Hedyotis (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

Hedyotis L.

Protologue: Sp. pl. 1: 101 (1753); Gen. pl. ed. 5: 44 (1754).

Family: Rubiaceae

Chromosome number: x= 8, 9, 11; H. verticillata: 2n= 32; in general polyploids

Major species

• Hedyotis auricularia L.

Origin and geographic distribution

Hedyotis occurs predominantly in the tropical and warm subtropical regions of India, South-East Asia, Australia, Micronesia, Polynesia and North America, and the number of species is estimated at up to 250 (including Oldenlandia L.).

Uses

Hedyotis is commonly applied as a poultice to heal wounds, small sores, boils and sore eyes. In Peninsular Malaysia, the Philippines and India, the leaves of H. auricularia and H. philippensis are rubbed fresh or after boiling on aching parts of the body or applied as a poultice on cracked skin as an emollient. In Peninsular Malaysia, whole plants of H. pinifolia Wallich or H. insularis (Spreng.) Deb & R.M. Dutta (synonym H. glabra R.Br.) are used for this purpose as well. In India, a decoction or extract of the leaves or the whole crushed leaves of H. auricularia are a popular medicine for diarrhoea, cholera, dysentery and other intestinal problems. In Fiji, a decoction of the leaves is taken for headache and eye problems, to stop bleeding wounds and to promote healing.

A decoction of the roots of H. philippensis or the aerial parts of H. verticillata or H. insularis are used internally for dysentery, colic, gonorrhoea and as a stomachic and externally to wash small children with stomach-ache or applied as a poultice to scalds.

In Peninsular Malaysia, the roots of H. costata (Roxb.) Kurz (synonym H. vestita R.Br. ex G. Don) are boiled to make a lotion for rheumatism. H. leucocarpa Elm. (synonym Oldenlandia rigida (Blume) O. Kuntze) is externally used in Sumatra to treat fever. The leaves of H. insularis , mixed with a little ginger and salt, are used for incipient sores, while a decoction is taken for purifying the blood.

Production and international trade

Hedyotis is only used on a local scale.

Properties

The stem and roots of H. auricularia contain an unstable alkaloid, hedyotine, and the crystalline bis-indole alkaloid auricularine. The total alkaloid content is about 0.3%. The aerial parts also contain oleanolic acid, ursolic acid, β-sitosterol and stigmasterol. An ethanolic extract showed selective antifungal activity against some important plant-pathogenic fungi using the filter paper disk diffusion technique. The extract also showed antiviral activity against the herpes simplex type-1 (HSV-1) and vesicular stomatitis (VSV) viruses in vitro.

An extract from the leaves and stem of H. verticillata showed biological activity in the brine shrimp test (LC₅₀ = 22 μM/ml) and some antibacterial tests.

Description

• Woody herbs or subshrubs, erect or procumbent.
• Leaves opposite, simple, entire; sessile or petiolate; stipules interpetiolar, adnate to base of petiole, margin with 1–-several setae.
• Inflorescence an axillary or terminal subsessile fascicle or pedunculate corymbiform cyme.
• Flowers small, 4-merous, bisexual, homostylous or heterostylous; calyx tube subglobose, lobes distinct; corolla white, tube short, not longer than calyx lobes, lobes valvate; stamens 4, normally exserted, filaments attached to corolla between the lobes, anthers dorsifixed; ovary inferior, 2-locular, ovules 5-15 on fleshy hemispherical placentas, placenta peltately attached to septum by short stalk, style filiform, normally exserted, stigma 2-fid.
• Fruit a hard capsule, splitting septicidally to the base into 2 indehiscent pyrenes or rarely dehiscent; beak mostly absent; seeds numerous.
• Seed small, depressed obconical or angular, finely reticulate.
• Seedling with epigeal germination; cotyledons very small.

Growth and development

Most Hedyotis species are found flowering throughout the year when enough moisture is available.

Other botanical information

Hedyotis and Oldenlandia are very closely related genera, with a long history of taxonomic confusion, and many species have been described with either one of them as a synonym. Recent studies tend to keep the genera separate, mainly on the basis of morphological and embryological evidence, although this is not always clear in all species concerned.

Ecology

Hedyotis is often found in sunny to shaded, marshy localities, especially on hard or stony soils along roadsides, on walls, in gardens, lawns, fallow fields, dry riverbeds, along watercourses, and as a weed in rainfed and irrigated rice fields. Some species though are primarily found in shaded forests.

Propagation and planting

Hedyotis is propagated by seed.

Harvesting

Hedyotis is harvested from the wild whenever needed.

Handling after harvest

Hedyotis is mainly used fresh.

Genetic resources and breeding

Hedyotis species are widespread and common throughout South-East Asia as weeds, and there is no risk of genetic erosion.

Prospects

Little information is available about the phytochemical and pharmacological activities of Hedyotis, or isolated compounds. More research is therefore needed to fully evaluate its possible potential.

Literature

• Aguilar, N.O. & Lemmens, R.H.M.J., 1999. Oldenlandia L. In: De Padua, L.S., Bunyapraphatsara, N. & Lemmens, R.H.M.J. (Editors): Plant Resources of South-East Asia No 12(1). Medicinal and poisonous plants 1. Backhuys Publishers, Leiden, the Netherlands. pp. 364-367.
• Ali, A.M., Mackeen, M.M., El-Sharkawy, S.H., Hamid, J.A, Ismail, N.H, Ahmad, F.B.H & Lajis, N.H., 1996. Antiviral and cytotoxic activities of some plants used in Malaysian indigenous medicine. Pertanika: 19(2-3): 129-136.
• Deb, D.B. & Dutta, R., 1983. Nomenclatural changes in Hedyotis (Rubiaceae) of South Asia. Taxon 32(2): 284-285.
• Halford, D.A., 1992. Review of the genus Oldenlandia L. (Rubiaceae) and related genera in Australia. Austrobaileya 3(4): 683-–722.
• Hamzah A.S., Lajis, N.H. & Sargent, M.V., 1994. Kaempferitrin from the leaves of Hedyotis verticillata and its biological activity. Planta Medica 60(4): 388-389.
• Quisumbing, E., 1978. Medicinal plants of the Philippines. Katha Publishing Co., Quezon City, the Philippines. pp. 908-910.

Selection of species

• Hedyotis auricularia
• Hedyotis philippensis
• Hedyotis verticillata

Authors

• Isa Ipor