Sida (PROSEA)
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Introduction |
Sida L.
- Protologue: Sp. pl. 2: 683 (1753); Gen. pl. ed. 5: 306 (1754).
- Family: Malvaceae
- Chromosome number: x= 7, 14; S. acuta: 2n= (18), 28; S. cordifolia: 2n= 28; S. rhombifolia: 2n= 14, (18), 28, (36)
Major species
- Sida acuta Burm.f.,
- S. cordifolia L.,
- S. rhombifolia L.
Origin and geographic distribution
Sida is a large tropical and subtropical genus comprising 150-200 species. About two thirds of these species occur only in the New World, but some are restricted to South-East Asia, Australia, the Pacific Islands or Africa. Several species, like S. acuta , S. cordifolia and S. rhombifolia, have been widely distributed throughout the tropics for over a century
Uses
In general, the decoction, infusion or pressed juice of the mucilaginous leaves and bitter roots of Sida are used for cooling, emollient, diuretic and febrifuge purposes, to treat gonorrhoea and rheumatism and externally as a poultice for boils, ulcers, swellings, cuts, coughs and chickenpox. The crushed leaves or roots are put on the head for headache, and on the gums for toothache. The leaves are used for cooling of fever in small children, the root for high fever, constipation, colic and chronic bowel complaints. In decoction, the plant may be used as an emmenagogue. In Papua New Guinea, the Philippines and Fiji, a decoction of the leaves, the juice of the leaves mixed with honey, or the root juice in water is given for diarrhoea or dysentery. In Borneo, Vietnam and Central Africa, the leaves or roots are used as an abortifacient.
In Indo-China, the roasted leaves of S. rhombifolia make a refreshing drink, while in South America, leaves and shoots are used as a vegetable. Most Sida species are appreciated as a fodder, and are widely used as fibre crops. S. acuta is cultivated in Mexico and S. rhombifolia in India, Australia, Africa and America as a fibre crop. In India, the charcoal of S. rhombifolia may be used for blackening teeth.
Production and international trade
Sida species are used and traded at a local level only, for medicinal purposes. In Peninsular Malaysia, the Chinese herbalists stock S. acuta and S. rhombifolia plants.
Properties
Many Sida species contain ephedrine, a pseudo-alkaloid, biosynthetically derived from the amino acid phenylalanine. Ephedrine acts as a sympathomimetic on the body, which means that its effects are similar to those of the sympathetic (adrenergic) neurotransmitters like noradrenalin and adrenalin (also known as norepinephrine and epinefrine). The mechanism of action of ephedrine is of the indirect type: the substance does not activate adrenergic receptors directly, but it facilitates the release of neurotransmitters from sympathetic nerves. Pharmacological effects of ephedrine include e.g. stimulation of the heart rate and cardiac output, together with a variable increase of the peripheral resistance; as a result it usually increases blood pressure. In the lungs, it promotes bronchodilatation, acceleration and intensification of respiration. It may increase the resistance to the outflow of urine in the bladder. Furthermore, ephedrine crosses the blood-brain barrier, it has a stimulating psychic effect: stimulation of the attention and concentration, decrease of the sensation of fatigue and the need to sleep, and thus qualitatively it resembles an amphetamine. Because of the numerous contraindications, drug interactions and required precautions, the compound is no longer used very often. In the United States, ephedrine-containing products are sometimes marketed as slimming aids. Over a period of 2 years, 500 reports were received of adverse events in persons who consumed dietary supplementary products containing ephedrine and related alkaloids (pseudo-ephedrine, nor-ephedrine and N-methyl ephedrine).
The alkaloids ephedrine (0.07 %) and cryptolepine were isolated from the roots of S. acuta. The latter compound is also present in the aerial parts. The seeds, like those of S. rhombifolia, contain up to 0.26% alkaloids, as well as sterculic (11%) and malvalic acid (1.7%). The water soluble portion of the alcoholic extract of S. acuta exerts spasmodic action on the smooth muscle preparations of ileum, trachea, uterus and heart of experimental animals. Thus, the activity of the extract is similar to that of acetylcholine. The untreated seeds in dung heaps show antibacterial activities on Bacillus subtilis, Escherichia coli, Pseudomonas cichorii, and Salmonella typhimurium. Furthermore, a leaf extract exhibits strong feeding deterrence and toxicity against the larvae of the insect pest Earias vittella.
The roots of S. cordifolia are very mucilaginous, and contain the chinazoline alkaloid vasicine (= peganine). The seeds contain up to 0.3% alkaloids, mainly ephedrine, and a fatty oil (3%) containing the cocacinegenic acid coronaric acid. Pharmacological effects of extracts of the plant include: antiprotozoal activity against Entamoeba histolytica strain STA by an ethanolic extract, and depression of blood pressure in cats and dogs. Furthermore, an extract of the aerial parts and the roots show analgesic, anti-inflammatory and hypoglycaemic activities. The methanolic and aqueous extracts of whole plants finally showed significant antihepatoxic activity against CCl4-, paracetamol- and rifampicin-induced hepatotoxicity.
