1215

12(2): Medicinal and poisonous plants 2

Oroxylum indicum (L.) Kurz

For. fl. Brit. Burma 2: 237 (1877).

BIGNONIACEAE

2n = 28, 30

Bignonia indica L. var.'ALFA'a (1753), Bignonia pentandra Lour. (1790), Calosanthes indica (L.) Blume (1826).

Midnight horror (En). Indonesia: pongporang (Sundanese), kayu lanang, mungli (Javanese). Malaysia: beka, bonglai, kulai. Philippines: pingka-pingkahan (Tagalog), abong-abong (Bisaya), kamkampilan (Iloko). Cambodia: pi ka. Laos: lin may, ung ka. Thailand: phe kaa (central), litmai (northern), lin faa (north-eastern). Vietnam: n[us]c n[as]c, ho[af]ng b[as] nam, m[ooj]c h[oof] di[eej]p.

Oroxylum indicum is found from India eastward to southern China and the Philippines, and throughout South-East Asia; in Indonesia eastward to Sulawesi and the Lesser Sunda Islands. Locally cultivated near human settlements.

Throughout its distribution area, the bitter bark is employed for intestinal complaints. It is credited with astringent and tonic properties, and widely used for diarrhoea and dysentery. In Malaysia, a decoction of the leaves is drunk for stomach-ache. Externally it is employed in cholera, fever, childbirth and rheumatic swellings. The boiled leaves are employed as a poultice during and after childbirth, and in dysentery as well as for an enlarged spleen. Leaf poultices may be further applied for toothache and headache. In Java, the pounded bark mixed with water is taken in gastritis and to purify the blood. In northern Sulawesi, the inner bark is used to arrest bleeding. In the Philippines, a decoction of the root is credited with antirheumatic, antidysenteric and diuretic properties; the leaves are used in antirheumatic baths. In Thailand, the root and root bark are used for diarrhoea and dysentery, while the stem bark is applied for ulcers and abscesses. In Vietnamese folk medicine, a decoction of the seeds is used for cough, bronchitis and gastritis. Externally the seeds are applied to ulcers. A decoction of the dried root bark or stem bark is used in the treatment of allergic diseases, urticaria, jaundice, asthma, sore throat, laryngitis, hoarseness, gastralgia, diarrhoea and dysentery. An alcoholic maceration of the fresh bark is externally applied on allergic dermatitis. In Thai folk medicine, the root is employed as a tonic and antidiarrhoeal, whereas the seed is used as a laxative and expectorant. Throughout South-East Asia, cooked flowers, buds and young pods are highly esteemed as a vegetable. In Java, flowers, young shoots and the stem bark are consumed fresh as a side dish. The wood can be used as a firewood although it is of poor quality.

Oroxylum indicum is only used at a local scale.

The various parts of Oroxylum indicum are rich in flavonoids. The leaves contain the flavonoids baicalein (5,6,7-trihydroxyflavone), scutellarein (4',5,6,7-tetrahydroxyflavone), and their glycosides baicalin (baicalein-7-glucuronide) and scutellarin (scutellarein-7-glucuronide). The stem and root bark contain e.g. baicalein, scutellarein, oroxylin A (5,7-dihydroxy-6-methoxyflavone), chrysin (5,7-dihydroxyflavone) and p-coumaric acid. Baicalein and oroxindin (wogonin-7-O-'BETA'-D-glucuronide) have been isolated from the seeds.
Other compounds mentioned in the literature include the prenylated naphthoquinone lapachol, and the anthraquinone derivative aloe-emodin.
Dichloromethane extracts of the stem bark and root of Oroxylum indicum were found to have antimicrobial activities against Gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus), Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa) and a yeast (Candida albicans). Bioassay-guided chromatographic fractionation led to the isolation of flavonoids (e.g. baicalein, chrysin and oroxylin A) and lapachol as active constituents. Lapachol was found to be active against the Gram-positive bacteria; 5 µg gave a zone of inhibition equivalent to that shown by 5 µg of streptomycin, whereas 5 µg of chrysin gave inhibition zones of equal size to that of 5 µg of streptomycin against Pseudomonas aeruginosa.
The inhibitory activity of lapachol from Oroxylum indicum root against soya bean 5-lipoxygenase (IC₅₀ 0.79 µg/ml) was equivalent to that of the positive control (the flavonoid fisetin; IC₅₀ 0.97 µg/ml), whereas 50 µg/ml of the dichloromethane extract of the root bark gave 100% inhibition of leukocyte lipoxygenase. These activities might indicate an anti-inflammatory effect for the dichloromethane extract, mainly due its lapachol content.
The isolated flavonoid baicalin also showed inhibitory effects against the human T cell leukaemia virus type 1, and the human immunodeficiency virus (HIV-1). Baicalein furthermore showed antiproliferative activity in cultured rabbit vascular muscle cells, and lipoxygenase activity in vitro. Other pharmacological activities of baicalin and baicalein include anti-inflammatory activity of baicalin in the rat adjuvant arthritis model, inhibition of LPS-induced IL-1 production by both flavonoids, and inhibition by baicalein of leukotriene C-4 biosynthesis by rat resident peritoneal macrophages. The methanol extract of the young perianth exhibited strong antitumour-promoting activity when tested against 12-O-tetradecanoylphorbol-13-acetate (TPA) induced Epstein-barr virus early antigen activation.

