Homalomena (PROSEA)
Introduction |
Homalomena Schott
- Protologue: Schott & Endl., Melet. bot.: 20 (1832).
- Family: Araceae
- Chromosome number: x= 20; H. griffithii: 2n= 40, H. sagittifolia: 2n= 40, 80
Origin and geographic distribution
Homalomena comprises about 150 species, and occurs from India, Burma (Myanmar), Indo-China and southern China, through Thailand and Malesia, to the Solomon Islands. Approximately 8 species occur in tropical America. Western Malesia is by far richest in species, with about 40 species in each of Peninsular Malaysia, Sumatra and Borneo, and 18 in Java. Towards the east the number of species is lower, with about 4 in each of the Philippines and Sulawesi, 2 in the Moluccas, but again 18 in New Guinea.
Uses
In Indonesia (Java, Kalimantan, Sulawesi, the Moluccas) the stems (often the underground part) and leaves of Homalomena are used as a poultice to treat cuts, wounds, sores and rheumatism, and a decoction of the stem and roots is used to treat syphilis and after miscarriage. The juice from old petioles is used to improve visual acuity. Similar applications are recorded from Peninsular Malaysia. Leaves are used as a poultice during childbirth, and to treat sores and lumbago. A decoction of the stem and roots is drunk to treat fever, colic and hoarseness. In New Guinea, some Homalomena species are applied in traditional medicine: leaves heated in a fire are used for rubbing to treat muscular complaints. In New Ireland, H. peekelii is used to treat malaria and headache. The leaves, stems and roots are applied in rituals in New Guinea; they are said to produce hallucinations when ingested in small amounts. The leaves are used in adornment, or as perfume. In Indonesia, pieces of the stem are placed in fish-traps as bait to catch lobsters and shrimps, and leaves are used as packing material for tobacco.
Decoctions of the stem of H. aromatica (Roxb. ex Sims) Schott and H. occulta (Lour.) Schott (which are perhaps conspecific) are used in traditional medicine in Vietnam, southern China and Thailand to treat rheumatoid arthritis. In Vietnam, infusions and ethanolic extracts of H. aromatica stems are also applied against stomach disorders and as a tonic.
Homalomena , mostly called H. lindenii (Rodigas) Ridley, is also cultivated as an ornamental in tropical gardens, and as a pot plant.
Properties
The major component of the essential oil from H. aromatica stems is linalool (up to 80%). The oil has a delicate aroma and antibacterial activity, and has been recommended in Vietnam as an ingredient of toothpaste. Furthermore, several sesquiterpenoids have been isolated from a rhizome extract of H. aromatica , whereas its rhizome showed weak antiphlogistic activity. A crude ethanol extract of H. aromatica showed larvicidal activity on the cattle tick Boophilus microplus in tests in Thailand. Significant anti-inflammatory and analgesic activities have been found for H. occulta extracts in tests in China.
Botany
- Small to large, creeping or decumbent to erect herbs, lower part of stem rhizomatous, vegetative parts usually strongly aromatic when crushed, with pungent smell of citrus, celery, parsley, liquorice, anise or ginger.
- Leaves arranged spirally, simple, deeply cordate to oblanceolate, often very variable in shape, entire, glabrous, striate-veined; petiole longer or shorter as blade, channelled to terete, with sheath at base; stipules absent.
- Inflorescence a spadix, erect at anthesis, later decumbent, enclosed by a boat-shaped, green, reddish, yellowish or white, persistent spathe.
- Flowers unisexual, densely packed; male flowers in upper part of spadix, with 2-4 stamens, filaments very short to absent, anthers usually with cap-like connective; female flowers in lower part of spadix, with superior incompletely 2-4-locular ovary, style very short or absent, stigma button-like or disk-like; male and female zone of spadix usually not separated by sterile flowers.
- Fruit a small translucent greenish berry, closely packed within the persistent and usually somewhat enlarging spathe, several-seeded.
- Seeds very small, c. 1 mm long, longitudinally ribbed, albuminous.
Homalomena is taxonomically difficult. The species are often very similar, and many show considerable infraspecific variation. The published information on uses is often not reliably reducible to species, and species names used in the literature are often incorrect.
Ecology
Homalomena occurs mainly in the understorey of lowland rain forest, but it can also be found up to the mid-montane zone. It is generally shade-loving and grows on the forest floor, often on steep soil banks (e.g. stream banks). It is also often found in swamp forest, and is sometimes rheophytic, and occasionally occurs in regrowth forest. It is absent in regions with a strongly seasonal climate.
Management H. aromatica is propagated in Vietnam by stem cuttings. Shoot cultures of ornamental Homalomena cultivars have been cultured successfully on modified Murashige and Skoog medium, as well as callus cultures of H. occulta in China.
Genetic resources
The Homalomena species treated here are all at least locally common. However, most species occur in primary lowland rain forest, and the ongoing destruction of this habitat may easily endanger them, particularly those with limited areas of distribution. In some regions, they are popular medicinal plants much collected from the wild, e.g. H. aromatica in Vietnam. This may also lead to severe genetic erosion or even extinction of wild populations.
Prospects
Homalomena is popular as a medicinal plant in many regions of tropical Asia, and often used for similar complaints. Research on its phytochemistry and pharmacological properties has been very limited up to now, but shows promising results. The antirheumatic activity in particular deserves more attention.
Literature
121, 334, 503, 671, 903, 932.
Selection of species
Authors
Harini M. Sangat