The Wild Yam a review
Anthony C. Dweck FLS FRSH FRSC
Personal Care Magazine 3, 3, p.7-9. (2002).
The Wild Yam review of Dioscorea species.
Introduction
When it was decided to review the wild yam and related Dioscorea species it was
probably in ignorance of the complexity of the task. This is a fascinating plant with
many uses in folk lore and also in the history of the development of modern
pharmacy. The number of species is quite overwhelming (over 600) and the
ethnobotanical use most interesting.
Species and their names
The most well known species is Dioscorea villosa, also called Wild Yam Root, Colic
Root and Rheumatism Root [British Herbal Pharmacopoeia] .In Chinese it is called
Huang Yao Tzu, Shu Yu [Raintree]. Other sources refer to it as China Root, Devil's
Bones, Yuma, Mexican Yams [Lust; Trickey], Wilde Yamwurzel [Grieve] and in the
United States it is called the Atlantic Yam and Wild Gum Root [Krochmal et al]
Other species include: Amongst the medicinal yams, Dioscorea villosa and
occasionally hirticaulis are mentioned in English pharmacopoeias [Fisher et al.];
Dioscorea villosa, spiculiflora and floribunda in the American [Willard]; Dioscorea
opposita (D. batatas) or Chinese Yam, Shan Yao (mountain medicine) in Chinese
[Reid; Chevalier], and Dioscorea japonica in J apanese [Yen] texts, although it is also
known as Chinese Yam [Keys]. All of these Dioscorea spp. have similar indications,
but those species used as part of Traditional Chinese Medicine have additional
actions. Dioscorea nipponica and D. caucasia are not commonly used in Western
herbal medicine.
Dioscorea transversa (punctata) is an Australian member of Dioscorea spp., which
has been used topically for skin cancer. [Lassack et al.]
Dioscorea dregeana or inGcolo in Pondo and Xosa [Watt et al] seems to be the
plant of choice in South Africa [Wyk et al.], while in tropical West Africa the plant of
choice is Dioscorea dumetorum (Kunth) Pax. (Syn: Helmia dumetorum, Dioscorea
buchholziana Engl.) or the Bitter Yam or Cluster Yam. [Oliver-Bever], this species is
also used in Sekukuniland and known as sekanama by the Giftulp and Venda
people [Watt et al]. Another species Dioscorea sylvatica or inGweru is also used
by the Zulus and also rarely Dioscorea rupicola or inKwa. In Malawi, Dioscorea
bulbifera L. - Air Potato or Potato yam (Fikengere) [Williamson]. This plant is also
employed in the Philippines, where it is known as Aribukbuk; Bayag-Kabayo;
Dadakan; Pulugan; Ubi-Ubihan; Utong-Utangan. [Quisumbing]
In the Philippines another species is also used Dioscorea esculenta (Lour.) Burkill or
Tugi, Aneg; Boga; Dukai; Kamiging; Luttu; Tongo; Tungo. They also have
Dioscorea hispida Dennst., or Nami, Bagai; Gagos; Kalut; Karat; Karoti; Kayos;
Kalot; Korot, Kulot; Mamo; Nami; Orkot.
In the South American rainforests the Dioscorea aff. belizensis Lundell or Cocolmecca
or Barba del Viejo is found [Arvigo et al.]. The Waimiri Atroari Indians of Brazil
favoured Dioscorea trifida [Milliken et al].
In India it is Dioscorea pentaphyla or Nureni-kelangu, Kanta-aloo that is employed
[Drury] as well as D. fasciculata (Boxb.), which is cultivated largely in the vicinity of
Calcutta, where it is known as the soosni-aloo. Another kind is the D. purpurea
(Boxb.), known as the Pondicherry Sweet Potato.
Dioscorea deltoidea and D. prazeri are also used, which are known as Chingali
Mangali, Ban Tarul, Kukkar Tarul in Hindi [Thakur]. Other exotic species like D.
floribunda and D. composita, and their forms are being cultivated.
The uses of Dioscorea villosa
The original use of Wild Yam was as a source of the raw material used for
contraceptive manufacture. Species of Dioscorea were also used as sources of
saponins for the preparation of steroids in the pharmaceutical industry [Wren].
