Use of Arctostaphylos uva-ursi Extracts for the Treatment of Urinary Tract Infections

Abstract

Extracts of the low-lying shrub Arctostaphylos uva-ursi, which is commonly referred to as “bearberry” or simply as Uva ursi, have been widely promoted and frequently used as an herbal treatment for urinary tract infections. These extracts contain a wide range of organic chemicals such as arbutin (4-hydroxyphenyl-β-D-glucopyranoside), polyphenolic compounds, and flavonoids. Arctostaphylos uva-ursi extracts have been shown to inhibit the growth of uropathogenic Gram-negative bacteria. These include Escherichia coli, Proteus mirabilis, Pseudomonas aeruginosa, and Klebsiella pneumoniae. They also inhibit Gram-positive bacteria such as Staphylococcus aureus and Staphylococcus saprophyticus, and the pathogenic yeast Candida albicans. This review article summarizes the experimental work on the inhibition of microbial growth by Uva ursi extracts and their components. It describes the complementary studies on the effects of these extracts on two key virulence factors, the enzyme urease and the ability of the microbes to form biofilms. The article also reviews the antioxidant and anti-inflammatory properties of these extracts and their effects on other host functions. The preliminary animal and human studies with Arctostaphylos uva-ursi extracts are summarized, as are the human clinical trials that have been completed so far. These studies have shown that these extracts are relatively safe, although the key component arbutin can be metabolized to form the more toxic compound hydroquinone. Although the laboratory data indicate that Uva ursi preparations can effectively inhibit urinary tract pathogens and so may represent an alternative to traditional antibiotics, the clinical studies are far more limited and currently insufficient to justify their widespread medical use. Further areas of research might include the use of extracts from plants with low arbutin contents or the combination of Arctostaphylos uva-ursi extracts with those from other plants.