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12(2): Medicinal and poisonous plants 2

Gmelina L.

Sp. pl. 2: 626 (1753); Gen pl. ed. 5: 274 (1754).

VERBENACEAE

x = 19; Gmelina arborea: 2n = 36, 38, Gmelina asiatica: 2n = 38, 40, Gmelina philippensis: 2n = 38

Major species Gmelina asiatica L., Gmelina elliptica J.E. Smith, Gmelina philippensis Cham.

Malaysia: bulang, bulangan.

Gmelina consists of about 33 species of trees and shrubs and is distributed from Pakistan and India, Sri Lanka and southern China through the Malesian Archipelago towards northern and western Australia, Fiji, New Zealand and New Caledonia. About 12 species occur in Malesia. Gmelina arborea Roxb. is the best-known species of the genus. It has frequently been planted as a fast-growing plantation tree in South-East Asia as well as in India, tropical Africa and Brazil.

The uses of the various medicinally important Gmelina appear to be mutually exchangeable. Some confusion exists on the specific identity of a particular use in some regions. The uses can be largely described as demulcent, purgative and diuretic, and the plants are also applied in rheumatic affections. Furthermore, it is primarily externally applied as a rubefacient and counterirritant. In the Moluccas, sap of the inner bark of Gmelina moluccana (Blume) Backer ex K. Heyne is externally applied to cleanse wounds and ulcers. Roots, leaf sap and flowers of Gmelina arborea are used in Indian traditional systems of medicine in the form of a decoction as an anodyne, diuretic, laxative, for loosening phlegm, as an appetite stimulant and a galactagogue, and for the treatment of liver disorders. In Thailand, the roots of Gmelina are applied externally on wounds and abscesses. Several species are used as a hedge plant, and the leaves are used as cattle fodder.

Gmelina is only used on a local scale.

From the leaves of Gmelina arborea several monoacylated, diacylated, and triacylated iridoid glycosides have been isolated. These include 6-O-'ALFA'-L-rhamnopyranosylcatalpol, 6-O-(3''-O-trans-feruloyl)-'ALFA'-L-rhamnopyranosylcatalpol, 6-O-(2''-O-acetyl-3'',4''-O-di-trans-cinnamoyl)-'ALFA'-L-rhamnopyranosylcatalpol, 12 acylated iridoid glycosides named gmelinosides A—L, and the related phenylpropanoid glycosides verbascoside (acteoside) and martynoside. A similar range of rhamnopyranosylcatalpol esters and related compounds is present in the leaves of Gmelina philippensis. Furthermore, the leaves of Gmelina arborea contain glycosides of the flavonoids luteolin, apigenin and quercetin, and the presence of several lignans (including arboreol, isoarboreol, methyl arboreol, arborone, gmelanone, gummadiol, and 7-oxodihydrogmelinol) in the heartwood is reported in the literature.
In the field of biological activities, an ethanol extract of the stem of Gmelina arborea showed antiplasmodial activity against Plasmodium falciparum (IC₅₀ 36 µg/ml) and a 59—85% inhibition at 50—100 µg/ml.
In addition, hexane- and chloroform-soluble extracts of Gmelina asiatica roots exhibited prominent oral antipyretic activity in rabbits receiving subcutaneous yeast injections. Furthermore, carrageenan-induced rat paw oedema (acute inflammation) and cotton pellet granuloma (chronic inflammation) methods have been used to test the anti-inflammatory effect of Gmelina asiatica root powder in male albino rats. A reduction was observed in both acute and chronic inflammation. Gmelina asiatica also reduced the lipid peroxide content of granuloma exudate and liver, and 'GAMMA'-glutamyl transpeptidase in the granuloma. Serum albumin in granuloma was normalized. Gmelina asiatica also normalized the increased levels of serum acid and alkaline phosphatase. Therefore it was concluded that the crude drug may exert anti-inflammatory activity through antiproliferative, anti-oxidative and lysosomal membrane stabilisation.

The isolation of monoacyl, diacyl, and triacyl derivatives of 6-O-'ALFA'-L-rhamnopyranosylcatalpol has been reported for several plant families including the Buddlejaceae, Scrophulariaceae, and Verbenaceae (e.g. Premna).

