compounds, mainly flavonoids ,anti-inflammatory, antibiotic, diuretic and astringent tannins, as well as arbutin, which is used to lighten the skin.
They can therefore be used:
- in cases of diarrhea without fever, colic with watery diarrhea,
- in cases of simple urinary disorders: cystitis without emission of pus or blood, urethritis,
- to clean wounds or superficial burns in the absence of commercial antiseptic,
- to make a mouthwash or gargle: dental infection, canker sore, angina,
- as a complement to treatment for high blood pressure or type 2 diabetes,
- as a complement to treatment for stomach cancer, and also inflammatory gastritis and gastric infections with Helicobacter pylori (often responsible for gastric ulcers).
Dosage examples:
-Aqueous infusion: one tablespoon of leaf powder or leaves (fresh or dried) finely ground in 1/4 or 1/2 of very hot water depending on the desired concentration, let it infuse for a few minutes.
-External use as a gargle, mouthwash, on wounds or superficial burns.
-Oral use: one cup one to three times a day for diarrhea, colic, cystitis, urethritis or as a complement to antihypertensive treatment or type 2 diabetes or a weight-loss diet.
Stop this treatment in case of digestive disorders or constipation.
- Alcoholic tincture of strawberry tree leaves: 50 drops one to three times a day for the same indications.
Strawberry tree leaves can be found in pharmacies, herbalists or online in bulk, powder or capsules.
STRAWBERRY LEAVES AND ARBUTIN
There are many commercial preparations for lightening skin or removing dark spots on the skin containing arbutin extracted from plants (bearberry or strawberry tree) but most often containing chemically synthesized arbutin.
This natural or artificial arbutin is combined with other compounds that strengthen its action or limit skin inflammation (vitamin C, glutathione for example).
Follow the manufacturer’s instructions and immediately stop applying the product in the event of an inflammatory or allergic reaction: redness, burning sensation, appearance of small vesicles.
Do not use lightening products containing hydroquinone (they have been banned in France since 2001).
OTHER USES
STRAWBERRY HONEY
The strawberry tree blooms late (fall-winter) and this is a chance for the bees, which can thus harvest additional food to get through the winter at a time when nectar sources are scarce.
Strawberry tree honey can be abundant when the trees are numerous (e.g. in Morocco or Portugal), it is a slightly or very bitter amber honey, strong in taste and which keeps well.
It is slightly acidic, contains mineral elements (potassium, calcium, phosphorus and sodium) and anti-inflammatory phenolic compounds like the fruit and leaves but in smaller quantities.
It has antibiotic and antifungal properties.
Experiments on laboratory animals have shown that the addition of strawberry tree honey to food and the combination of honey + propolis can partially control type 2 diabetes and the liver and kidney functions of diabetic patients. This positive effect on the metabolism of diabetics is attributed to the presence of phenolic compounds. The combination of honey and propolis is the most effective.
Homogentisic acid is abundant in honey and considered a chemical marker of arbutus unedo honey.
STRAWBERRY TREE CULTIVATION
The strawberry tree is a tree that is very resistant to drought thanks to its deep roots (but as a corollary, it does not like to be transplanted), it prefers well-drained, slightly acidic soils but also grows in limestone regions. It is naturally present in regions with a Mediterranean climate but some varieties adapt to the oceanic climate on well-drained soil.
It can be grown in the ground (it resists moderate frost) and also in pots. It is a decorative tree whose fruits are « original », it can be used as evergreen hedges. Nurseries and garden centers offer different varieties. You must wait until spring, therefore the end of fruiting, to prune it.
OTHER SPECIES OF ARBUTUS
ARBUTUS ANDRACHNE
This species is native to the eastern regions of the Mediterranean (Greece, Turkey, Middle East), it is a tree that is generally larger than Arbutus unedo, its reddish or greenish trunk depending on the season exfoliates (peels) regularly. Its fruits are edible but can cause digestive problems when consumed too much fresh; they are often eaten dried like figs.
Arbutus andrachne (or Greek strawberry tree) contains phenolic substances with medicinal properties similar to those of Arbutus unedo
There are Arbutus unedo/Abrutus andrachne hybrids.
ARBUTUS MANZIESII
The Pacific madrone or madrona or madrono del pacifico is native to California and the Mexican Baja California.
It is a large tree with a slightly twisted trunk and bark that exfoliates like that of the Greek strawberry tree.
Its fruit is edible but very astringent (tannic); its wood is famous for making flooring or furniture.
There are a few other species of arbutus in the dry regions of North America.
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