FOXGLOVE

Family: Sorophulariaceae, Digitalis species

Source: Simon, J.E., A.F. Chadwick and L.E. Craker. 1984. Herbs: An Indexed Bibliography. 1971-1980. The Scientific Literature on Selected Herbs, and Aromatic and Medicinal Plants of the Temperate Zone. Archon Books, 770 pp., Hamden, CT.

Foxglove is the common name for plants of the Digitalis species, primarily represented by common foxglove, Digitalis purpurea L., and Grecian foxglove, Digitalis lanata J. F. Ehrh. These biennial or perennial plants, native to the Mediterranean region, reach heights of 1.2 to 2 meters. The plants have lanoeolate to ovate leaves and showy bell-shaped flowers in racemes. Foxglove, almost always produced under commercial contract, has traditionally been grown in Germany, England, India, and several eastern European countries.

The reported life zone for common foxglove is 6 to 21 degrees centigrade with an annual precipitation of 0.3 to 2.1 meters and a soil pH of 4.5 to 8.3 (4.1-31). The hardy, easy to grow plant flourishes in well-drained loam soil. Because of the small seed size and nonuniform germination of the typical heterogenous seed lots, plants are usually transplanted into the field to obtain the desired plant density. Leaves are harvested late in the first fall or in the following spring. Plants are dried in the shade or with artificial heat. Exposure to sunlight or moisture decreases the medicinal value of the leaves.

There are many natural, secondary, and other derived compounds from Digitalis species. The important cardenolides or cardiac glycosides include digitoxin, digoxin, gitoxin, from the lanatosides A, B, and C, and from purpurea glycoside A and B. The important saponins include digitonin, tigonin and gitonin. Additional medicinally useful steroids and cortical hormones can be made from the plant steroids. The glycoside content of tissue varies with the individual plant, the stage of development, the growth environment, and the time and method of harvest. Comfrey leaves have been reported to be used as an adulterant (11.1-50).

There are several varieties of ornamental foxglove available, differing in size and flower color. The primary value of foxglove, however, is as a source of the medicinally important glycosides found in the plant. Digitalis, a cardiovascular drug extracted from the leaves, is the most effective drug available for heart failure caused by hypertension or arteriosclerosis (11.1-96). It is also used medicinally as a heart regulator, a diuretic, and an expectorant. Digoxin and lanatoside C from foxglove are effective in the correction of arrhythmias (11.1-95). Folk remedies use foxglove as a cardiac tonic and in the treatment of circulatory failures (11.1-154). The cardenolides slow and strengthen the heart beat.

Digitalis is poisonous, and symptoms include vomiting, headache, irregular heartbeat, and convulsions (11.1-96). Overdoses can be fatal.

Several wild strains and cultivated varieties of foxglove exist and are collected or produced for their ornamental and medicinal values.

[Note: References listed above in parentheses can be found in full in the original reference].

Last modified 6-Dec-1997