Bearberry leaves (Uva Ursi, U.S.P.) are obtained from Arctostaphylos Uva-ursi, Sprengel (N.O. Ericaceae), a small, procumbent, evergreen shrub distributed over the greater part of the northern hemisphere. The dried leaves are dark green, obovate or spathulate, about 18 millimetres wide, rounded at the apex and tapering at the base into a short petiole. The texture is coriaceous; the margin entire; surface, glabrous, the upper being deeply impressed with a network of veins. They have no odour, but a very astringent, and somewhat bitter taste. On incineration, the drug yields about 3 per cent. of ash. The leaves of other plants have been mistaken for bearberry leaves, notably those of the cowberry, Vaccinium Vitis-idaea, and of the box, Buxus sempervirens. Bearberry leaves are readily distinguished by the characters already given, but the leaves of the cowberry may also be distinguished by the scattered brown dots on the under surface, and those of the box by their emarginate apex.
Constituents.—The chief constituents of bearberry leaves are tannin (6 to 7 per cent.), gallic acid, ellagic acid, arbutin, methyl arbutin, ursone, quercetin, and probably also myricetin. Arbutin, C12H16O7 + 1/2H2O, melting-point, 168°, is a crystalline glucoside yielding on hydrolysis dextrose and hydroquinone, a decomposition that takes place during its passage through the body, as hydroquinone is excreted in the urine. Ursone, C30H48O3 + 2H2O, crystallises in colourless, tasteless, odourless needles melting at 265°.
Action and Uses.—Bearberry leaves are diuretic and astringent. Their diuretic action is due to the glucoside arbutin, which is largely absorbed unchanged and is excreted by the kidneys. A proportion of arbutin is, however, hydrolysed, with formation of hydroquinone; this is also excreted in the urine, to which it gives a greenish-brown colour, darkening on standing, owing to oxidation. During its excretion, arbutin exercises an antiseptic effect on the urinary mucous membrane; bearberry leaves are therefore used in inflammatory diseases of the urinary tract, urethritis, cystitis, etc. They are usually administered in the form of infusion.
- Infusum Uvae Ursi, B.P.—INFUSION OF BEARBERRY.
- Bearberry leaves, bruised, 5; distilled water, boiling, 100. Infuse the drug in the water for fifteen minutes, in a covered vessel, and strain. Infusion of bearberry is a vehicle for diuretics and urinary antiseptics. It is important that the leaves be bruised, as a stronger infusion is thus obtained. Dose.—15 to 30 mils (1/2 to 1 fluid ounce).
- Infusum Uvae Ursi Concentratum, B.P.C.—CONCENTRATED INFUSION OF BEARBERRY.
- A product closely resembling infusion of bearberry is obtained by diluting 1 part of this preparation with 7 parts of distilled water. Dose.—2 to 4 mils (1 to 1 fluid drachm).
The British Pharmaceutical Codex, 1911, was published by direction of the Council of the Pharmaceutical Society of Great Britain.