Arctostaphylos uva ursi is a small perennial evergreen shrub, native to Europe and to the northern US, known by other names like bearberry, upland or mountain cranberry, mealberry, whortleberry and others. Traditionally the herb has been used for nephritis, kidney stones and chronic cystitis. The principal active ingredients of the leaves are glycosides like arbutin and methylarbutin, tannins, flavonoids like quercetin, allantoin, gallic and elagic acids, volatile oils and resins like urvone. And the principal use of the herb is as an antibiotic, antiseptic, diuretic and pain reliever of the urinary tract, and secondarily as a liver, kidney and pancreatic tonic.
As in many other cases, pharmacological research has been focused on what is considered the main active ingredient, that is arbutin. But the activity of arbutin is less than the total plant. This is no doubt partly because when arbutin is given by itself, intestinal bacteria break down much of the arbutin before it is converted to hydroquinone and absorbed. When the whole plant extract is taken, components of the plant prevent the breakdown of arbutin, and a greater amount of hydroquinone is now absorbed, turning the urine an envious green if harmless color.
Thus as it is frequently the case, the crude plant extract is more useful than the single most active ingredient. In the case of Uva ursi, this is even more strikingly true. For the activity of the herb as an antibiotic of the urinary tract depends on urine being alkaline. As it happens, many of the other ingredients of the herb tend to make the urine more alkaline.
Caution. The toxicity of the herb is linked to the conversion of arbutin to hydroquinone. The latter has been found toxic at one gram, producing tinnitus, nausea, vomiting, shortness of breath, a sense of suffocation, cyanosis, convulsions, delirium and collapse. It is contra-indicated for pregnant women; in cases of acute cystitis; and persons with acid urine. The urine may be turned alkaline by taking a heaped teaspoon of bicarbonate of soda.