Baicalin, baicalein and related flavonoids also occur in Scutellaria (Labiatae). The naphthoquinone lapachol is also present in other Bignoniaceae, such as Paratecoma peroba (Record & Mell) Kuhlm. from South America and Tectona grandis L.f. (Verbenaceae).

A semi-deciduous, sparingly branched tree up to 27 m tall; trunk up to 40 cm in diameter, bark grey, with prominent leaf scars, twigs thick, pithy, later hollow, lenticellate. Leaves crowded, imparipinnate, 3—4 times pinnate, 0.5—2 m long; petiole long, rachis swollen at points of insertion; stipules absent; leaflets ovate to oblong, 4—11(—15) cm x 3—9 cm, base cuneate or mostly oblique, apex acuminate, entire, with scattered glands on the lower surface. Inflorescence an erect raceme, terminal, 25—150 cm long, peduncle and rachis partitioned. Flowers bisexual, pedicel 2—4 cm long, bracteolate; calyx coriaceous, campanulate, containing water in bud, 2—4 cm long, 1.5—2 cm in diameter, brown or dirty violet, becoming almost woody in fruit; corolla funnel-shaped, about 10 cm long, lobes 5, subequal, margin wrinkled, reddish outside, yellowish to pinkish inside; stamens 5, inserted in the throat, hairy at the base; ovary superior, 2-celled, many-ovuled. Fruit a pendent capsule, sword-shaped, 45—120 cm x 6—10 cm, valves flat, almost woody, finally black. Seed 5—9 cm x 2.5—4 cm, including the membranous and transparent wing. Seedling with epigeal germination; hypocotyl elongated; cotyledons leafy.

The terminal inflorescences of Oroxylum indicum induce a sympodial growth and the leaves are crowded near the end of the stem or branches, giving a mature tree an open irregular crown. When an inflorescence has finished flowering, the leaves below it fall off and the leafless stem is left as a pole, with a few pods dangling from its extremity. After 3—4 weeks in a leafless state, one or more lateral buds start developing into side-branches, and the cycle can be repeated. Its architecture represents Chamberlains=s model. Branches on the same tree may flower, fruit or produce new shoots independently. Trees can be found flowering and fruiting throughout the year. In some areas a peak in flowering is observed at the beginning of the dry season, whereas fruits are present on trees in a leafless state during the dry season. The flowers are nocturnal and 1—2 flowers open in the course of one night; before sunrise the corolla falls off. They are pollinated by bats attracted by the foetid smell. The winged seeds are wind-dispersed as the pods open.

Oroxylum is a small genus and a second species, Oroxylum flavum Rehder, has been described based on a specimen raised from seed collected in southern China.

Oroxylum indicum is a short-lived nomad tree, nowhere gregarious, always encountered in canopy openings, secondary growth and thickets. It tolerates a wide range of both climatic and soil conditions, and occurs mostly below 1000 m altitude.

Oroxylum indicum can be propagated by seed or stem cuttings. As opened fruits will have lost part of their seeds and seed may be affected by fungal attack, seed should collected from closed fruits. Seed germination is about 50% in 19—25 days. Germination success is enhanced by soaking for 24 h prior to sowing and planting at 0.5 cm depth.

Seed from ripe fruits, stem bark and root bark of Oroxylum indicum are collected all year round.

Stem bark and root bark of Oroxylum indicum are generally dried prior to use.

Oroxylum indicum is widespread and common in disturbed habitats throughout South-East Asia, and therefore not endangered. There are no known breeding programmes of Oroxylum indicum.

The flavonoids and lapachol isolated from Oroxylum indicum show interesting pharmacological activities in the fields of virus-inhibition and anti-inflammatory activity. These merit further research in order to evaluate their possibilities and potential for future medicine.

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M.A. Rasadah

Rasadah, M.A., 2001. Oroxylum indicum (L.) Kurz. 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