Real bearberry

The bearberry - also known as arctostaphylos or uva-ursi - is a shrub from the heather family (Ericaceae). The name "Arctostaphylos" (Greek) and "Uva ursi" (Latin) mean bearberry, which is said to be due to the fact that bears love the fruits of this shrub. Bearberry is native to the mountains of North America, but also grows in the higher regions of Europe and Asia.

Traditional and modern applications

Bearberry has long been used by peoples all over the world to treat urinary tract infections, inflammation, bladder and kidney stones, diabetes and venereal diseases. Traditional medicine uses creams and lotions to lighten the skin. Even today, skin whitening and the treatment of skin problems are among the most common uses of this plant (1, 2).

Native Americans added dried bearberry leaves to tobacco and other herbs to make a smoking mixture called "kinnikinnick".

Components

Only the dried leaves of bearberry are used medicinally. Commercial blends and teas often contain the whole plant, but this is an indication of poor product quality. The primary active ingredient is arbutin (5 - 12%), a complex sugar molecule. Enzymes in the digestive tract convert arbutin into hydroquinone, which is responsible for the medicinal effects. Standardized leaf extracts should contain 20% arbutin.

Bearberry leaves are also rich in tannins such as corilagin (10 to 20%), which can cleanse and contract tissues of the body. Other compounds include:

• Phenolic acids: gallic acid, P-coumaric acid and syringic acid
• Flavonoids: catechin, quercetin
• Enzymes: beta-glucosidase (arbutase)
• Triterpenes: ursolic acid, α-amyrin
• Minerals: iron, selenium, manganese
• Others: Allantoin, resin, wax, fatty acids

Fall is the best season to harvest the leaves and get the maximum amount of arbutin. Experts recommend using wild plants to get the best possible quality.

Mechanism of action

According to limited research, arbutin and its metabolite hydroquinone:

• Inhibit the growth of bacteria
• Prevent oxidative damage
• Relieve inflammation
• Protect the nerves

They also inhibit the enzyme tyrosinase, which is important for the formation of the skin pigment malanin (7). Although the majority of studies have focused on these two compounds, corilagin has also shown the above effects. Astringent and antibacterial properties Corilagin may contribute to bearberry's effects on urinary tract infections and infections (8, 9).

Health benefits of bearberry

Bearberry can relieve urinary tract infections

Every year, around 150 million people suffer from urinary tract infections. The resistance of bacteria that cause urinary tract infections, such as E. coli and E. faecalis, to antibiotics poses a major challenge to science, making alternative approaches such as bearberry important. In a clinical trial involving 57 women with urinary tract infections, bearberry prevented inflammation. After one month of treatment with 540 mg of the extract per day, the women were symptom-free for one year and reported no side effects (10). E. coli and other bacteria that can cause urinary tract infections did not survive in urine samples from patients who had taken bearberry extract or arbutin (100 to 1,000 mg) (11).This study also suggested that bearberry extract is more effective when taken at the first sign of infection.

Hydroquinone, the primary metabolite of arbutin, is more effective against bacteria in alkaline urine (pH of about 8). Sodium bicarbonate could make urine more alkaline and enhance the antibacterial actions of bearberry (12, 13). However, in a larger clinical trial involving 382 women, bearberry did not cure urinary tract infections. From the fourth day onwards, patients reported no difference in symptoms (14). A review of clinical trials and traditional use also questions the ability of bearberry to treat urinary tract infections. The authors recommended it for short-term prevention and emphasized the need for larger studies (2). In vitro studies on cells also suggest that the antibacterial effects of bearberry extract are also effective against common causes of urinary tract infections such as E. coli, S. saprophyticus, and E. faecalis (15, 16, 17). Corilagin and other tannins from bearberry leaves may reduce inflammation, tighten the walls of the urinary tract and help fight bacteria responsible for urinary tract infections (18, 19).

Bearberry may also help with other urinary tract problems

Kidney stones

In a study conducted with rats, scientists observed the ability of bearberry to dissolve kidney stones and cleanse the urinary tract. Once again, the scientists emphasized the role of an alkaline pH in these effects (21).

Elimination of excessive fluid retention

Increased urine output - also known as a diuretic effect - is one of the body's mechanisms for expelling bacteria from the urinary tract. Herbs and other substances with this effect can help with infections of the urinary tract and prevent the formation of kidney stones. In rats, bearberry was able to increase urine flow while maintaining electrolyte balance (21).

