1165

12(2): Medicinal and poisonous plants 2

Limnophila R.Br.

Prodr.: 442 (1810).

SCROPHULARIACEAE

x = 17, 34; Limnophila aromatica: 2n = 34, 68, Limnophila indica: 2n = 34, 68, Limnophila repens: 2n = 68, Limnophila rugosa: 2n = 34

Major species Limnophila aromatica (Lamk) Merr., Limnophila indica (L.) Druce.

Limnophila consists of 35—37 species from the Old World tropics and subtropics, with tropical Asia as its centre of distribution. Limnophila indica is most widely distributed, throughout the range of the genus. About 15 species occur in South-East Asia, some of them are endemic, and 6 species are endemic to Africa. Limnophila sessiliflora (Vahl) Blume has escaped from cultivation in southern North America.

In Malaysia, the more strongly aromatic Limnophila are considered medicinal, rather than a condiment. The smell is agreeable and resembles that of turpentine, or a mixture of cinnamon and cloves or cinnamon and citrus. In Indonesia and Peninsular Malaysia, the sap of the leaves of Limnophila aromatica is used to clean wounds and sores on the legs although it is considered rather strong. A decoction of the leaves is given in fevers but also to promote appetite, and as an expectorant to clear mucus from the bronchial tubes. In India and Thailand, the plant is used as a cooling agent in fevers, and given to nursing mothers as a galactagogue. In Vietnam, the whole plant is used for its diuretic and anti-spasmodic action, against gravel in the kidneys, as a disinfectant for wounds and for haematuria; also for cough, snakebite and skin diseases. In China, the plant is used for the treatment of intoxication, body pains and for menstrual problems. In Malaysia and Indonesia, Limnophila erecta has the same medicinal uses as Limnophila aromatica. In the Philippines, an infusion of the leaves of Limnophila indica is used for dysentery and dyspepsia. In India, the plant is considered antiseptic, and the juice is rubbed on the body for strong fevers. A liniment is made from the plant with coconut oil and used in elephantiasis. Internally, the juice is given in dysentery, combined with cumin (Cuminum cyminum L.) and other aromatic plants. In Indonesia, a decoction of Limnophila rugosa is used externally to cure itching eyes, and internally for mild gonorrhoea and impotence.
In Indo-China, Thailand and Indonesia, Limnophila aromatica, Limnophila erecta, Limnophila indica and Limnophila rugosa are also eaten as a condiment or sidedish, raw, steamed or cooked. Limnophila aromatica is thought to calm the stomach after eating durian (Durio zibethinus Murray). Limnophila aromatica can also be grown as an ornamental, because of its attractive flowers.

Limnophila is traded on a local scale only, and is found fresh in markets, or dried in Chinese herbalists stores.

Limnophila aromatica contains 0.13% essential oil, the terpenes 'DELTA'-limonene and 'DELTA'-perillaldehyde being important constituents. The bactericidal activities of this essential oil against Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus were similar to those of a streptomycin and chloramphenicol reference. The activities of the essential oil against Aspergillus niger, Candida albicans and Rhizopus oryzae, however, were more marked than those of griseofulvin as reference. Phytochemical analysis also showed the presence of 2 flavonoids, nevadensin (= 5,7-dihydroxy-6,8,4'-trimethoxyflavone) and salvigenin (= 5-hydroxy-6,7,4'-trimethoxy flavone) as well as 2 phenolics, caffeic acid and chlorogenic acid. The related (methylenedioxy type) flavonoid 5-hydroxy-6,8-dimethoxy-3',4'-methylenedioxyflavone has also been isolated from Limnophila indica.
The essential oil of Limnophila rugosa contains linalool (0.1%), estragole (22%), cis-anethole (0.03%), anisaldehyde (0.05%), trans- anethole (75%), anisyl acetone (0.03%), caryophyllene (0.08%), humulene (0.15%) and 'ALFA'-bulnesene (0.01%). Also the compounds 3'BETA'-hydroxy-20(29)-en-27-oic acid, nevadensin, and demethoxysudachitin were isolated. The flavonoid nevadensin, administered intravenously (3.1 mg/kg), exhibited a hypotensive effect on both normotensive and spontaneous hypertensive rats under pentobarbital anaesthetization. After administration of nevadensin, the mean arterial pressure decreased by about 50 mm Hg for 30 minutes.
The essential oil of Limnophila repens (Benth.) Benth. (synonym Limnophila conferta Benth.), an aquatic herb also occurring in South-East Asia, contains 'ALFA'-phellandrene (52.2%) and thymol (38.2%). The antifungal activity of a 1:50 dilution in ethylene glycol was found to be of the same order of magnitude as that of griseofulvin (100 µg/0.1 ml) for Aspergillus niger, Candida albicans and Rhizopus nigricans (synonym R. stolonifer). Against dermatophytes (Trichophyton mentagrophytes and Microsporum gypseum), the oil at a concentration of 100 µg/ml inhibited growth whereas miconazole was effective at a concentration of 10 µg/ml. The oil also possessed good anthelmintic activity against Taenia sp. and Ascaris galli. The crude alcoholic extract showed significant reduction in the epithelization period compared with that of controls in excision wound models. Nevadensin isolated from the plant showed good anti-inflammatory activity in an acute inflammation model and exhibited moderate cytotoxic activity and anti-tubercular activity.

