ABOUT AUTHORS:
Prashanta kr. Deb1, Tejendra Bhakta2*,
1Dept. of Pharmacy, Tripura University; Suryamaninagar –799 022, Agartala, Tripura (w).
2Regional Institute of Pharmaceutical Science & Technology, Abhoynagar – 799005, Agartala, Tripura (w).
shaandeb2010@gmail.com
INTRODUCTION
Dioscorea is a slender twining annual herbs distributed throughout the tropical and subtropical region of the world. Dioscorea is a fascinating plant with many uses in the history of the development of modern pharmacy. The number of species is quite overwhelming (over 600) and the Ethno-botanical uses are most interesting. Dioscorea is a genus of over 600 species of flowering plants in the family Dioscoreaceae. They are tuberous herbaceous perennial climber, growing to 2–12 m or more tall. The leaves are spirally arranged, mostly broad heart-shaped. The flowers are individually inconspicuous, greenish-yellow, with six petals; they are mostly dioecious, with separate male and female plants, though a few species are monoecious, with male and female flowers on the same plant. The fruit is a capsule in most species, a soft berry in a few species. Several species, known as yams, are important agricultural crops in tropical regions, grown for their large tubers. Some species produces large cylindrical tubers penetrating deep into the ground, while other varieties produce small or large tubers close to the soil surface. Sometimes 1-2 tubers are produce at the base of the plant while in the other cases cluster of tubers are observed. Many of these are toxic when fresh, but can be detoxified and eaten, and are particularly important in parts of Africa, and Asia.
REFERENCE ID: PHARMATUTOR-ART-1657
GEOGRAPHICAL DISTRIBUTION
Dioscorea is grown up to the altitude of 8000-15000 ft. above the sea level and normally does not grow in warm places. Yams are cultivated as garden crops by using both tuber tops and aerial tubers (bulbils), but the tuber crops are better for the rapid growing than the bulbils. A number of cultivated plants as well as wild varieties of yams are available throughout the state of Tripura. A different wild variety of yams grows in the forest of Tripura, which is yet to identify and evaluate for their food values. Tribal’s collect these yams from the dense forest during food scarcity.
Dioscorea alata is the most important species among the cultivated yams. It is grown as garden crops in every parts of Tripura. Yam grows abundantly in the several tracks and forest areas of Tripura. Dioscorea fasciculate is specially concentrated in the hilly forest region. The forest regions of Tripura like Kamalpur, Kailasahar, Sabroom, Belonia, Amarpur, Jampui, Longtarai etc. are the main places where the Tribals cultivate the yam and it also grows naturally.
In view of the pharmaceutical significance of drug, it is tried and successfully grown in various parts of India. Commercially, it is grown in Sikkim, Assam, Manipur, Arunachal Pradesh,Tamil Nadu, west Bengal, Maharashtra, Karnataka, and Jammu and Kashmir. D. deltoidea is found growing in north-western Himalayas from Kashmir and Punjab to Nepal and china upto an altitude of 1000 to 3000 m. It is cultivated in Jammu and Kashmir and in part of Himachal Pradesh. D. deltoidea is also found in U.S.A. and Mexico.
HISTORY OF DIOSCOREA
"At the battle of Trenton in December, 1776, General Washington captured a large number of Hessian prisoners. Among them was a botanic physician, Dr. Bone, who subsequently settled in New Jersey, a few miles above the city of Newark. To him belongs the credit of first using the Dioscorea villosa as a medicine. He appears to have used it for a long time as a secret remedy for bilious colic, and from his success in the administration of the medicine in this disease, he named it colic root. He gave to the patient half a tea-cup full of the decoction, every half-hour; the second dose rarely failed of curing this truly formidable disease."
The above from the transactions of the Eclectic Medical Society of New York State, 1870, by Dr. D. E. Smith, of Brooklyn, is part of the most complete paper on Dioscorea to that date. Just where Dr.Smith obtained his reference to Dr. Bone we have been unable to find. The qualities of this drug were first authoritatively recorded in a book devoted to Materia medica, by Horton Howard. In the 18th and 19th centuries, herbalists used wild yam (Dioscorea villosa) to treat menstrual cramps and problems related to childbirth, as well as for stomach upset and coughs. In the 1950s, scientists discovered that the roots of wild yam (not to be confused with the sweet potato yam) contain diosgenin, a phytoestrogen (derived from plants) that can be chemically converted into a hormone called progesterone. Diosgenin was used to make the first birth control pills in the 1960s.Although herbalists continue to use wild yam to treat menstrual cramps, nausea, and morning sickness associated with pregnancy, inflammation, osteoporosis, menopausal symptoms, and other health conditions, there is no evidence that it works. Indeed, several studies have found that it has no effect at all. That is because the body cannot change diosgenin into progesterone; it has to be done in a lab. Wild yam, by itself, does not contain progesterone.
