Damiana. N. F. IV. Turnera.—"The leaves of Turnera diffusa Willdenow or of Turnera aphrodisiaca Ward (Fam. Turneraceae), without the presence of more than 10 per cent. of stems and other parts of the same plants or other foreign matter." N. F. There are 57 species of Turnera which are mostly indigenous to tropical America. The 2 species which yield damiana are small shrubs indigenous to Southern California, Mexico and the Antilles. These leaves are "obovate to lanceolate, from 10 to 25 mm. in length and from 4 to 10 mm. in width, shortly petiolate, obtuse or acute at the apex, and with a short, cuneate base; sharply two- to ten-toothed on each side; the veins ascending, generally strong, straight and simple, and running to the sinuses of the teeth, but sometimes branched and sending the branches into the teeth; the upper surface smooth and pale green, the lower glabrous or with a few hairs on the ribs (Turnera aphrodisiaca) or densely tomentose over the entire surface (Turnera diffusa). Intermixed with the leaves are frequently found some reddish twigs, the young tips and buds of which are grayish with appressed pubescence (Turnera aphrodisiaca) or white floccose (Turnera diffusa), also flower buds, yellowish flowers, and globose pods. Odor aromatic; taste characteristic, aromatic and resinous. The powdered drug is light yellowish-green and, when examined under the microscope, exhibits numerous rough simple hairs, up to 0.8 mm. in length and 0.03 mm. in width at the base, with a narrow lumen usually distinct at the base only and with heavy, mostly non-lignified walls, often curved near the base so that the major portion of the hair lies nearly parallel to the surface of the stem or leaf; fragments of the epidermis from the stems composed of somewhat rectangular .cells up to about 0.07 mm. in length and about one-half as broad, with square or somewhat pointed ends, with few broadly elliptical stomata about 0.03 mm. in length; sub-epidermal cells from the stem resembling those of the epidermis in shape but with lignified walls; tracheae, spiral, up to 0.02 mm. in width, with bordered pores up to about 0.035 mm. in width; tracheids from stem few; strongly lignified, thick-walled sclerenchyma cells or fibers few; lignified pith-parenchyma with large simple pores; fragments of epidermal cells and mesophyll of leaf; the former with somewhat wavy, vertical walls and associated with stomata up to 0.024 mm. in length; numerous crystals of calcium oxalate in rosette aggregates up to 0.03 mm. in diameter and occasionally in prisms; starch grains few, simple, up to 0.005 mm. in diameter. Damiana yields not more than 10 per cent. of ash." N. F.
Parsons (Arch. d. Pharm., 1881, p. 133) obtained 0.2 per cent. of a volatile oil; 8.06 of a soft resin, fixed oil and chlorophyll; 3.46 per cent. of tannin; 7.08 per cent. of a bitter principle; 6.39 per cent. of a hard brown resin; 10 per cent. of extractive; 13.5 per cent. of a gum; 6.15 per cent. of starch, etc.
The leaves of the composite plant Aplopappus discoideus DC. (Bigelovia Veneta Gray) were, formerly, also sold under the name of damiana.
Although damiana has achieved some repute in the treatment of sexual impotence, it is worthy of note that it is always given in conjunction with strychnine, phosphorus or some other stimulant; it is probably nothing more than a feeble tonic. Dose, one-half to one drachm (2-4 Gm.) of the leaves, either in the form of infusion or fluid-extract.