Smilax (PROSEA)

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Plant Resources of South-East Asia
Introduction
List of species


Smilax L.

Protologue: Sp. pl. 2: 1028 (1753); Gen. pl. ed. 5: 455 (1754).
Family: Smilacaceae
Chromosome number: x= 16; S. bracteata: 2n= 32, S. china: 2n= 30, 60, 90, S. leucophylla: 2n= 32, S. zeylanica: 2n= 32

Major species

  • Smilax china L.,
  • S. glabra Wallich ex Roxb.,
  • S. leucophylla Blume.

Vernacular names

  • Indonesia: gadung cina
  • Malaysia: akar gadong
  • Philippines: sarsaparilla, banag
  • Cambodia: voë pâprâ:hs
  • Laos: khua:ng
  • Thailand: khueang
  • Vietnam: dây kim cang.

Origin and geographic distribution

Smilax contains approximately 200 species which are distributed in tropical and subtropical regions, with some herbaceous species extending their range into the temperate regions of North America, Europe and Asia.

The greatest diversity is found in eastern Asia. In Indo-China 27 species have been found, in Thailand 24 species, and the number of species is probably slightly less in Malesia.

Uses

In South-East Asia, decoctions of Smilax roots and rhizomes are rather commonly used internally to treat syphilis, gonorrhoea, rheumatism and coughs and as a tonic (e.g. after childbirth) and aphrodisiac, and externally to treat skin diseases including psoriasis, wounds, inflammations, swellings, ulcers and boils. Leaf tops have been reported to be eaten with food as contraceptive in Papua New Guinea. A decoction of the leaves is used as a purgative to expel worms and reduce swelling of the stomach in the Central Province in Papua New Guinea. The rhizomes of S. calophylla and S. myosotiflora are reputed to be used in Peninsular Malaysia as an aphrodisiac. Smilax species, particularly S. china, are used in anticancer drugs in Chinese medicine, and have been reputed to be effective as diuretic and anti-inflammatory agents. A decoction of S. glabra rhizomes is used in China in orally administered mixtures of medicinal plants for the treatment of psoriasis, and in Vietnam as an antiphlogistic to treat rheumatic arthritis, psoriasis and inflammations, and as a tonic. In Australia, an infusion of the leaves of S. australis R.Br. and S. glycophylla Smith has been used medicinally. In Guatemala and other Central American and West Indian countries, S. regelii Killip & C. Morton ("Honduras-sarsaparilla") and S. officinalis Kunth are used to treat dermatophyte infections and rheumatism. S. aristolochiifolia Miller from Mexico, known as "Veracruz-sarsaparilla", is reputed as a diuretic, increasing both volume and chloride and uric acid concentration of the urine. S. papyracea Duhamel from Mexico, Brazil and Guyana is also known as "sarsaparilla". In Saudi Arabia S. sarsaparilla L. is used for the treatment of rheumatism, arthritis, gout and other forms of inflammation. The roots of S. zeylanica and S. wightii A.DC. are used medicinally in India against amongst others, rheumatism, urinary complaints and venereal diseases.

Thickened roots of S. china can be used as bait for subterranean termites, in conjunction with insecticides. The stems are sometimes used as cane to make baskets. The edible but acid fruits of S. macrocarpa Blume are commonly collected from the wild in Java, eaten fresh, as an ingredient of fruit salad or preserved in syrup. Young shoots and leaves of S. leucophylla and rhizomes of S. megacarpa are edible.

Production and international trade

The rhizomes of some Smilax spp. are much sought after and are exported in fairly large quantities; for example, rhizomes of S. glabra in Laos. Roots of S. china and S. glabra are mainly imported from China and sold as herbal medicine in Chinese pharmacies throughout South-East Asia.