In herbal medicine the root is used for intestinal colic (and indigestion), to soothe
diverticulitis, relieve dysmenorrhoea, as well as allay uterine and ovarine pain. The
most significant use is in the treatment of rheumatoid arthritis to relieve the intense
inflammation in the acute phase [British Herbal Pharm.]. It is also used for muscular
rheumatism [Krochmal] and spasmodic asthma [Foster & Duke; Grieve], as well as
things as remote as the chronic gastritis of drunkards!
Extracts of Wild Yam are also said to be of help to women with menopausal and PMS
symptoms [Watson]. It is also said to be good for labour pains and the prevention of
early miscarriage. The American Indians use a root decoction to relieve the pain of
childbirth [Krochmal], other sources say that it is good for the nausea that can be
experienced during pregnancy [Lust].
It is such a good antispasmodic that it can be used for cramps, coughs and hiccoughs
[Trickey] and for muscular spasms, croup and gas. It is considered good for loosening
phlegm, inducing vomiting and increasing urine flow.
Others say it is good for fatigue [Raintree] and is also soothing to the nerves [Lust]
There have been studies to show that Dioscorea has antioxidant activities
[Araghiniknam et al] and the anti-inflammatory activity can be linked to the
antiphlogistic effect of the steroidal saponins.
Some species of Dioscorea show antibacterial activity against Gram-positive bacteria
and Gram-negative Escherichia coli, though specifically for D. sylvatica and D.
dregeana [Kelmanson].
The plant is also cited with cardiovascular activity, hepatic effects and hormonal or
oestrogenic effects.
Widely prescribed cortisones and hydrocortisones were indirect products of the genus
Dioscorea. They are used for Addisons disease, some allergies, bursitis, contact
dermatitis, psoriasis, rheumatoid arthritis, sciatica, brown recluse spider bites, insect
stings, and other diseases and ailments. [Foster & Duke]
Usage levels
Prepare a decoction with 3-9g of the root or use 10-30 drops of tincture [Watson].
By infusion or decoction 6 12g/day of the dry herb
The extract should be used at a level of between 20 40ml per week (1:2)
Liquid extract, dose 2 4ml [Wren]
Infusion: Steep 1 tsp root in 1 cup water for 30 minutes. Take 1 cup in the course of the
day, a mouthful at a time. [Lust]
Tincture: Take 10 to 30 drops in water, three or four times a day as needed. [Lust]
0.5 1 drachm of fluid extract. Dioscorein 0.25 to 4 grains. [Grieve]
Chemical composition
The wild growing Mexican Yams, Dioscorea floribunda and D. composita are
believed to yield the most diosgenin and are used for commercial purposes.
Dioscin
The activity of Dioscorea species has been attributed to the action of various steroidal
saponins (diosgenin an aglycone) and also to dioscorin(e), dioscin(e) and other alkaloids
derived from nicotinic acid.
Dioscorine
Diosgenin
The root also contains phytosterols, alkaloids, tannin and a high level of starch. Other
materials include Aluminum, Ascorbic-acid, Ash, Beta-carotene, Calcium, Chromium,
Cobalt, Iron, Magnesium, Manganese, Niacin, Phosphorus, Potassium, Protein,
Riboflavin, Selenium, Silicon, Sodium, Thiamin, Tin, Zinc
Conclusions
It is highly unlikely that the diosgenin in the plant could ever be synthesised on the
topical application to the skin to form a corticosteroid or hormonal derivative. However,
it does seem likely that this material (being the precursor to these estrogenic molecules)
will to some extent mimic the function of that pharmaceutically active material and
benefit the skin.
There is no doubt that the phytosterols (of which diosgenin is a member) will give
soothing and anti-inflammatory effect to the extract and so be a very useful topical
additive to a skin cream for mature and dry skin types. This is being borne out in some
of the latest studies being published on Wild Yam extracts targeted at the skin care
formulator.
The ever ageing skin care market and the increasing proportion of consumers over 50
years of age will undoubtedly trigger a need for specific products to satisfy these more
mature skin types. Wild yam, soy and pomegranate all contain diosgenin and so stand a
good chance of being ideal for this market. A survey of the literature also highlighted
ginseng as a potential source of this material, but the level was not specified.
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