Source Etc

The common bearberry, Arctostaphylos Uva-ursi, Sprengel (N.O. Ericaceœ), is a small procumbent ever-green shrub distributed throughout central and northern Europe and North America. It is indigenous to Great Britain, but is confined to Scotland, the north of England, and Ireland. The plant sends out branching stems that take root, and so forms small clumps. The drug was probably in use long ago in this country but was first introduced into the London Pharmacopoeia in 1788.

Description

Bearberry leaves are small, shining, coriaceous leaves, seldom measuring as much as 25 mm. in length by 12 mm. in breadth. The upper surface is dark green or yellowish green, the under surface paler. They are spathulate or obovate, the lamina being rounded at the apex, but tapering gradually towards the base to a short petiole. They are more or less rigid, and, when quite dry, brittle. The margin is entire, slightly revolute, and in young leaves ciliate with short hairs, but these are scarcely discernible in the drug. The veins and veinlets, are depressed on the upper surface, which thus assumes a chequered or wrinkled appearance; the greyish green under surface is reticulately marked with somewhat darker veins, which are often slightly raised, but it does not show raised brown points when examined with a lens. The leaves have no marked odour, but are strongly astringent and somewhat bitter. The student should observe

(a) The spathulate outline, entire margin, and rounded apex,

(b) The veinlets depressed on the upper surface,

(c) The absence of brown points on the under surface; and should compare the leaves with (i) Buchu leaves, which have a toothed margin, (ii) The substitutes mentioned below.

Constituents

Bearberry leaves contain both tannin and gallic acid; an infusion of the leaves accordingly gives a bluish black precipitate with ferric salts. They also contain arbutin, methyl - arbutin, ursone, quercetin, and possibly myricetin.

Arbutin, C12H1607,H10, crystallises in long white bitter needles melting at 168° and easily soluble in boiling water and in alcohol; when hydrolysed with dilute sulphuric acid (or with emulsin) it yields dextrose and hydroquinone. A similar decomposition takes place when arbutin is administered by the mouth, both arbutin and hydroquinone being excreted by the urine; in fact, the activity of bearberry leaves is said to be partly due to the stimulant and antiseptic properties of the latter substance. Arbutin has also been detected in several other Ericaceous plants.

Fig. 28.   Bearberry. Reduced to about one fourth natural size. (Maisch.)

Fig. 28. - Bearberry. Reduced to about one-fourth natural size. (Maisch).

Constituents 52Constituents 53Constituents 54Constituents 55Fig. 29.   Bearberry leaves. Natural size.

Fig. 29. - Bearberry leaves. Natural size.

Ursone, C30H48O3,2H1O, has been obtained in tasteless, colourless, odourless crystals.

Quercetin, C15H10O7,2H1O, is a yellow crystalline body which occurs in the fruits of Rhamnus infectoria, Linne, etc, and is also obtained when quercitrin, one of the constituents of quercitron bark (Quercus discolor, Aiton), is hydro-lysed by boiling with, dilute mineral acids.

Ericolin, an ill-defined amorphous substance said to occur in this and other Ericaceous plants, is probably a mixture.

Substitutes

Bearberry leaves are seldom adulterated; the leaves of the box (Buxus sempervirens, Linne) and of the cowberry (Vaccinium Vitis-idœa, Linne) are reported to have been used for that purpose, but are easily distinguished, as the former are emarginate at the apex, and the latter have brown dots scattered over the under surface of the leaf.

Uses

Bearberry leaves are used as a stimulant, diuretic, and antiseptic in diseases of the urino-genital tract; they resemble buchu in their action, but are more astringent.