Properties

Roots and rhizomes of Smilax species are a well known source of steroidal saponins (1-3%): mainly glycosides of the furostanol and spirostanol aglycones sarsapogenin, smilagenin, tigogenin, neotigogenin, diosgenin and yamogenin. In the plant, the bisdesmosidic glycoside form of these aglycones seems to be the genuine component. Several steroidal saponins have been isolated from S. china rhizomes; they include dioscin, protodioscin, methylprotodioscin, gracillin and methylprotogracillin. The aglycones of these saponins are of great industrial interest as starting material for steroid hormone semisynthesis in the production of corticosteroids and sex hormones (androgens, oral contraceptives). The spirostanol saponins dioscin and gracillin are reported to have antimutagenic activity, but their similar furostanol glycosides have not shown this activity. Hot water extract of S. china shows histamine release inhibition and cytotoxic activities. Methanol extract brings about uterine relaxation and decreases barbiturate sleeping time.

The flavonoids astilbin, taxifolin and engeletin have been isolated from the dried rhizomes of S. glabra, together with some organic acids (ferulic acid, 3-0-caffeoylshikimic acid) and β-sitosterol. Quercetin and kaempferol were isolated from leaf extracts of the same plant after acid hydrolysis. A methanol extract of S. glabra rhizomes showed hypoglycaemic effects in normal and diabetic mice. S. glabra extracts showed anthelmintic activity against the trematode Clonorchis sinensis. The extracts also exhibit antiviral and anti-inflammatory activities. Extracts of S. china have been demonstrated to inhibit the mutagenicity of benzo(a)pyrene completely. Tests in Saudi Arabia showed significant inhibition of carrageenan-induced inflammation in rats when an oral dose of 500 mg/kg of S. sarsaparilla extract was applied; this extract also inhibited cotton pellet-induced exudation. In tests in Guatemala, extracts of S. lundellii Killip & C. Morton showed activity against Candida albicans, a parasitic imperfect fungus causing thrush.

In tests in China, a mixture of medicinal plants including a decoction of S. glabra rhizomes showed a lower relapse rate and longer remission in comparison with aminopterin therapy and the topical application of psoriasin to treat psoriasis.

Adulterations and substitutes

The nodular growths found on the roots of fir (Abies) trees and produced by a fungus, and similar growths on Liquidambar roots are sometimes sold as a substitute for China root (from S. china). Saponins of the same type are found in various Yucca species; other sapogenins which are interesting as starting material for steroid hormone semisynthesis include diosgenin from Dioscorea spp. and hecogenin from Agave spp.

Description

  • Dioecious climbers up to 20 m long with woody or herbaceous stems up to 12 mm in diameter, or becoming shrubby with suberect stems; stem and branches often prickly; rhizome and/or roots often thickened.
  • Leaves alternate, simple and entire, mostly ovate-orbicular, ovate to lanceolate, with 3-7 veins connected by reticulate lateral veinlets; petiole sheathing in lower part with a pair of wings, often with tendrils arising immediately above the apex of the sheath.
  • Inflorescence an axillary umbel or an umbellate raceme whose main axis bears a prophyll at the base.
  • Flowers unisexual, small, usually greenish or greenish-white; perianth with 6 free, usually recurved or patent tepals, inner tepals much narrower than outer ones; male flowers with 6(-18) free or almost connate stamens having unilocular anthers; female flowers with a superior, 3-locular ovary, style very short and with 3 elongate, recurved stigmas, 3-6 needle-like staminodes present.
  • Fruit a globose berry, usually containing 1-2 seeds.

Growth and development

In Java, most Smilax spp. flower in the period from April to September and sometimes also January-February. Pollination is by insects.

Other botanical information

Smilax has often been treated as a genus of the family Liliaceae, but is nowadays considered as a separate family Smilacaceae, together with Heterosmilax, which differs in its connate perianth segments and 3 stamens (rarely up to 12) and occurs from India to Japan, and Rhipogonum, which differs by not having sheaths and tendrils on the petioles, or bilocular anthers, and occurs in New Guinea, Australia and New Zealand. Chromosome features support the removal from the Liliaceous assemblage.