Shrubs or small to medium-sized trees, up to 30(—40) m tall, with cylindrical bole having a diameter of up to 100(—250) cm, without buttresses but sometimes flanged; bark smooth or scaly, pale brown to grey; twigs glabrous or pubescent, spinous or unarmed. Leaves opposite, simple, entire, toothed or lobed, often strongly varying in shape within the same plant, reticulately veined; petiolate; stipules absent. Inflorescence a terminal or axillary cymose, raceme or panicle. Flowers zygomorphic, bisexual, with small bracts; calyx tubular or somewhat campanulate, with 4—5 teeth or subentire, generally with large glands; corolla with (4—)5 fused petals, tube slender below, ventricose upwards, more or less 2-lipped, hairy outside, yellow to orange or purplish; stamens 4, didynamous, alternate with the corolla-lobes, inserted in the lower part of the corolla-tube, filaments flat, filiform, often sparsely glandular, anthers 2-celled, dorsifixed, elliptical to oblong; ovary 4-locular, with one ovule in each cell, ovule attached to an axile placenta at or above the middle, style filiform, with two unequal stigmatic lobes. Fruit a succulent drupe, with hard and stony endocarp, usually 4-celled. Seed oblong. Seedling with epigeal germination; cotyledons somewhat fleshy.

Trees of Gmelina arborea are deciduous, shedding their leaves around January—February in all areas where they are planted. Flowering occurs when new leaves have just begun to develop (March—April). Trees 3—4 years old are able to flower and fruit regularly. The fruit matures within 2—3 months. Other Gmelina have been found to flower and fruit in almost every month of the year.
Gmelina arborea and Gmelina asiatica are self-incompatible and obligately outcrossing. The bilaterally symmetrical flowers with deep-seated nectar are manipulated and pollinated by large-bodied carpenter bees (Xylocopa).

The genus Gmelina is closely related to the large genus Vitex, from which it is distinguished by its large and usually broadly bell-shaped corolla-tubes, and the well-shaped bole. In Vitex the corolla-tube is short and cylindrical, and the bole is usually poorly shaped.

Gmelina is frequently found in primary or secondary, more open forests, along streams and on ridges. It usually prefers well-drained, moist soils and occurs from sea-level up to 1200 m altitude. Most species appear to be pioneer species, and may regenerate gregariously.

Gmelina is usually propagated by seed. At present direct sowing is preferred. However, planting of stumps is still widely practised. Vegetative propagation from stem cuttings using various hormone preparations is also successful. Germination of Gmelina arborea occurs 7—15 days after sowing and amounts to about 80%. Trials for Gmelina elliptica show poor and slow germination. The depth of the root system in Gmelina arborea varies. Growth is very rapid during the first 6 years, but decreases sharply from the 7th year onwards. Growth is strongly site-dependent.

For ornamental purposes Gmelina philippensis is usually severely pruned to maintain a balanced shape.

Gmelina asiatica is often parasitized by Dendrophtoe falcata (L.f.) Ettingsh. (Loranthaceae) and suffers seriously from powdery mildew (Sphaerotheca verbenae) in India.

In general Gmelina is harvested whenever the need arises. Leaves, flowers and fruits are in general present throughout the year.

Plant parts of Gmelina are usually used fresh but roots and leaves may well be dried for future use.

The various species of Gmelina are usually widely distributed, and although they are not abundant (except on favourable sites), none of them seems to be threatened with extinction.

Although Gmelina species are known to be rich sources of iridoids, and iridoids as a class of natural compounds are known to display a variety of biological effects (e.g. in the field of anti-inflammation, and on the central nervous system). Not much pharmacological information is available for the specific compounds found in the species treated.

Helfrich, E. & Rimpler, H., 2000. Iridoid glycosides from Gmelina philippensis. Phytochemistry 54(2): 191—199.
Hosny, M. & Rosazza, J.P.N., 1998. Gmelinosides A—L., 12 acylated iridoid glycosides from Gmelina arborea. Journal of Natural Products 61(6): 734—742.
Ismail, T.S., Gopalakrishnan, S. & Begum, V.H., 1997. Biochemical modes of action of Gmelina asiatica in inflammation. Indian Journal of Pharmacology 29(5): 306—309.
Munir, A.A., 1984. A taxonomic revision of the genus Gmelina L. (Verbenaceae) in Australia. Journal of the Adelaide Botanical Garden 7: 91—116.
Perry, L.M., 1980. Medicinal plants of East and Southeast Asia. Attributed properties and uses. MIT Press, Cambridge, Massachusetts, United States & London, United Kingdom. pp. 427—428.
Simonsen, H.T., Nordskjold, J.B., Smitt, U.W., Nyman, U., Palpu, P., Joshi, P. & Varughese, G., 2001. In vitro screening of Indian medicinal plants for antiplasmodial activity. Journal of Ethnopharmacology 74: 195—204.

R.C.K. Chung

Gmelina asiatica
Gmelina elliptica
Gmelina philippensis

Chung, R.C.K., 2001. Gmelina L.. In: van Valkenburg, J.L.C.H. and Bunyapraphatsara, N. (Editors): Plant Resources of South-East Asia No 12(2): Medicinal and poisonous plants 2. PROSEA Foundation, Bogor, Indonesia. Database record: prota4u.org/prosea

The following species in this genus are important in this commodity group and are treated separatedly in this database:
Gmelina asiatica
Gmelina elliptica
Gmelina philippensis