||Wild Yam (English)|
Dioscoreaceae (Plant Family)
Dioscorea villosa, commonly known as wild yam, is native to Canada and
the southern United States. It is one of an estimated 600 species of yam in the
genus, Dioscorea, found in warm tropical habitats. Many of these are wild
species that flourish in damp woodlands and thickets.
Yams are important cultigens, and some yam species are major food staples in
tropical countries. The potato-like tubers of yam plants are grown as both
edible and ceremonial plants throughout the world, even in subtropical and
temperate regions. The formation and morphology of the tubers can vary from
species to species. The tubers of Dioscorea villosa, for example, arise
as fleshy rhizomes.
The tubers of wild yam and certain related species contain saponin compounds,
including steroid-like constituents that are used as starting material for the
synthesis of hormones. Wild yam tubers contain diosgenin, a steroid precursor
that can be converted into the female hormone progesterone in the
The discovery of diosgenin revolutionized the pharmaceutical industry several
decades ago. It paved the way for synthesizing hormones and developing oral
contraceptives. Today, diosgenin is still used as an active industrial agent in
the half-synthesis of steroidal hormones. This chemical compound was
traditionally obtained from Mexican yam (Dioscorea mexicana), but
it is also present in wild yam (Dioscorea villosa). Wild species of yam
tend to contain higher concentrations of diosgenin than do cultivated, edible
A closely related species of wild yam, Dioscorea alata, is used in the
Amazon as a treatment for fever, gonorrhea, leprosy, piles, and tumors.
Amazonian medicinal plant remedies made from other Dioscorea species are
administered for skin inflammation, stomachache, boils, cancer, dysentery,
goiter, and syphilis. In Belize, a "wild yam" species
(Dioscorea belizensis) is a popular treatment for urinary tract
infections, cold, bilious colic, rheumatism, arthritis, and diabetes.
Both cultivated and uncultivated yam species are employed in folk medicine
for a wide variety of ailments. Diosgenin is conceivably responsible for
pharmacological activities such as the purported anti-inflammatory effects of
wild yam. The tubers of Dioscorea villosa and other wild yam species have
a long history of use in traditional herbalism, but their importance will
forever be linked to modern medicine. The synthesis of hormones and the birth
control pill from diosgenin marks one of the major advances in plant drug
medicine this century. This discovery helped to legitimize
ethnopharmacology—the search for pharmaceutical drugs
from natural products, particularly natural products from the plant kingdom.
Wild yam is a perennial, twining vine with pale brown, knotty, woody,
cylindrical rootstocks, or tubers. The rootstocks are crooked and bear lateral
branches of long creeping runners. The thin reddish-brown stems grow to a length
of 5 to 12 meters. The tubers have no characteristic odor. The roots initially
taste starchy, but soon thereafter become bitter and acrid to the tongue.
The wild yam plant has clusters of small green-white to green-yellow single
flowers that are sessile-like. The heart-shaped leaves are broadly ovate and
long-stemmed, with prominent longitudinal veins. The leaves are glabrous on the
upper surface and pubescent on the underside.
Part Used/Pharmaceutical Designation
Dioscorea villosa roots contain saponins (e.g., dioscin,
an aglycone diosgenin), isoquinuclidine alkaloids (e.g., dioscorin)
Commercial preparations of wild yam are available as liquid extracts and
powdered tuber products. Raw plant material for commercial use is typically
harvested from the eastern and central United States, and supplied to commercial
outlets in the form of cut or broken tubers.
Traditional uses: used as anti-inflammatory, cholagogue (stimulates flow of
bile to duodenum), antispasmodic, carminative, sudorific, mild diaphoretic
(perspiration-promoting agent), anodyne (analgesic), emetic (vomit-causing
agent), expectorant; used for rheumatic conditions, gallbladder colic,
dysmenorrhea, cramps, asthma, diuretic, dyspepsia, liver ailments, parturition,
uterotonic, pain and inflammation of diverticulai, bilous colic, nausea
associated with pregnancy, cramps, neuralgia, spasmodic hiccup, spasmodic
asthma, women's reproductive health (e.g., salve made from inner root applied
topically for breast inflammation and postmenopausal vaginal dryness).
