882

12(2): Medicinal and poisonous plants 2

Acanthus L.

Sp. pl. 2: 639 (1753); Gen. pl. 2: 1090 (1876).

ACANTHACEAE

x = unknown; Acanthus ebracteatus: 2n = 44; Acanthus ilicifolius: 2n = 44, (48)

Major species Acanthus ebracteatus Vahl, Acanthus ilicifolius L.

Acanthus comprises 10—30 species, distributed mainly in the tropics and subtropics of the Old World, but also with a centre of diversity in the Mediterranean region.

In Indonesia and Malaysia, Acanthus ebracteatus and Acanthus ilicifolius are often used in the same way, mainly for the treatment of boils, and as an antiphlogistic and expectorant. In China, the plants are prescribed in hepatosplenomegaly, hepatitis, lymphoma and asthma. The tender shoots and leaves of Acanthus ilicifolius are also used as an antidote for arrow and snake poison; they are chewed and applied as a poultice on wounds. The leaves are mashed together with ginger, and put on sore legs or to treat rheumatic pains, while a porridge from the leaves and stems is taken for bowel complaints, stitches in the side, and as a purgative. In Indonesia and Thailand, the powdered seeds are taken with water for purifying the blood, or the pounded seeds are applied on infected wounds, while a few seeds act as a vermifuge, when swallowed.
Acanthus ebracteatus is commonly used in Peninsular Malaysia as a cough mixture, made from the boiled seeds. In the Philippines, Indo-China and India, a decoction of the mucilaginous leaves and roots is considered astringent, emollient and expectorant, and used on swellings, against coughs, asthma and rheumatism, and boiled in milk against leucorrhoea. In China, the roots are used to treat chronic fever.
In India, goats and cattle eat the young leaves of Acanthus ebracteatus, but only when chopped and bruised. In the Philippines, lye is prepared from the ash of the whole plant for making soap. In Thailand, a decoction of the leaves of Acanthus ilicifolius is used as a hair tonic, for wound healing and skin diseases.

Plants of both Acanthus species are generally collected from the wild for use within the region. International trade exists within the Chinese herbal medicine network, but export from South-East Asian countries is not known to exist.

Besides the well-known sterols e.g. sitosterol, stigmasterol and their glycosides, Acanthus ilicifolius contains the alkaloid 2-benzoxazolinone, which shows leishmanicidal activity in vitro. An extract of the plant also displays analgesic, anti-inflammatory and antileukaemic activity. A mosquito coil prepared with leaves of Acanthus ilicifolius shows a high activity against biting of the mosquito Aedes aegypti, but the roots do not display any larvicidal action.
The seeds of Acanthus ebracteatus contain 2(3H)-benzoxazolone. Several extracts of the aerial parts of this plant, especially those prepared by organic solvent extraction, strongly inhibit the mutagenicity of aflatoxin B1, an indirect mutagen, when tested in the presence of S-9 mix. These fractions also markedly inhibit the activity of rat liver aniline hydroxylase, an enzyme necessary for activation of indirect mutagens. An extract of the aerial parts inhibits pro-inflammatory eicosanoid synthesis in activated leucocytes. Finally, an ethanol extract of the aerial parts of Acanthus ebracteatus shows 100% mortality on larvae of the tick Boophilus microplus.

Erect or reclining shrubby herbs, mostly perennial. Leaves decussate, simple, undulate to pinnatifid, rarely entire, margins often spiny, rigid, without cystoliths, dark green and shiny; petiole present; stipules absent, but often with a pair of spines from the leaves in the stipular position. Inflorescence a terminal uninterrupted spike. Flowers bisexual, asymmetrical; bracts imbricate, ovate, large; bracteoles in 2 pairs, oblong; calyx 4-partite, lobes imbricate, 2 outer ones larger, corolla tube short, horny, upper lip absent, lower lip elongate, obtusely 3-lobed; stamens 4, slightly didynamous, filaments stout, attached to the corolla throat, anthers 1-celled, linear oblong, bearded along 1 margin; ovules 2 in each loculus, style slender, stigma 2-fid. Fruit a capsule, erect, oblong to ellipsoid. Seeds 4, orbicular, muricate, glandular. Seedling with hypogeal germination.