Bearberry could alleviate allergies and inflammation

In studies conducted on mice with allergies, a bearberry extract (4, 22, 23):

• Alleviate skin reactions
• Reduce inflammation and swelling
• Alleviate allergic reactions
• Support standard treatment with non-steroidal anti-inflammatory drugs and corticosteroids

A cream with bearberry extract (1 to 2%) shows similar results when applied to the animals' skin. Although it was not able to reduce swelling on its own, it was able to support the effects of a corticosteroid cream (24).

Bearberry can prevent microbial infections

Bacterial infections

The antibacterial effects of bearberry are not limited to infections of the urinary tract. In a cell study, an extract of bearberry reduced the growth of MRSA - a dangerous type of bacteria (S. aureus) that is resistant to common antibiotics. When this extract was combined with antibiotics, it increased their effect by a factor of 100 to 2,000 (25). The corilagin contained in bearberry leaves could inhibit the growth of Helicobacter pylori bacteria, which cause stomach ulcers (26).

Viral infections

According to cell studies, corilagin could prevent the spread of the HIV-1 virus by blocking its two essential enzymes - protease and reverse transcriptase. Corilagin was effective even against drug-resistant HIV strains, which could make it a promising adjunctive treatment (27, 28). However, further studies are needed to investigate its anti-HIV effects in the human body.

Bearberry could lower blood pressure

One of the main components of bearberry - corilagin - was able to lower high blood pressure in rats. It blocked the release of noradrenaline and relaxed the blood vessels (29, 30). Many drugs for high blood pressure, known as diuretics, work by stimulating the excretion of water via the urine. An extract of bearberry has shown the same effect in rats, although its effects on blood pressure have not yet been studied (21)

Bearberry could protect the liver

In animal studies, scientists have noted the potential of the corilagin contained in bearberry to protect the liver from the following threats (31, 32, 33):

• Parasite infestation
• Potentially toxic drugs
• Bleeding due to injuries
• Impaired flow of bile acid

However, further studies are needed to confirm these liver-protective effects in humans.

Possible applications of bearberry on the skin

Cosmetic products containing bearberry extract and its main constituents arbutin and hydroquinone have a long history of use for skin lightening and spot removal. A review of 30 clinical studies has declared arbutin to be an effective depigmenting, skin lightening agent. The same is true for its metabolite hydroquinone, but due to safety concerns, some experts recommend using these agents only for skin and nail products (34, 35).

In test tubes, bearberry leaves, arbutin and hydroquinone inhibited the production of melanin (37).

Side effects and precautions

In clinical studies, bearberry extracts and its primary ingredient arbutin have not caused any significant side effects. Long-term studies also suggest that these extracts are safe. However, there is one case report of a woman who developed retinal damage to her eye after three years of using bearberry (37). In the body, arbutin is converted to hydroquinone, which raises some safety concerns. In animal studies, this compound has been shown to increase the risk of kidney cancer. However, this observation was limited to a strain of older male rats and is unlikely to have implications for humans (38). Injected hydroquinone caused bone marrow damage in some experimental animals, but this was not the case with oral administration. A review of safety studies suggests that hydroquinone is safe for human consumption at the levels found in bearberry (39). Due to some evidence of long-term toxicity of hydroquinone, experts recommend limiting consumption of bearberry to 1 week at a time up to five times per year (12). Children under the age of 12 and pregnant women should avoid bearberry extracts.

Safety when used in the form of cosmetics

In clinical studies, patients reported no side effects after using a cream containing 2 to 4% hydroquinone for up to three months. Skin toxicity studies also indicate the safety of such products, although one review recommends limiting use to hair coloring products and nail products.

Interactions with medications

Bearberry extracts can inhibit CYP enzymes, which metabolize various drugs and chemicals in the body. The following drugs may interact with bearberry extracts (40, 41):

• Statins (drugs to lower cholesterol levels)
• Selective serotonin reuptake inhibitors (antidepressants)
• Azoles (antifungal drugs)
• Some antibiotics and antivirals

Drugs and medicinal plants that increase urine excretion (diuretics) - which include bearberry extracts - can provoke side effects when used with lithium, which is used to treat depression. Due to its dehydrating properties, bearberry could enhance the effect of medication for high blood pressure (42).

Available dosage forms of bearberry

Capsules and dry powdered extracts are the most common forms of bearberry supplements. Some of these products are standardized to the amount of the active ingredient arbutin.

Bearberry is also available in the following forms:

• Loose tea (truffled leaves)
• tea bags
• Liquid extracts

Bearberry is also popular in the field of cosmetics. Various skin-lightening creams and liquid preparations contain bearberry leaf extracts and its main constituents arbutin and hydroquinone.