SELECTIVE SPECIES AVAILABLE IN TRIPURA
1. Dioscorea alata. (Eng: greater yam, Beng; Chupri alu, Kokborok; Thaduk).
2. Dioscorea bulbifera. (Eng; Potato yam, Beng; Banalu, Kokborok; Thwngwi).
3. Dioscorea puber. (Beng; Kukuralu, Hindi; Kasa alu, kokborok; Thacher).
4. Dioscorea hamiltonii ( Kokborok; Thakun)
5. Dioscorea esculenta. ( Eng; Lesser yam, Beng; Susnialu, kokborok; Thaktwi waksa)
6. Dioscorea pentaphyla ( Beng; Jhunjuna lata, Hindi; Kantaalu, kokborok; Kwiccha)
7. Dioscorea fluribenda (Beng:Gada alu).
8. Dioscorea glabra (Rheumatoid yam).
NUTRITIONAL VALUES
Most of the species of Dioscorea are used as vegetables in the same manure as the potato. The tubers of Dioscorea constitute a chief source of Carbohydrates mainly starch (75%). Tubers are used as famine food by the Tribals of Tripura. Some species like D. esculenta are sweet in taste. Tribals consume this Yam simply by boiling. Some species are poisonous. Tribals peeled and boiled properly to eliminate the alkaloid or other poisonous principles during cocking. Tribals of Tripura make different delicious dishes with these yams. Analysis of the edible tubers of Dioscorea showed the following values: Moisture (66-82%), Protein (1-2%), Fat (0.1-0.3%), Carbohydrate (18-25%), Minerals (0.5-1%), Fibers (o.1-1.5), Energy (65-124 Kcal/100gm), Calcium (16-52 mg/100 gm), Phosphorus (24-74 mg/100 gm), Iron (0.5-1 mg/100 gm), Niacin (1-1.5 mg/100 gm), VitaminC (1 mg/100 gm), Thiamin (0.1-o.2 mg/100 gm), Riboflavin (0.5mg/100 gm), Carotene (565µg/100 gm) Etc.
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PHYTOCHEMISTRY OF DIOSCOREA
Dioscorea rhizomes contain 75% of starch. The chief active constituent of dioscorea is diosgenin, a steroidal sapogenin (4 to 6 %), and its glycosides, smilagenin and epismilagenin and β-isomer yammogenin. Rhizomes are also found to contain an enzyme sapogenase. Tubers are also rich in glycosides, and phenolic compounds. Diosgenin is the hydrolytic product of saponin-dioscin. The activity ofDioscorea 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. The root also contains phytosterols, alkaloids, tannin and a high level of starch. Other materials include Aluminium, Ascorbic-acid, Ash, Beta-carotene, Calcium, Chromium, Cobalt, Iron, Magnesium, Manganese, Niacin, Phosphorus, Potassium, Protein, Riboflavin, Selenium, Silicon, Sodium, Thiamin, Tin, Zinc etc.
ISOLATED PHYTOCONSTITUENTS
The tubers are dried, powdered and hydrolysis of dioscin is done by mineral acids. The liberated diosgenin is extracted with the help of non-polar solvents like benzene or solvent ether. After isolation, diosgenin is degraded to 16-dehydro pregnenelone acetate. This latter molecule is used as precursor for synthesis of: Corticosteroids like cortisone, hydrocortisone, Pregnenes like progesterone, 17-α –hydroxy progesterone, Androstanes like testosterone, methyl testosterone, etc. and 19-NOR steroids like estrone, 17 – α ethynyl estradiol and norethisterone acetate.
Fourteen new compounds were isolated and identified for first time as stigmasterol (1), mono-arachidin (2), 1,7-bis-(4-hydroxyphenyl)-1E,4E,6E-heptatrien-3-one (3), behenic acid (4), demethyl batatasin IV (5), 2,3'-di-hydroxy-4',5'-dimethoxybibenzyl (6), diosbulbin B (7), diosbulbin D (8) docosyl ferulate (9) 7-bis-(4-hydroxyphenyl) -4E, 6E-heptadien-3-one (10) 5,3,4-trihydroxy-3,7-dimethoxyflavone (11) tristin (12) protocatechuic acid (13) adenosine (14).
MEDICINAL AND THERAPEUTIC USES
Folklore uses:Powdered tubers used as a remedy for piles, gonorrhea and applied on sores.
Antioxidant activity:Tubers of Dioscorea are used as Antioxidant.
Bowel function benefits:Study showed 25% to 59% yam diet increased fecal mass and SCFA output, modulated fecal microflora and thickened caecal mucosal lining in mice.
Antihypertensive activity:Dioscorin, the tuber storage protein of yam and its hydrolysates presents potential use for hypertension control.
Cholesterol lowering activity:Study showed reducing effects of 50% yam diet on plasma and hepatic cholesterol levels probably through inflated fecal fat and steroid excretion.
Cytokine-mimetic property:Study showed that from extracts of yam roots and leaves strongly stimulated proliferation of both bone marrow cells and splenocytes, significantly increasing Cell concentrations.
Estrogenic effect in menopausal women :In a study of menopausal women with rice staple diet replaced by yam (D alata) for 30 days showed improvement in status of sex hormones (estrone, sex hormone binding globulin, estradiol), blood lipids and antioxidants suggesting possible benefits in reducing breast cancer and cardiovascular disease in postmenopausal women.
