In traditional folk medicine, barberry soothes sore throats, treats diarrhea or constipation, and eases inflammation and infection of the urinary, gastrointestinal, and respiratory tracts. It may reduce the discomfort of arthritis and rheumatism, soothe psoriasis, and treat chronic yeast infections. These uses reflect barberry's reputation as an herbal antibiotic.

Sought after as an alternative to goldenseal (a once-endangered botanical regarded as "king" of herbal antibiotics by some individuals), barberry and other herbs with similar constituents (e.g., berberine) and actions are termed mucous membrane tonics and adaptogens by herbalists. Mucous membrane tonics regulate the flow of mucus; they may increase or decrease mucus secretion. Adaptogens also allow immune factors already present within the body to stimulate antibacterial responses during illness.

The study of barberry's isoquinoline alkaloid constituents has overshadowed study of the plant as a whole. These constituents are potentially therapeutic, with bactericidal, smooth muscle, and cardiovascular effects.

Barberry was used in ancient Egypt to prevent the plague, during the middle ages in Europe as a purgative and antiseptic, and by Native Americans as tea to stimulate the appetite. It has other uses as well; the yellow color of the root and inner bark provide a semi-colorfast clothing dye, and the berries can be made into jam or sugared for cake decorations.

Deciduous shrub grows to nine feet. Branches, gray, bear thorns. Leaves alternate or in rosette formation, can be various colors, spiny teeth, four to five leaves per branch. Flowers, bright yellow, in 2¹/2 inch racemes, bloom April to June. The berries are red and grow in drooping bunches. Inner bark is yellow.

The bark of the stem and root, and the root itself, are used medicinally. Traditionally, the berries were also used as a tonic in tea, but they do not contain isoquinoline alkaloids and are more closely associated with culinary use. Barberry grows in the northeastern United States, particularly in New England, and is native to Europe.

• Roots
• Berry
• Root bark
• Stem bark

Isoquinoline alkaloids berberine, berbamine, oxyacanthine, jatrorrhizine, columbamine, palmatine, magnoflorine; also, resin, tannins

Crude bark for tea or powdered in capsules; aqueous alcohol or alcohol extracts available as 1:5 tinctures or standardized fluid extracts (standardized to 8% to 12% isoquinoline alkaloids); ointment

• Traditional: Berry as tea, diuretic, expectorant, laxative, appetite stimulant; root bark and bark as tea, anti-inflammatory, diaphoretic, astringent, antiseptic, laxative, bitter tonic, alterative (blood purifier), cholagogue (liver stimulant that promotes bile excretion)
• Conditions: chronic diarrhea, dysentery, indigestion, eye ailments, mouth sores, jaundice, hepatitis, fever, hemorrhage, arthritis, rheumatism, low back pain, stomach bacterial infections, H. pylori 
• Clinical applications (listed as "unapproved" in German Commission E monograph): Inflammation/infection of the kidneys and urinary, bronchial, and gastrointestinal tracts; liver, spleen, and circulatory disorders; spasms; and chronic candidiasis

Herbalists provide much of the information available on the usage and effects of whole barberry rootbark and bark preparations. While these sources often corroborate empirical results of barberry use, scientific study tends to focus on determining the scope and application of the bactericidal activity of the isoquinoline alkaloid constituents. At least one study demonstrated superior anti-inflammatory actions of whole barberry extract, compared to single constituents. By using tissue or bacterial cultures and single alkaloid preparations, researchers have determined antimicrobial, bactericidal, anti-inflammatory, immune-stimulant, hypotensive, antifibrillatory, antiarrhythmic, sedative, anticonvulsant and smooth muscle effects.

Berberine has in vitro antibacterial activity. Actions against Staphylococcus spp., Streptomyces spp., Chlamydia spp., Corynebacterium diphtheria, Escherichia coli, Salmonella typhi, Vibrio cholerae, Diplococcus pneumoniae, Pseudomonas spp., Shigella dysenteriae, Entamoeba histolytica, Trichomonas vaginalis, Neisseria gonorrhoeae, N. meningitidis, Treponema pallidum, Giardia lamblia, Leishmania donovani, and Candida albicans may be due to adhesion blockage of the streptococci to host cells through the depletion of lipoteichoic acid and fibronectin. In other studies berberine raised blood flow to the spleen; reduced fever, possibly by altering interferon response to microorganisms; stimulated bile secretion; altered bilirubin levels; inhibited brain tumor cells in rats; and was superior to sulfacetamide against Chlamydia trachomatis.

In vitro studies demonstrate that oxyacanthine dilates blood vessels, modulates adrenaline, and is bactericidal to Bacillus subtilis, Colpidium colpoda. Palmatine is antiarrhythmic, adrenocorticotrophic, analgesic, and bactericidal. Jatrorrhizine is sedating, hypotensive, and fungicidal. In animal studies, one experiment showed a berbamine-induced immune response in mice with influenza.

These actions have not been scientifically demonstrated to occur in the human body. Berberine absorption in the small intestine is poor, and large doses obtained through excess intake of berberine-containing plant preparations cause negative side effects on the stomach and small intestines. However, because it is excreted through the urine, it may have antibiotic actions specific to that area of the body. This remains to be proven, but concurs with traditional use.

For throat, urinary, gastrointestinal, respiratory inflammation or infection, including chronic candidiasis, any of the following can be taken for five to seven days.

• Tea: 2 to 4 g steeped dried root tid
• Tincture (1:5): 3 to 6 ml tid
• Dry extracts: 250 to 500 mg tid

For skin disorders: 10% extract of barberry in ointment, applied topically tid

American Herbal Products Association safety rating: 2b. Safe with appropriate use, but do not use during pregnancy. Due to a lack of scientific documentation of barberry's purported therapeutic uses, the German Commission E monograph lists barberry as an unapproved herb.

Barberry root and root bark preparations have not caused any of the toxic effects noted with excessive or lethal doses of berberine. (At doses higher than 0.5 g, berberine causes lethargy, nose bleeds, difficulty breathing, skin and eye irritation, kidney irritation, nausea, vomiting, and diarrhea. Small doses stimulate respiratory system; large doses lead to respiratory paralysis. Lethal doses cause hemorrhagic nephritis.)

Over-consumption of berberine-containing plant medicines may irritate mucous membranes, particularly in the stomach. Do not use during pregnancy.

No clinically significant interactions between barberry and conventional medications are known to have been reported in the literature to date, including the German Commission E monograph (Blumenthal 1998).

In the United States, barberry is a dietary supplement; in Germany the Commission E does not approve therapeutic use due to lack of scientific documentation of effects.

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