Dosage

In clinical dosages, the dosages ranged from 400 to 1,000 mg of arbutin, which corresponds to 2 to 5 grams of a standardized bearberry extract (20% arbutin).

For other forms, experts recommend the following dosages:

• Tea: 3 grams of dried leaves infused with 150 ml of water, three to four times a day for one week.
• Powdered leaves: Up to 1,750 mg per day divided into 2 to 3 single doses
• Liquid extract: 1.5 to 4 ml per day (maximum 8 ml per day)

Combinations with other medicinal herbs

In a successful clinical trial for the prevention of urinary tract infections, women took a supplement containing bearberry extract and nettle root extract (43). Users often combine bearberry with other medicinal herbs that stimulate urination, reduce inflammation and help fight urinary tract infections. Corn stigmas, nettle root and parsley leaves, horsetail and marshmallow root are often included in such mixtures. However, there are few or no studies that have tested the safety and efficacy of these mixtures. Cranberry juice or extract is another popular natural remedy for urinary tract infections, but it should not be combined with bearberry as it acidifies the urine, potentially reducing the antibacterial effects of bearberry (44).

References

1. https://www.ema.europa.eu/en/documents/herbal-report/draft-assessment-report-arctostaphylos-uva-ursi-l-spreng-folium_en.pdf
2. https://www.ncbi.nlm.nih.gov/pubmed/18950249
3. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4649267/
4. https://www.ncbi.nlm.nih.gov/pubmed/1875280
5. https://www.ncbi.nlm.nih.gov/pubmed/18996230
6. https://www.ncbi.nlm.nih.gov/pubmed/30503994
7. https://www.ncbi.nlm.nih.gov/pubmed/24189417
8. https://www.ncbi.nlm.nih.gov/pubmed/29324311
9. https://www.sciencedirect.com/science/article/pii/S0014299910001949
10. https://www.sciencedirect.com/science/article/pii/S0011393X05802048
11. https://www.ncbi.nlm.nih.gov/pubmed/240095
12. https://link.springer.com/article/10.1007/s00345-002-0293-0
13. https://www.thieme-connect.com/products/ejournals/abstract/10.1055/s-0028-1099743
14. https://www.ncbi.nlm.nih.gov/pubmed/3068550
15. https://www.ncbi.nlm.nih.gov/pubmed/28245081
16. http://eemb.ut.ee/humb/refH/Turi_1997_1.pdf
17. https://www.ema.europa.eu/en/documents/herbal-report/draft-assessment-report-arctostaphylos-uva-ursi-l-spreng-folium_en.pdf
18. https://www.ncbi.nlm.nih.gov/pubmed/29324311
19. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3655894/
20. https://www.ncbi.nlm.nih.gov/pubmed/7860196
21. https://www.ncbi.nlm.nih.gov/pubmed/10353162
22. https://www.ncbi.nlm.nih.gov/pubmed/2355310
23. https://www.ncbi.nlm.nih.gov/pubmed/1693958
24. https://www.ncbi.nlm.nih.gov/pubmed/1469616
25. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC90804/
26. https://www.sciencedirect.com/science/article/pii/S0378874113001414
27. https://www.jstage.jst.go.jp/article/bpb1993/23/9/23_9_1072/_article
28. https://www.ncbi.nlm.nih.gov/pubmed/12742578
29. https://www.ncbi.nlm.nih.gov/pubmed/8748933
30. https://tmu.pure.elsevier.com/en/publications/antihypertensive-activity-of-corilagin-and-chebulinic-acid-tannin
31. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6327405/
32. https://www.ncbi.nlm.nih.gov/pubmed/26946098
33. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5811621/
34. https://www.ncbi.nlm.nih.gov/pubmed/8654129
35. https://www.ncbi.nlm.nih.gov/pubmed/2890657
36. https://www.ncbi.nlm.nih.gov/pubmed/1403661
37. https://www.ncbi.nlm.nih.gov/pubmed/15183807
38. https://www.ncbi.nlm.nih.gov/pubmed/17177740
39. https://www.ncbi.nlm.nih.gov/pubmed/18027166
40. https://www.ncbi.nlm.nih.gov/pubmed/18066112
41. https://www.ncbi.nlm.nih.gov/pubmed/18473749
42. https://www.ncbi.nlm.nih.gov/pubmed/8521679
43. https://www.sciencedirect.com/science/article/pii/S0011393X05802048
44. https://www.goldjournal.net/article/S0090-4295(00)01100-6/fulltext