Bone-Protective effect:Yam prevented loss of BMD (bone mineral density) and improved calcium status.
Renal Protective / Hepatoprotective:Pharmacological and biochemical studies showed yam have both renal protective and hepatic fortification effects in acetaminophen rats. Results provide basis for the use of yam in traditional Chinese medicine for the treatment of renal and hepatic disorder.
Hypo-Triglyceridemic effect:Yam may inhibit the acute induction of hypertriglyceridemia and liver enlargement.
CONCLUSION
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.
Not only that, the other medicinal and therapeutic uses of Dioscorea like as folklore, antioxidant, in gastro-intestinal disorder, ACE-inhibitor, cholesterol lowering agent, renal and hepato-protective, estrogenic and bone-protective activity make this vegetable drug so precious that it definitely can entitled as the multidrug. The presence of Diosgenin, Dioscin, and Dioscorin, all these steroidal components and their extraction and isolation for the pharmaceutical uses widely exposes the economic demand of Dioscorea. Commercially Diosgenin is very much valuable. The contraceptive activity is very much highlighted in the pharmaceutical market. As we know that Dioscorea contains a high grade of starch (75%), which we can be used as a substitute source of Maize, Rice and potato starch. Pharmaceutical study already showed that Dioscorea starch has a better binding agent and disintegrator activity than the other sources.
Over the entire world Dioscorea is widely available. In our Tripura also it is available in the several tracks and in the interior sides. Most probably more than 15 species of Dioscorea are available in Tripura, out of which 8 we have already isolated. Different countries already started to isolate and market the Diosgenin from Dioscorea. The other above mentioned therapeutic uses predict this vegetable as a miraculous vegetable drug. So, if we proceed for the cultivation, collection, conservation and proper phyto-chemical analysis of Dioscorea, it will be a bigger issue for our medicinal as well as the economic status development of our country.
REFERENCES
(1) Kirtikar KR, Basu BD. Indian Medicinal Plants. Vol.II. Bishen Singh Mahendra Pal Singh, Dehra Dun-248001, 1980.
(2) Ghosh GK. Herbs of Manipur. Vol.II A.P.H. Publishing Corporation, New Delhi-110002, 2000.
(3) A Dictionary of Indian Raw Materials and Industrial Products, The Wealth Of India. Vol.VII. Publication and Information Directorate, CSIR, New Delhi-12, 1997.
(4) RN, Chopra “Glossary of Medicinal Plant”, C.S.I.R. New Delhi, 1956.
(5) The Ayurvedic Pharmacopia of India part-Ivolume –III first edition.
(6) The wealth of India a raw material, volume-3: CSIR New Delhi, Revised edition 1992.
(7) DB Deb, The Flora of Tripura State, Vol I&II (Today and Tomorrows Prrinters, New Delhi).
(8) K. Majumder, R. Saha, B.K. Dutta, T. Bhakta; Medicinal Plants prescribed by different Tribles and non-tribles medicine man of Tripura State: Indian Journal of Traditional Knowledge Vol 5(4) October 2006, pp 559-562.
(9) Majumder K, Ethnobotanical Survey of some traditional medicinal plants and their environment around tribles areas of Tripura State, M.Sc. thesis. Sikkim Manipal University, 2003-2004.
(10) Bhakta, T., “Common Vegetables of The Tribals of Tripura” First Edn., Tribal Research Institute, Government of Tripura, 2004, p. 43-50.
(11) Pharmacognosy C. K. Kokate, A.P. Purohit, S.B. Gokhale, Thirty-Seventh Edition Page No 209-210.
(12) Antioxidant activity of dioscorea and dehydroepiandrosterone (DHEA) in older humans. Life Sci. 1996; 59 (11):PL147-57.
(13) Effects of "Chinese yam" on hepato-nephrotoxicity of acetaminophen in rats. Acta Pharmacol Sin. 2002 Jun; 23(6):503-8.
(14) Nutritional assessment of yam (Dioscorea alata) tubers Plant Foods Hum Nutr. 1994 Jul; 46(1):33-9.
(15) Yam (Dioscorea batatas) tuber mucilage exhibited antioxidant activities in vitro. Planta Med. 2002 Dec;68(12):1072-6.
(16) Antioxidant activities of dioscorin, the storage protein of yam (Dioscorea batatas Decne) tuber. J Agric Food Chem. 2001 Oct; 49(10):4956-60.
(17) Dioscorin, the major tuber storage protein of yam (Dioscorea batatas decne) with carbonic anhydrase and trypsin inhibitor activities. J Agric Food Chem. 1999 May; 47(5):2168-72.
(18) Anticancer effects of various fractions extracted from Dioscorea bulbifera on mice bearing HepA. Zhongguo Zhong Yao Za Zhi. 2004 Jun;29(6):563-7.
(19) Antitumor-promoting constituents from Dioscorea bulbifera L. in JB6 mouse epidermal cells. Biol Pharm Bull. 2002 Sep;25(9):1241-3.
(20) Pharmacological evaluation of Dioscorea dumetorum tuber used in traditional antidiabetic therapy. J Ethnopharmacol. 1986 Feb; 15(2):133-44.
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