Digitalis

Digitalis purpurea L. – Foxglove
Scrophulariaceae – Figwort family

Species used in medicine include: foxglove Digitalis purpurea L. and woolly foxglove Digitalis lanata Ehrh., and both provide the raw material in the form of rosette leaves, harvested in the first year of vegetation, and the sessile leaves, harvested in the second year.

Foxglove – appearance and origin:

The foxglove is found in Europe and West Asia and is grown in North America; the woolly foxglove originates from Southeast Europe and is grown in Poland and other Central European countries. Both species are biennial. They require fertile soil with plenty of humus, with neutral or slightly acidic pH. The stem is tall 40-160 cm, straight. The leaves are basal and ovate. The flowers are large, hanging, clustered on one side. They bloom in June and July. The fruit is an ovate capsule. The plants are highly poisonous!

Foxglove – effects and use:

The foxglove leaf (Digitalis purpureae folium) contains 0,1-0,4% of cardenolides. From among 30 isolated cardiac glycosides, the most important belong to 3 groups:

A – digitoxigenin derivatives (purpurea glycoside A and digitoxin called digitalin)

B – gitoxigenin derivatives (purpurea glycoside B and gitoxin)

E – gitaloxigenin derivatives (purpurea glycoside E and gitaloxin).

The foxglove leaves also contain digitanol glycosides, spirostane-type steroidal saponosides, flavonoids, phenolic acids and anthracompounds.

The wolly foxglove leaf (Digitalis lanatae folium) contains 0,4-1% cardenolides. About 60% of them is known and they belong mainly to 5 groups:

A – digitoxigenin derivatives (lanatoside A and its heteroside derivatives acetyldigitoxin and digitoxin)

B – gitoxigenin derivatives (lanatoside B, acetylgitoxin and gitoxin)

B – digoxigenin derivatives (lanatoside C, acetyldigoxin and digoxin)

D – diginatigenin derivatives (lanatoside D and acetyldiginatin)

E – gitaloxigenin derivatives (lanatoside E, acetylgitaloxin, digitanol glycosides, spirostan-type steroidal saponins, flavonoids and anthracompounds).

The currently used substances are: digoxin isolated from woolly foxglove leaves and metildigoxin (its methyl derivative), sometimes acetyldigitoxin isolated from common foxglove leaves. The synergistic activity of digitoxin and paclitaxel was observed in vitro, as they inhibit breast cancer cell proliferation more than paclitaxel alone.

Foxglove – effects and use:

– For the treatment of heart failure and supraventricular tachycardia, mainly atrial fibrillation.
The cardiac glycosides in the common foxglove, woolly foxglove and other Digitalis species have a multidirection effect on the heart, increasing the contractility of heart fibers. They increase the contraction force, extend the relaxation phase, reduce the heart rate, increase the heart muscle tension during contraction and inhibit stimuli conduction during relaxation. The increase in the force and amplitude of contraction and cardiac output causes the heart to work more efficiently. The flow of blood through kidneys is increased which improves diuresis and eliminated edema.

– Highly toxic!
Cardiac glycosides are highly toxic as medicine, mainly due to a small difference between a therapeutic and toxic dose, as well as possible cumulation.

An excessive dose may cause poisoning. The most common symptoms are decreased appetite, nausea, vomiting and diarrhea; also headaches, drowsiness, fatigue. The most dangerous is cardiac arrhythmia. Currently used products contain pure, single glycosides which are standardised using the newest analytical methods, therefore they are easy to dose.