Rhinacanthus nasutus (PROSEA)

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Plant Resources of South-East Asia
Introduction
List of species


Rhinacanthus nasutus (L.) Kurz


Protologue: Journ. Asiat. Soc. Bengal 39, pt. 2, Nat. Hist.: 79 (1870).
Family: Acanthaceae
Chromosome number: 2n= 30

Synonyms

Rhinacanthus communis Nees (1832).

Vernacular names

  • Indonesia: daun burung (Malay, Ambon), tarebak (Sundanese), tereba jepang (Malay, Jakarta)
  • Philippines: parajito (Spanish), ibon-ibonan, tagak-tagak (Tagalog). Burma (Myanmar): anitia
  • Laos: thong kan2sang
  • Thailand: thong khan chang, thong phan chang, yaa man kai (central)
  • Vietnam: bạch hạc, kiến cò.

Origin and geographic distribution

R. nasutus is probably native to Sri Lanka, India, Indo-China and southern China, but has been introduced long ago in Madagascar, tropical East Africa, Thailand and the Malesian region (Peninsular Malaysia, Java, the Moluccas, the Philippines) where it is now widely naturalized and often common.

Uses

The roots and leaves of R. nasutus are applied externally as a remedy for certain skin disorders such as ringworm, eczema, scurf and herpes. They are either soaked in vinegar or alcohol, pounded with lemon or tamarind, or made into a decoction. In Peninsular Malaysia, they are prepared with sulphur and benzoin or vaseline. In Thailand the leaves may be pounded with alcohol, lemon and tamarind juice. The resulting extract is applied on the infected skin. In Vietnam, an infusion of R. nasutus has a reputation in folk medicine for the treatment of hypertension. In China, the stem and leaves are also applied to treat ringworm infections, as well as in early stages of tuberculosis. When applied internally the leaf is used as an antipyretic, antihypertensive, anti-inflammatory and detoxicant, and against snake venom. R. nasutus is considered to be aphrodisiac. In Thailand, anti-cancer activity has been reported.

R. nasutus is also regularly planted as a hedge plant and has been applied for erosion control in road construction. Moreover, in Thailand it is planted for its ornamental value. In Madagascar, the seeds are used for scenting clothes.

Production and international trade

The roots of R. nasutus used to be imported in Europe from China under the name "tong pamg chong".

Properties

R. nasutus is reported to contain several naphthoquinones: rhinacanthin-A and -B have been isolated from roots collected in Thailand. Bioassay-directed fractionation showed significant cytotoxicity for the latter compound in the Kenacid Blue (KB) cell line with ED50values of 3 μg/ml. The naphthoquinones rhinacanthin-C and -D, isolated from the aerial parts, exhibited potent inhibitory activity against human and murine strains of human cytomegalovirus (CMV) in vitro (ED50values of 0.02 and 0.22 μg/ml, respectively). Several other naphthoquinones have been isolated. Most of these showed significant cytotoxicity, particularly rhinacanthin-D, -H, -K, -M and -Q, whereas they also showed inhibition of rabbit platelet aggregation.

From the methanol extract of stems and leaves of R. nasutus collected in south-eastern Thailand, an antifungal naphthoquinone was isolated with an ED50value of 0.4 ppm on spore germination of Pyricularia oryzae (causing rice blast disease) and with 82% inhibition at 100 ppm. Originally the chemical structure of this naphthoquinone was thought to be 3,4-dihydro-3,3-dimethyl-2H-naphtho[2,3-b]pyran-5,10-dione, a p-quinone, which is very similar to the structures of the rhinacanthins. Recently however, this structure was revised into 3,4-dihydro-3,3-dimethyl-2H-naphtho[1,2-b]pyran-5,6-dione, an o-quinone, also known as rhinacanthone.

Furthermore, two lignans, rhinacanthin-E and -F isolated from the aerial parts, exhibited significant antiviral activity against influenza virus type A.

A 95% alcohol extract of the aerial parts exhibited antimicrobial activity against Staphylococcus aureus at a dose of 100 mg/disk. The chloroform and alcohol extracts of aerial parts show antifungal activity against Epidermophyton floccosum , Microsporum gypseum and Trichophyton rubrum . The crude ethanol extract proved to possess relatively high acaricidal activity (71-85% mortality) tested in vitro on cattle ticks.

The aqueous extract of R. nasutus has a high anti-alkylating effect against ethyl methane sulphonate; anti-alkylating substances are associated with anti-carcinogenic activity.

Finally, phytochemical investigations have furthermore revealed the presence of flavonoids (lupeol) and phytosterols (β-sitosterol, stigmasterol and their glucosides).