Annual or perennial, aquatic or semi-aquatic herbs, often aromatic when bruised, glabrous or hairy; stems erect or prostrate and rooting at the nodes, simple or branched. Submerged leaves verticillate, pinnatifid, glabrous; aerial leaves opposite to verticillate, entire to serrate, laciniate or pinnately divided, punctate; petiolate or not. Inflorescence a lax or compact, terminal or axillary spike or raceme, or flowers solitary and axillary; bracteoles 0 or 2. Flowers bisexual, slightly zygomorphic, 5-merous; calyx tubular, deeply 5-lobed, lobes subequal, tube with 0B-5 or 10 prominent veins; corolla tubular or infundibuliform, 5-lobed, bilabiate, adaxial lip outside in bud, entire or 2-lobed, abaxial lip 3-lobed, erect or spreading; stamens 4, included, didynamous, filaments filiform, anthers free, loculi stipitate; ovary superior, glabrous, style filiform, deflexed at apex, stigma bilamellate. Fruit an ellipsoid to globose capsule, septically 4-valved, valves bifid, with numerous seeds. Seed prismatic, small, 0.2-B0.3 mm long, both ends truncate.

Limnophila can be found flowering and fruiting throughout the year. The production of fruits by cleistogamy on submerged stems was found in several Limnophila species, including Limnophila sessiliflora, but has not been observed in Limnophila indica. Hybridization is recorded from tetraploid Limnophila indica and Limnophila sessiliflora, both common aquarium plants.
Several varieties have been distinguished in Limnophila indica by earlier authors, but it was found that factors such as light intensity, daylength, water depth and water flow produced these varieties. In Sri Lanka, the flowers of Limnophila indica open between 10—15 h.

Limnophila belongs to the tribe Gratioleae and subtribe Stemodiinae, and is closely related to Stemodia and Morgania. Limnophila is divided into 4 sections: sect. Limnophila (e.g. Limnophila indica) has finely divided submerged leaves, and aerial leaves with parallel veins, section Connatae has similar aerial leaves, but lacks submerged leaves, section Integrifolieae (e.g. Limnophila rugosa) has pinnately veined leaves and a calyx without striations, while section Striatae (e.g. Limnophila aromatica, Limnophila erecta) has similar leaves as the latter but a striate calyx. Most Limnophila species show a large variation in form of the leaves, hairiness and habit.

All Limnophila are aquatic or semi-aquatic herbs occurring in marshes, along riversides or forest paths, mostly at low altitudes. Limnophila is also a weed of rice fields.

Limnophila normally propagates by seeds or rooted stems. Also, root tips (1 cm long) from in vitro grown plants of Limnophila indica have been cultured in liquid medium with 2% sucrose. The explants floated horizontally on the surface, became green, and their tips started to grow geotropically into the medium. In 4 weeks, 4—6 shoot buds each were differentiated in 84.5% of the cultures. No buds formed at the cut end or near the growing root tip. Histological studies of the roots showed that the buds originated from proliferating cortical cells, which had prominent chloroplasts and starch grains. The shoot buds grew successfully into entire plants.

Limnophila aromatica is not easily cultivated as it needs a permanent water supply, and the tender, fleshy stems can be easily damaged.

Plants of Limnophila aromatica are harvested from the wild in Vietnam, when they are at least a year old. Young plants are used as a condiment.

In Vietnam, the plants of Limnophila aromatica are dried before use.

All Limnophila species mentioned here have a large area of distribution, either naturally or as a result of cultivation, and do not seem to be at risk of genetic erosion. There are no known breeding programmes.

Essential oils and flavonoids of Limnophila show interesting pharmacological activities. More research is, however, needed to fully evaluate this potential. The plants might be of interest as a local source of e.g. antifungal or anthelmintic preparations.

de Guzman, C.C. & Siemonsma, J.S. (Editors), 1999. Limnophila rugosa (Roth) Merrill. Plant Resources of South-East Asia No 13. Spices. Backhuys Publishers, Leiden, the Netherlands. p. 257.
Liu, M.C., Chen, Z.S., Chung, L.C., Yang, M.S., Ho, S.T. & Chen, M.T., 1991. Studies on hypotensive constituents of Limnophila rugosa. Chinese Pharmaceutical Journal 43(1): 35-B40.
Perry, L.M., 1980. Medicinal plants of East and Southeast Asia. Attributed properties and uses. MIT Press, Cambridge, Massachusetts, United States & London, United Kingdom. p. 383.
Philcox, D., 1970. A taxonomic revision of the genus Limnophila R.Br. (Scrophulariaceae). Kew Bulletin 24: 101B-170.
Rao, J.V., Aithal, K.S. & Srinivasan, K.K., 1989. Antimicrobial activity of the essential oil of Limnophila gratissima. Fitoterapia 60(4): 376-B377.
Rao, S. & Ram, H.Y.M., 1981. Regeneration of whole plants from cultured root tips of Limnophila indica. Canadian Journal of Botany 59(6): 969-B973.

G.H. Schmelzer

Limnophila aromatica
Limnophila erecta
Limnophila indica
Limnophila rugosa

Schmelzer, G.H., 2001. Limnophila R.Br.. 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:
Limnophila aromatica
Limnophila erecta
Limnophila indica
Limnophila rugosa