Conditions: inflammation, spasm, rheumatic conditions, cramps; mild
Clinical applications: anti-inflammatory, cholagogue, antispasmodic, mild
diaphoretic, rheumatic conditions, gallbladder colic, dysmenorrhea, cramps,
biliousness, nausea, intestinal colic.
Although various species of Dioscorea have been investigated
extensively for their pharmacological properties, relatively few published
studies were located on Dioscorea villosa. Various preparations of wild
yam reportedly have exhibited anti-inflammatory, antitumor, estrogenic,
hemolytic, hypocholesterolemic, amebicidal, mastogenic (pertaining to breasts),
pesticidal, and piscicidal effects. However these claims have not necessarily
been confirmed by laboratory research. Similarly, the putative antifatigue,
antistress, and antigliomic (antitumor against cancers of brain and nervous
tissue) effects of wild yam await further scientific verification.
However, studies on other species of Dioscorea clearly show that a
related species of wild yam has antidiabetic activity. In one investigation, the
effects of hydroalcoholic extracts of Dioscorea dumetorum tubers were
evaluated on either fasting normal mice or rabbits, and on fasting
alloxan-diabetic rabbits. Both the whole extract and the steroidal fractions,
especially the glycosidic portion, produced significant hypoglycemic action in
normal test animals and in fasting alloxan-diabetic rabbits. A fraction
containing alkaloids actually elevated blood sugar in the fasting normal mice.
This suggests that the active constituent responsible for the hypoglycemic
effect is probably a steroidal derivative. Nigerian researchers have also
reported that Dioscorea dumetorum tubers possess antidiabetic properties.
|Dosage Ranges and Duration of
- Dried herb: 1 to 2 tsp tid
- Tincture: 2 to 4 ml tid
No adverse side effects have been reported for wild yam preparations when
taken in recommended therapeutic dosages.
Overdosing can be potentially poisonous because dioscorin, one of the active
constituents, can have picrotoxin-like effects.
Dietary provisions of diosgenin (1% w/w) for 6 days reduced the cholestatic
(1.1 mmol/100g IV) in rats (Accatino et al. 1998). In
addition, the diosgenin-supplemented diet prevented some of the cholestatic
effects of 17 a-ethynylestradiol (5 mg/kg
subcutaneously), such as increased biliary alkaline phosphatase and decreased
|Regulatory and Compendial
Wild Yam is listed in the British Herbal Pharmacopeia.
Accatino L, Pizarro M, Solis N, Koenig C. Effects of diosgenin, a plant
derived steroid, on bile secretion and hepatocellular cholestasis induced by
estrogens in the rat. Hepatol. 1998;28(1):129-140.
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Arvigo R, Balick M. Rainforest Remedies: One Hundred Healing Herbs
of Belize. Twin Lakes, Wis: Lotus Press; 1993: 194-195.
British Herbal Pharmacopoeia. 4th ed. Great Britain: Biddles Ltd,
Guildford and King's Lynn; 1996:187.
Dorland's Illustrated Medical Dictionary. 25th ed. Philadelphia, Pa:
W.B. Saunders; 1974.
Duke JA. The Green Pharmacy. New York, NY: St Martin's Press;
1997:111, 209-210, 352
Duke JA. Phytochemical Database,
Agricultural Research Center, Md. Available at:
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Fla: CRC Press; 1994:66-67.
Etkin N, ed. Plants in Indigenous Medicine and Diet: Biobehavioral
Approaches. Bedford Hills, NY: Redgrave Publishing; 1986: 131-150.
Grieve M. A Modern Herbal. Vol. II. New York, NY: Dover; 1971:863.
Gruenwald J, Brendler T, Jaenicke C. PDR for Herbal Medicines.
Montvale, NJ: Medical Economics Company; 1998:809-810.
Mabberley DJ. The Plant-Book: A Portable Dictionary of the Higher
Plants. England: Cambridge University Press; 1987: 185
Thomson WA, ed. Medicines from the Earth: A Guide to Healing Plants.
Maidenhead, England: McGraw-Hill Book Company; 1978:61.
Vasiukova N, Paseshnichenko V, Davydova M, Chalenko G. Pharmacological
evaluation of Dioscorea dumetorum tuber used in traditional antidiabetic
therapy. J Ethnopharmacol. 1986;15(ISS
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