Description

An erect, branched shrub up to 2(-3) m tall; stems obtusely quadrangular, puberulent when young. Leaves opposite, simple, ovate to lanceolate or elliptical, 3-10 cm × 1-5 cm, base acute to attenuate, margin entire, apex acute, puberulent; petiole 0.5-2 cm long; stipules absent. Inflorescence an axillary, peduncled, lax cyme often combined into a leafy, terminal panicle, densely appressed pubescent. Flowers subsessile; calyx with 5 narrow lobes which are shortly connate at base, 5-6 mm long; corolla 2-lipped, tube narrowly cylindrical, green, upper lip with 2 teeth, 8-10 mm × 2-3 mm, white, lower lip with 3 large lobes, the central one 10-14 mm × 9-13 mm, white with red markings at base; stamens 2, inserted near the corolla tube apex, anther cells inserted at unequal level; disk present; ovary superior, 2-locular with 2 ovules in each cell, style 1, with a 2-fid stigma. Fruit a clavate, loculicidal, puberulous capsule, 17-25 mm long, basal part sterile. Seeds held up on well-developed hooks (retinacula), orbicular, flat, pubescent.

Growth and development

In Java R. nasutus flowers throughout the year, but in the Philippines it flowers only in December-March. Pollination is by insects. Fruits apparently do not ripen in Java. The seeds are ejected from the capsule by the retinacula.

Other botanical information

Rhinacanthus comprises about 10-15 species. It belongs to the tribe Justicieae of the subfamily Acanthoideae .

Ecology

R. nasutus is found in thickets, hedges and waste places up to 750 m altitude. It thrives best on moist, well-drained soils, but it is also found in much drier habitats such as rock crevices.

Propagation and planting

R. nasutus can easily be propagated by stem cuttings. Cuttings of about 10 cm, comprising 2-3 nodes, are planted under partial shade during the rainy season. Propagation by in vitro culture is another option. To obtain complete callus initiation and highest callus production in stem explants of R. nasutus , the Murashige and Skoog basal medium should be supplemented with the growth regulators 2,4-dichlorophenoxyacetic acid (2,4-D; 1.0 mg/l) and kinetin (1.0 mg/l).

Harvesting

Mature leaves are hand picked when required, preferably shortly before flowering.

Yield

Rhinacanthone has antifungal properties but occurs only at low concentration in R. nasutus . Methyl 1-methoxy-2-naphthoate is one of several precursors also isolated from R. nasutus . This precursor can easily be transformed to rhinacanthone, thereby increasing the yield to 30%.

Prospects

The naphthoquinones and lignans from R. nasutus display some very interesting effects, e.g. cytotoxic, antifungal or antiviral, which merit further attention.

Literature

  • Achararit, C., Panyayong, W. & Ruchatakomut, E., 1983. Inhibitory action of some Thai herbs to fungi. Undergraduate Special Project Report 1983. Faculty of Pharmacy, Mahidol University, Bangkok, Thailand. 13 pp.
  • Farnsworth, N.R. & Bunyapraphatsara, N., 1992. Thai medicinal plants. Prachachon Co. Ltd., Bangkok, Thailand. pp. 216-217.
  • Greshoff, M., 1894. Schetsen nuttige Indische planten [Sketches of useful Indonesian plants]. Series 1 (1-50). Extra Bulletin van het Koloniaal Museum. J.H. De Bussy, Amsterdam, the Netherlands. pp. 41-42.
  • Kernan, M.R. et al., 1997. Two new lignans with activity against influenza virus from the medicinal plant Rhinacanthus nasutus. Journal of Natural Products 60(6): 635-637.
  • Kodama, O., Ichikawa, H., Akatsuka, T., Santisopasri, V., Kato, A. & Hayashi, Y., 1993. Isolation and identification of an antifungal naphthopyran derivative from Rhinacanthus nasutus. Journal of Natural Products 56(2): 292-294.
  • Kuwahara, S., Nemot, A. & Hirmatsu, A., 1991. Synthesis of an antifungal naphthopyran derivative isolated from Rhinacanthus nasutus, Acanthaceae. Agricultural and Biological Chemistry 55(11): 2909-2912.
  • Nguyen Van Duong, 1993. Medicinal plants of Vietnam, Cambodia and Laos. Mekong Printing, Santa Ana, California, United States. pp. 35-36.
  • Sendl, A. et al., 1996. Two new naphthoquinones with antiviral activity from Rhinacanthus nasutus. Journal of Natural Products 59(8): 808-811.
  • Sinchaisri, P., 1989. Phon khong suan sakat khong phut totan mateng thimi, to alkylating activity khong ethyl methane sulphonate [Effects of solvent fractions of some anti-carcinogenic plants on the alkylating activity of ethyl methane sulphonate]. Warasan Wicha kan kaset 7(1-3): 27-33.
  • Wu, T.S., Tien, H.J., Yeh, M.Y. & Lee, K.H., 1988. Isolation and cytotoxicity of rhinacanthin A and B, two naphthoquinones from Rhinacanthus nasutus. Phytochemistry 27(12): 3787-3788.

Other selected sources

88, 97, 142, 190, 202, 287, 350, 580, 741, 801, 921, 933, 1126, 1128, 1178, 1287, 1380, 1508, 1525, 1530, 1600.


Authors

Wongsatit Chuakul, Noppamas Soonthornchareonnon & Promjit Saralamp