Ecology

Smilax species are often common climbers in evergreen lowland and lower montane forest up to 2400 m altitude. Several species are frequently found in scrub vegetation, open forest and shrub savanna, often on stony soils.

Propagation and planting

Tests with seed of the Australian S. australis showed a germination rate of only 10-20% after 12 months. Adventitious roots are formed in some species (e.g. S. zeylanica), which might enhance modes of vegetative propagation. Cuttings are a successful method of propagation. Mature 3-leaved stem sections treated with rooting powder and placed in pots with 10 cm diameter sealed in plastic bags and with a 1:1 sand/peat mixture showed callus tissue formation in the leaf axils within one month, when kept at 25°C and in 70% shade. The aerial calli developed roots and shoot buds after a further 3-4 weeks, and about 60% of the cuttings established successfully.

Harvesting

In China, the tuberous rhizomes of S. china are dug out and dried for the market.

Handling after harvest

In China, the rhizomes are often peeled after drying. Usually the crude drug is extracted with boiling water for 2 hours, to prepare the drug for oral application.

Genetic resources and breeding

Those Smilax spp. that are generally used medicinally are widespread and common and seem not to be easily endangered. Despite the multiple uses, no serious attempts have been made either to conserve the genetic variation, or to domesticate these species.

Prospects

The medicinal uses of Smilax are more or less the same world-wide, which may indicate a certain consensus on activity of the drug. Smilax has good prospects as starting material for steroid hormone semisynthesis. Research on properties has been carried out mainly on Chinese and Japanese Smilax species, but little is known about those found in Malesia. The taxonomy of Malesian species is also very incompletely investigated, and this hampers the interpretation of findings in literature.

Literature

  • Chang, C.L., Huang, C.Y., Yao, Y.C., Ch'ien, W.Y. & Chao, P.N., 1974. 200 cases of psoriasis treated with traditional Chinese medicine. Chinese Medical Journal 4: 205-207.
  • Chien, N.Q. & Adam, G., 1979. Über die Inhaltstoffe von Smilax glabra Roxb. [The constituents of Smilax glabra Roxb.]. Pharmazie 34(12): 841-843.
  • Koyama, T., 1975. Smilacaceae. In: Smitinand, T. & Larsen, K. (Editors): Flora of Thailand. Vol. 2. The Forest Herbarium, Royal Forest Department, Bangkok, Thailand. pp. 211-250.
  • Koyama, T., 1983. Smilacaceae. In: Tirel, C. (Editor): Flore du Cambodge, du Laos et du Viêtnam. Vol. 20. Muséum National d'Histoire Naturelle, Paris, France. pp. 69-124.
  • Lee, H. & Lin, J.Y., 1988. Antimutagenic activity of extracts from anticancer drugs in Chinese medicine. Mutation Research 204(2): 229-234.
  • Quisumbing, E., 1978. Medicinal plants of the Philippines. Katha Publishing Co., Quezon City, the Philippines. pp. 168-170.
  • Rhee, J.K., Woo, K.J., Baek, B.K. & Ahn, B.J., 1982. Screening of the wormicidal Chinese raw drugs on Clonorchis sinensis. American Journal of Chinese Medicine 9(4): 277-284.
  • Sashida, Y., Kubo, S., Mimaki, Y., Nikaido, T. & Ohmoto, T., 1992. Steroidal saponins from Smilax riparia and S. china. Phytochemistry 31(7): 2439-2443.
  • Ungson, L.B. & Sastrapradja, S., 1976. Variation in Smilax species of Java. Biotrop Bulletin No 12. 24 pp.
  • Yi, Y.J., Cao, Z.Z., Yang, W.H., Hong, W.Q., Cao, Y. & Leng, Z.K., 1995. Chemical studies of Smilax glabra (III). Isolation and identification of smiglanin from Smilax glabra. Acta Pharmaceutica Sinica 30(9): 718-720.

Selection of species

Authors

  • Stephen P. Teo
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