Growth of Acanthus ebracteatus and Acanthus ilicifolius is continuous in the sense that there are no resting terminal buds. In South-East Asia flowering and fruiting are non-seasonal. Flowers are pollinated by both sunbirds and insects. The weak protandry restricts self-pollination. Flowers usually last 2 days, only a few opened flowers are found at a time on a spike.

Acanthus is closely related to Blepharis and Crossandra, all having 1-celled anthers and 4 calyx segments. Some authors consider Acanthus ebracteatus and Acanthus ilicifolius as variations of one species. There is a lot of variation in leaf form in both species, they mostly have a sinuous dentate and spinous margin, but can also be spineless and entire. The form with entire, spineless margins has been assumed to be a separate species, Acanthus volubilis Wallich, but is here considered a synonym of Acanthus ilicifolius. This foliar variation is partly genotypic and partly phenotypic; lack of spines and undulate margins seems to be a juvenile character, but can also occur just below the inflorescence. The spininess seems to be accentuated with water stress, which is related to salinity, seasonality and light intensity.
The epidermal glands of Acanthus ilicifolius are the source of secreted salt, which gives the upper leaf surface a greasy feel.

Acanthus species from India and South-East Asia are mangrove and salt-marsh plants, very common along banks of estuaries and lagoons close to the seashore. They grow well on fine silt or mud with high salt content and high water level. Diurnal fluctuations in inundation can be tolerated but not continuous water logging.

Acanthus is propagated by seed. Release of the seed is explosive, with the capsule splitting violently, dispersing the seeds up to 2 m away. Acanthus ebracteatus and Acanthus ilicifolius grow in clumps in the wild, and division of these clumps is also a means of propagation.

Acanthus ebracteatus and Acanthus ilicifolius are normally free from diseases and pests.

Harvesting of Acanthus from the wild can be done throughout the year. When dug up for the roots, plants should be replanted with some small roots left.

Fruits of Acanthus harvested for the seeds are sold fresh in Malaysia. Fruits and roots should be dried and kept as stock.

In India, flowering phenology and pollination of Acanthus ilicifolius are being studied in order to plan regeneration and breeding programmes. With the help of molecular markers the genetic polymorphism was determined in 8 populations of Acanthus ilicifolius along the Indian coast; moderate genetic polymorphism was found between populations and low polymorphism within populations. Destructive harvesting of the plants to obtain the roots and habitat destruction are affecting the Acanthus populations.

Very little is known about the phytochemistry and pharmacology of both Acanthus species. Their activities against mosquitos and ticks are interesting, and therefore Acanthus spp. might be of some local importance in controlling them.

Chungsamarnyart, N., Jiwajinda, S., Jansawan, W., Kaewsuwan, U. & Buranasilpin, P., 1988. Effective plant crude-extracts on the tick (Boophilus microplus) I. Larvicidal action. Kasetsart Journal, Natural Sciences 22(5): 37—41.
Kapil, A., Sharma, S. & Wahidulla, S., 1994. Leishmanicidal activity of 2-benzoxazolinone from Acanthus illicifolius in vitro. Planta Medica 60(2): 187—188.
Rao, T.A., 1998. Flowering phenology and pollination of the eumangroves and their associates to plan regeneration and breeding programmes. Journal of Economic and Taxonomic Botany 22(1): 19—27.
Ridley, H.N., 1923. The flora of the Malay Peninsula. Vol. 2, Chapter 13. Acanthus. Government of the Straits Settlements and Federated Malay States. L. Reeve & Co, London, United Kingdom. pp. 577—578.
Thangam, T.S., Srinivasan, K. & Kathiresan, K., 1993. Smoke repellency and killing effect of mangrove plants against the mosquito Aedes aegypti (Linnaeus). Tropical Biomedicine 10(2): 125—128.
Tomlinson, P.B., 1986. The botany of mangroves. Cambridge University Press, Cambridge, United Kingdom, New York, United States & Melbourne Australia. pp. 173—179.

H.C. Ong

Acanthus ebracteatus
Acanthus ilicifolius

Ong, H.C., 2001. Acanthus 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:
Acanthus ebracteatus
Acanthus ilicifolius