Leaves and roots of S. rhombifolia contain ephedrine. The ethanolic extract of the plant depresses the activities of the smooth muscles of the ileum of guinea-pig preparations. The methanolic plant extract shows antimicrobial activity against Aspergillus ochraceus, Candida albicans, C. intermedia, Cunninghamella elegans, Pseudomonas aeruginosa and Staphylococcus aureus. Finally, in a screening assay, the leaf extract exhibited anticancer activity and anti-HIV activity against 60 human cell lines tested.
Adulterations and substitutes
The roots and leaves of Abutilon, Triumfetta and Urena in decoction are used as an emollient in the same way as those of Sida.
Description
- Prostrate, creeping or erect herbs or shrubs, annual to shortly perennial, often stellate pubescent.
- Leaves alternate, entire or lobed; petiole present; stipules present.
- Flowers axillary or on axillary side-shoots, sometimes combined into a leafy panicle or spike, pedicel present, epicalyx absent; calyx 5-lobed, corolla with 5 petals, joint at the base, mostly yellow; stamens numerous, joined in a tube, monadelphous, ovary 4-12-celled, carpels verticillate, 1-ovuled; styles as many as the carpels, connate at base, stigmas capitate.
- Fruit a capsule, mericarps indehiscent or apically dehiscent, aristate or not, mature ones separating from the persistent central column.
- Seedling with epigeal germination.
Growth and development
S. acuta, S. cordifolia and S. rhombifolia are considered noxious weeds in many crops and pastures, because of the tough stems and the ability to grow fast from seed. Overgrazing will cause a rapid increase of the weeds, as the stems are unpalatable to cattle. S. rhombifolia has well developed roots and grows well even under dry conditions.
Other botanical information
It has been suggested that on the basis of the morphological and geographical diversity, Sida could be of polyphyletic origin. It is morphologically fairly close to Abutilon and Wissadula, and all lack the epicalyx.
Ecology
The Malesian Sida species are mainly sun-loving herbs or undershrubs, usually occurring in open locations, especially in lowland areas. Many of them are restricted to seasonally dry parts. The treated Sida flower throughout the year when water is available, and the flowers open in the morning and wither in the afternoon.
Propagation and planting
Sida produces large amounts of seed. Seeds from S. acuta have a germination rate of 54%, a month after harvesting. The majority of the seeds of S. rhombifolia are dormant 12-24 months after maturity. The optimum temperature range for germination is 25-35 °C.
Diseases and pests
A common insect found on Sida is whitefly (Bemisia tabaci), which transmits a range of viruses, including Sida golden mosaic virus, cassava mosaic virus, okra leaf curl, tobacco leaf curl and tomato yellow leaf curl. S. acuta is a host for Aphis gossypii, which transmits cotton leaf roll disease. Mycoplasm-type organisms cause yellow symptoms on S. cordifolia and S. rhombifolia in Burkina Faso. S. cordifolia is a common host for several nematodes, including Meloidogyne incognita.
Harvesting
Generally, whole plants of Sida are harvested, including the roots.
Handling after harvest
Sida species are mostly used fresh, but can also be dried for storage.
Genetic resources and breeding
The Sida species dealt with, except S. javensis, are widely distributed, also as weeds, and locally rather common in open and disturbed areas. They are not likely to succumb to the threats of genetic erosion. Small germplasm collections of S. rhombifolia are kept in Russia and in the United Kingdom.
Prospects
Sida might be of interest as a local industrial source of the alkaloid ephedrine. However, as ephedrine can also be produced synthetically, and as its use in medicine is rapidly becoming obsolete, it is doubtful whether it will be a major source.
Literature
- Ali, A.M., El Sharkawy, S.H., Hamid, J.A., Ismail, N.H. & Lajis, N.H., 1995. Antimicrobial activity of selected Malaysian plants. Pertanika 18(1): 57-61. (in Malaysian)
- Bruneton, J., 1995. Pharmacognosy, phytochemistry, medicinal plants. Technique & Documentation Lavoisier, Paris, France. pp. 712-713.
- Kanth, V.R. & Diwan, P.V., 1999. Analgesic, antiinflammatory and hypoglycaemic activities of Sida cordifolia. Phytotherapy Research 13(1): 75-77.
- Konate, G., Barro, N., Fargette, D., Swanson, M.M. & Harrison, B.D., 1995. Occurrence of whitefly-transmitted geminiviruses in crops in Burkina Faso, and their serological detection and differentiation. Annals of Applied Biology 126(1): 121-129.
- Muanza, D.N., Euler, K.L., Williams, L. & Newman, D.J., 1995. Screening for antitumor and anti-HIV activities of nine medicinal plants from Zaire. International Journal of Pharmacognosy 33(2): 98-106.
- Van Borssum Waalkes, J., 1966. Malesian Malvaceae revised. Blumea 14(1): 1-251.
Selection of species
Authors
- Balu Perumal
