Herbs containing potent cardioactive glycosides

During this century, the drugs utilized most frequently by physicians for the treatment of CHF have been obtained from digitalis—the dried leaves of Digitalis purpurea L. or the dried leaves of D. lanata Erh. These members of the plant family Scrophulariaceae yield several potent cardiac glycosides, especially digitoxin, which is derived from both, and digoxin, which is prepared only from D. lanata. These two glycosides now account

for all of the digitalis prescriptions normally dispensed in the United States. However, a standardized D. purpurea leaf preparation, powdered digitalis, is official in the USP and is still employed, along with similar products, in other countries.

Numerous other plants contain cardioactive glycosides with steroidal structures and physiological functions similar to those of digitalis. Some of these have been used from time to time in the treatment of CHF, but none presents any special advantage over digitalis. Therefore, only the names

and botanical origins of some of the more common ones are listed here 2 : • adonis— Adonis vernalis L., family Ranunculaceae;

• apocynum or Black Indian hemp— Apocynum cannabinum L. or A. androsaemifolium L., family Ranunculaceae; • black hellebore— Helleborus niger L., family Ranunculaceae; • convallaria or lily of the valley— Convallaria majalis L., family

Convallariaceae; • oleander— Nerium oleander L., family Apocynaceae; • squill— Urginea maritima (L.) Bak., family Liliaceae; and • strophanthus— Strophanthus kombé Oliv. or S. hispidus DC., family

Apocynaceae. CHF is a serious disturbance of multiple origins that requires prompt,

accurate diagnosis and careful treatment. The cardiac glycosides are extremely potent drugs, the dosage of which must be carefully adjusted to the needs of the individual patient. In the case of phytomedicines containing them, this is possible only with the standardized powdered digitalis, a product not readily available in the United States. Because nonprofessional

Chapter six: Cardiovascular system problems

93 diagnosis and treatment of seriously involved CHF patients are not in the

best interest of the patients, the names and sources of the herbal products containing cardioactive glycosides employed to treat it are listed here only for the record, and no further details concerning their use are provided.

Other herbs for treating CHF Hawthorn

In Europe, an extract of the dried leaves and blossoms of hawthorn is widely used to treat the early stages of congestive heart failure and minor arrhyth-

mias for which cardioactive glycosides are not yet indicated. In some cases, it is used as adjunct therapy in combination with cardioactive glycosides.

This herb consists of the leaves with flowers or fruits of Crataegus laevi- gata (Poir.) DC. or C. monogyna Jacq. of the family Rosaceae. The principal activity of these plant materials is attributed to their content of oligomeric procyanidins derived from catechin or epicatechin. Additional effects are provided by various flavonoids, including quercetin, rutin, hyperoside, vitexin, and vitexin rhamnoside. 3

In chronic heart failure, hawthorn is reported not only to improve the pumping capacity of the heart but also to reduce patients’ susceptibility to cardiac angina. In contrast to the cardioactive glycosides, which mainly act on the cardiac muscle, hawthorn acts both myocardially and peripher- ally to reduce vascular resistance. The vasodilating and positive inotropic effects of hawthorn extracts have been attributed to the oligomeric procyanidins and flavonoid constituents. 4,5

However, accurate evaluation of the utility of hawthorn is difficult because most of the pharmacological and clinical studies of it have been conducted utilizing standardized extracts prepared by methods of which

the details are proprietary information. 6 Still, it appears that the herb causes

a direct dilation of the smooth muscles of the coronary vessels, thereby lowering their resistance and increasing blood flow. The tendency toward angina is thus reduced. It is, however, not useful for acute attacks because its effects develop quite slowly following continued consumption.

In a randomized controlled study testing the effects of daily doses of

a commercial hawthorn extract, the test group of seventy-eight patients with NYHA FC-II congestive heart failure made significant gains in their stamina and endurance as measured by a stationary bicycle. Test patients also had lower blood pressure and heart rates while exercising and felt less

fatigue and shortness of breath than controls. 7 Research studies presented at the Crataegus Symposium in Cologne, Germany, in 1994 reported pharmacological investigations demonstrating that hawthorn extract improves the perfusion of blood to all areas of the peripheral vascular system. Four independent clinical, placebo-controlled studies showed a connection

94 Tyler's herbs of choice: The therapeutic use of phytomedicinals between the length of treatment and therapeutic efficacy. Physical func-

tioning capacity improved at daily doses of extract over a period of at least four weeks and, to an even greater degree, after eight weeks. It was also shown that the hawthorn extract was equivalent to the ACE inhibitor captopril in terms of influence on stress tolerance. 8

The incidence of side effects in the clinical use of hawthorn is very low. The toxicity of the plant has been estimated at an LD 50 of 4,000 mg/kg and can be considered quite safe if one compares this value with caffeine, which has an LD 50 of 200 mg/kg. 9 A hydroalcoholic hawthorn extract standardized to 18.75 percent oligomeric procyanidins has been investigated in single- and repeat-dose toxicity studies. At one hundred times the recommended human dose, there was no target organ toxicity and a battery of standard mutagenic and clastogenic tests was negative. 10

German Commission E has approved the use of hawthorn for cardiac insufficiency corresponding to NYHA FC-I and FC-II for patients with a feeling of pressure and tightness in the cardiac region, as well as for the aging heart not yet requiring cardiotonic glycosides. The mini- mal daily dosage is established on the basis of flavone (5 mg) calculated as hyperoside, total flavonoids determined as total phenols (10 mg), or

oligomeric procyanidins calculated as epicatechin (5 mg). 11 Because standardized extracts providing these dosage levels are not available in the United States and the wisdom of self-treating any abnormal heart condi- tion is highly questionable, the use of such a remedy—even one as devoid of side effects as this—cannot be recommended at this time. In the future, however, because of its demonstrated efficacy and low incidence of side effects, hawthorn has considerable potential as an important drug for patients with the milder symptoms of congestive heart failure, provided standardized preparations become available and they take the drug only after consultation with their physicians.

Herbs containing potent cardioactive glycosides