Nami is a twining vine, arising from tuberous roots,
and reaching a length of several meters. Stems covered with few or many
short, sharp spines. Leaves are 3-foliolate, the leaflets 12 to 20 centimeters long, somewhat
hairy, the lateral ones oblique, oblong-ovate, the terminal one equilateral, oblong to oblong-obovate. Panicle is axillary, slender, hairy, 12 to 20 centimeters long. Flowers are small; unisexual male flowers with 6 stamens; female
flowers similar to males, 3-winged, 3-celled, ovules 2 in each cell.
Fruit is a capsule, oblong and about 5 centimeters long. Flesh and sap of tubers are yellowish.
- Growing wild, chiefly in thickets
and forests at low and medium altitudes throughout the Philippines.
- Rarely cultivated.
- Occurs in India to China and Taiwan and through Malaya to New Guinea.
- Tubers yield alkaloid dioscorine a and 4-epidioscorine and a neuromuscular blocking agent.
- Study yielded a saponin glycoside, diosgenin.
The primary active ingredient in Dioscorea species, diosgenin is D. hispida is reported at 57µg/g dw.
- Study of mineral content reports the tubers are a good source of phosphorus, calcium and iron.
- A mature gadung tuber weighs up to 15 kg, each 100 g of tuber (wet basis) yields 20 g of carbohydrates, 78 g water, 1.81 g protein, 0.16 g fat, 0.93 g fiber and 0.69 ash.
- Extracts of tubers yielded hydroxybenzoic acid, hydroxycinnamic acid, and their derivatives. Peel yielded caffeic acid, chlorogenic acid, p-hydroxybenzaldehyde and methylester of protocatechuic acid. Phenolic acid content of both peel and flesh were very low. (11)
- Resistant starch is slowly digested in the lower parts of the GIT, with slow release and absorption of glucose. Starch is also gluten free.
- Sweet tart-tasting, cooling.
- Yellow flesh tubers reported to have a better taste than white flesh tubers.
Flesh and sap of the tubers are yellowish.
- Juice of underground stems reported to possess narcotic properties.
- Studies suggest anthelmintic, antioxidant, anti-inflammatory, analgesic, and anti-tumor activities.
- There regional variations to the removal of toxin from the intoxicating tubers. Pulau Redang has several detoxification techniques. One requires thin slicing of yam, the soaking it in salted water for three days, then placing it in a sac to re-soak in a river or flowing water for another three days, finally testing edibility to see if fish would feed on them.
- In Papua New Guinea, the tubers are sliced and boiled for two days before cooking the yam.
- In Thailand, the Sakai remove the toxin by boiling with wood ashes.
- Underground tubers.
Edibility / Nutrition
- Tuber crop is an important source of carbohydrates; has been used a staple foods during WWI.
- Despite known toxicity, in Thailand, where it is referred to as Kloi, tubers are used to make a dessert called Kao Nuew Kloi.
- In Kerala, India, tuberous herb cooked with salt, chili, tamarind and tumeric powder and used as curry.
- Caution: See toxin removal.
- Tuber, raw or cooked used as anodyne and maturative for tumors and buboes.
- Also used
arthritic and rheumatic pains. sprains and contusions.
- Use poultice of freshly pounded material or decoction as external wash.
- In Bangladesh, tubers used to kill worms in wounds. Various plant parts used in whitlow, sores, boils, and bites of rabbit, jackal or dog.
- In India, tubers used for birth control.
- In Malaysia, pounded leaves applied to sores of yaw.
- In Johore, decoction of tuber used as alterative and diuretic in chronic rheumatism.
- In Malaysia, the Temuan tribe uses pounded leaves from intoxicating yam for healing sores of yaw.
Infusion of corms of detoxicated tubers used to decrease blood glucose. Tendril of yam have been used as deworming medicine.
• Bleaching: Yellow juice from the flesh and sap of tubers is used for bleaching
clothes and abaca fibers.
• Poison: Juice of tubers used in criminal poisoning.
Also, used as an ingredient together with Antiaris toxicaria in the preparation of arrow poisons.
• Intoxicant: Jeypore people of India reportedly use the intoxicating effect of D. hispida to forget their sorrows, as they get an effect similar to drinking beer.
• Insecticidal: Residue after extraction of poison used as insecticidal.
• Livestock: Tubers used as cure for myiasis of the scrotum in carabaos.
• Phytochemicals / Phenolic Content:
Study showed phenolic acids were present in only small amounts in Kloi tuber, compared to relatively high phenolic content for other yam Dioscorea species. The anomaly was attributed to the sample preparation, hydrolysis time and/or pH. Preliminary findings and documented nutritive value suggest the tuber as a potential source of phytochemicals for cosmetic, pharmaceutical or dietary antioxidant use. (2)
• Anti-Inflammatory / Analgesic:
Study of extract of D. hispida in animal models showed potent analgesic and anti-inflammatory effects and therapeutic efficacy, comparable to standard drugs Pentazocine and indomethacin respectively. (3)
• Toxicity Study: Study
of ethanolic extract showed no toxicity or death at given test dose levels. LD50 was >2000 mg/kbw for the extract.
• Hypoglycemic Effect: Study in alloxan-induced hyperglycemic rats evaluated the hypoglycemic effect of a water soluble polysaccharide extracted from yam tuber (D. hispida). All the WSP extracts exhibited an ability to decrease blood glucose in hyperglycemic condition as well as inhibit glucose absorption and short chain fatty acid (SCFA) formation. (4)
• Gadung Starch / Modification with Raw and Ginger Oil: Use of starch is limited by its high content of toxic substances, i.e. alkaloids and hydrogen cyanide in free and bound forms, high moisture content and a disposition to post harvest deterioration. Previous efforts have been successful in reducing the bitter and toxic compounds to a safe level. Study showed processing and modification resulted properties comparable to American wheat flour. One drawback was the presence of remaining ginger aroma. (7)
• Pharmacologic Effects of Extracts: Purified extracts studied in animals showed: (1) Properties resembling nicotine (2) Injection caused hyperpnea, tachycardia, increase in blood pressure, contraction of nictitating membrane. (3) Rise in BP and contraction of nictitating membrane and of smooth muscle were inhibited by pretreatment with hexamethonium. (4) Striated muscle contraction was inhibited by pretreatment with d-turbocurarine.
• Antitumor / Antioxidant: Study evaluated D. hispida against an animal model of Ehrlich Ascites Carcinoma. An ethanolic extract showed significant anticancer activity at varying doses, increasing survival, and decreasing tumor burden. Reduced elevated levels of lipid peroxidation was attributed to a high content of phenolic compounds. (10)
• Mosquito Repellent Additive: Study showed nami (Discorea hispida) tuber crude extract added to the citronella, neem, and eucalyptus mosquito repellent product is very acceptable based on skin tolerance and overall repellency, while providing a non-irritating alternative to synthetic compounds. (12)
- Tubers contain the poisonous alkaloid dioscorine, resembling
It is a nervous system paralyzant, not a protoplasmic poison.
It has been reportedly
used in criminal poisoning.