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Yam Plant

Yam Plant

Botanical Description & Habitat

Dioscorea spp

Family
Dioscroeaceae

Common Names
Mexican yam

Habitat
Mainly in Mexico and India

Medicinal Parts
Tubers

Historical Properties & Uses

Wild yam root has been used for hundreds of years to treat rheumatism and arthritis-like ailments. The discovery of steroidal glycosides (diosgenin) in the root validated this ancient practice.

Method of Action

Yams are the Best Source of Steroidal Precursors
Most species of yams contain large amounts of plant steroids, primarily diosgenin, a saponin precursor in the synthesis of progesterone. Without the yams, the industrial complex would not be able to meet the world wide demand for synthetic corticosteroids. But with them, scientists can derive animal or human steroids in a fairly straight forward multi-step process.

Wild yams are really the only good source of plant steroids for such purposes. Agave and Yucca are two other sources, neither of which equals wild yam. Diosgenin provides about 50% of the raw material for steroid synthesis. Stigmasterol, from soybeans and other herbs, comes about as close as any other plant sterol to being useful in steroid synthesis, but yields what is better called a semi-synthesis.

In steroid synthesis, the carbohydrate moiety is usually split off from the 3-OH group during the isolation. Rings E and F of diosgenin can then be degraded to yield 20-oxo-5,16-pregna-dien-3beta-yl acetate (PDA), which is the material for the preparation of most types of steroid hormones, formed after a lengthy series of ring transformations. This is mentioned simply to demonstrate there is not an equivalency between diosgenin and human steroids. If yam has steroidal effects on the body it is not because it contains steroidal hormones, but because the steroidal precursors have similar effects by an as yet unknown mechanism. The body does not recognize them or mistake them for its own hormones.

Yams have Anti-inflammatory and Anti-arthritic Action
Research has shown yam, yam extract and/or diosgenin possess good to excellent anti-inflammatory action.

In one series of studies, yam was found to induced a short-lived decrease in blood pressure and an increase in coronary flow when injected i.v. into rabbits. Also in rabbits, the saponins, fed orally, of yam prevented large increases in blood cholesterol levels.

The good therapeutic effect of dioscorea saponins on patients with atherosclerosis combined with hypertension was confirmed in clinical practice.

Yams and DHEA
Another important use for wild yam root has surfaced in recent years, involving the presence of dehydroepiandrosterone, or DHEA, a substance apparently, unlike the sex hormone precursors, is identical to a hormone produced in the adrenal glands of mammals.

DHEA is the most abundant steroid circulating in the plasma of normal human adults. The purpose of this substance has been a mystery. Now, researchers have discovered an inverse relationship between blood levels of DHEA and the risk of developing obesity, atherosclerosis and cardiovascular disease.

Furthermore, plasma levels of DHEA appear to be linked to all disease-related causes of premature death, not just cardiovascular disease. The relationship appears to be one of cause and effect. Lower DHEA levels actually cause premature death. Plasma levels of DHEA drop approximately 6.5ug/dl for each year of life. Men in their 70's have DHEA levels 10-20% lower than men in their 20's. And men with higher levels live longer.

Animal studies have shown DHEA administration delayed aging, inhibited obesity and lowered cholesterol levels in the blood. The implication is clear; though DHEA levels might naturally decrease with age, supplementation can keep them high enough to delay the effects of aging.

The British Herbal Pharmacopoeia recognizes wild yam root as a spasmolytic, mild diaphoretic, anti-inflammatory, anti-rheumatic, and cholagogue, for use in the treatment of intestinal colic, diverticulitis, rheumatoid arthritis, muscular rheumatism, cramps, intermittent claudication, cholecystitis, dysmenorrhea, and ovarian and uterine pain.

Bilious colic and rheumatoid arthritis are specific indications for the use of yam. It is combined with acorus, camomile, or ginger root to treat intestinal colic; with cramp bark and black cohosh in rheumatoid arthritis; with elder flowers and marshmallow for appendicitis and diverticulitis.

Drug Interactions & Precautions

Possible Interactions
The antiinflammatory activity of this herb can be seriously inhibited by phenobarbital and certain other sedatives and hypnotics (chloral hydrate, meprobamate, etc.), as well as beta-adrenergic blocking agents, such as propranolol.

Colchicine may increase sensitivity or enhance the response to yam plant.

Comments
Oral estrogen supplementation may retard the metabolism of yam plant's steroidal hormones.

Safety Factors & Toxicity

The use of wild yam as a food supplement in normally recommended amounts is safe. The use of larger amounts may run the risk of metabolic changes due to the presence of dietary DHEA. Pregnant women should avoid it. DHEA may interfere with the metabolism of alcohol and barbiturates in the liver.

Preparation & Administration

Use three times daily

Infusion or Decoction
Use 2-4g of dried root

Liquid Extract
Use 2-4ml of 1:1 in 45% alcohol

Tincture
Use 2-10ml of 1:5 in 45% alcohol

References

British Herbal Pharmacopoeia, British Herbal Medicine Association, 1983.

Lewis, D.A. Anti-inflammatory Drugs for Plant and Marine Sources, Birkhouse Verlag, Berlin, 1989.

Mowrey, Daniel B., Ph.D. Exper. Psych., Brigham Young University. Director of Nebo Institute of Herbal Sciences. Director of Behavior Change Agent Training Institute. Director of Research, Nova Corp.

Shulutko, I.B., L.Y. Tugbaeva & V.A. Nesterov. Therapeutic efficiency of dioscorea saponins in the treatment of patients with atherosclerosis. Drugs of Plant Origin. A.D. Turlova, ed. Moscao: Medgiz, 1962, pp. 143-145 In Russian.

Simonova, J., I. Gregorova & J. Sonka. Metabolicke komplekace otylosti-pokus o jejich ovlivneni dehydroepiandrosteron sulfatem. Sbornik Lek., 75, 27-30, 1973.

Sokolova, L.H. Effect of saponins on the development of experimental atherosclerosis. Farmakologia I Toxikologia, 21(6), 85-90, 1958.

Sokolova, L.N., V.I. Kichenko, et.al. Diosponine--a new drug for treatment of patients with atherosclerosis. Med. Prom., 7, 43-48, 1961. In Russian.

Weiss, R.F. Herbal Medicine. Beaconsfield Publishers, LTD, Beaconsfield, England, 1988.

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Dioscorea


Yam 2.

? Southwest School of Botanical Medicine

 


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