Strobilanthes (PROSEA)
Introduction |
Strobilanthes Blume
- Protologue: Bijdr. fl. Ned. Ind.: 781, 796 (1826).
- Family: Acanthaceae
- Chromosome number: x= 8;S. cusia:n= 8, 2n= 32
Origin and geographic distribution
Strobilanthes is one of the largest genera in Acanthaceae , with approximately 200 species, and is distributed in tropical and subtropical Asia. Some species are cultivated within this region or elsewhere.
Uses
The leaves and sometimes the roots of S. cusia are important in traditional medicine in Indo-China and China. They are used internally to treat irregular menstruation, bleeding after abortion, fever, vomiting, tonsillitis and haemoptysis, and in cases of eruptive epidemic diseases such as influenza, meningitis and erysipelas, and externally against eczema, impetigo, haemorrhagic gingivitis, and snake and insect bites.
In traditional medicine in Indonesia S. crispa leaves are used to treat kidney stones and diabetes.
The tubers of S. acrocephala T. Anderson are used in Vietnam as a blood tonic, sexual stimulant, sedative, to treat cough and to promote lactation of women after childbirth. In India, pounded leaves of S. auriculata Nees are rubbed on the body to treat intermittent fever.
Properties
Leaves of S. crispa contain high amounts of minerals including potassium (51%), calcium (24%), sodium (13%), iron (1%) and phosphorus (1%), and of water-soluble vitamins (B1, B2 and C). They also contain catechins, alkaloids, caffeine and tannin. They showed high antioxidant activity, and it has been suggested that a daily dose of a herbal tea prepared from the leaves could contribute to the additional nutrients and antioxidants needed in the body to enhance the defence system, especially toward the incidence of degenerative diseases. An extract of S. crispa leaves showed potent inhibitory activity on avian myeloblastosis virus reverse transcriptase, and no cytotoxicity. A leaf infusion of S. crispa showed dissolving capacity on calcium stones. Verbascoside (an iridoid-glucoside), caffeic acid derivatives and flavonoids have been isolated from S. crispa .
The quinazolinone alkaloids 4(3H)-quinazolinone and 2,4(1H,3H)-quinazolinedione were isolated from S. cusia in China. The first compound showed antitumour, antiviral and immunomodulating activities, and the second compound hypotensive action. The indoloquinazolinone alkaloid tryptanthrin, also isolated from S. cusia , showed potent activity against resistant strains of mycobacteria, whereas a 1% tryptanthrin solution in alcohol showed good activity against some skin fungi, without being toxic. Indoles, which are the main compounds in S. cusia , have noticeable action on the womb; they showed contractive effect on isolated uterus of guinea-pigs. The indole derivatives indigo and indirubin (indigo-red, the red-coloured natural isomer of indigo) have been isolated from whole S. cusia plants. The latter compound showed anticancer activity, and is an official drug in China for the treatment of chronic granulocytic leukaemia. Clinical tests showed that the therapeutic efficacy of indirubin was comparable to that of busulfan, yet without bone marrow suppression, and with few side effects, which are mainly gastro-intestinal. Indirubin is now produced synthetically.
Other compounds isolated from S. cusia include the triterpenes lupeol, betulin and lupenone.
S. cusia extracts induce abortion in animals in the early stages of gestation.
Botany
Erect or decumbent herbs or much-branching shrubs. Leaves opposite, often those of a pair unequal, simple, entire to dentate or crenate, with cystoliths; petioles connected by a transverse ridge; stipules absent. Inflorescence a spike or head, terminal or in the axil of a bract, aggregated in erect or nodding racemes or panicles, or composed of solitary flowers. Flowers bisexual, rather large, 5-merous, subsessile; calyx deeply cleft or parted, with linear, equal or unequal segments; corolla with funnel-form tube, curved or straight, narrow below, much broader above, hairy in 2 rows inside, lobes unequal, spreading; stamens 4, didynamous, exserted or included, sometimes 2 rudimentary, filaments more or less connected at base; ovary superior, 2-celled, style slender, recurved, with 2 unequal stigmatic lobes. Fruit an oblong or linear capsule, 2-4-seeded. Seeds papillate or short-hairy.
Several Strobilanthes species are monocarpic, i.e. they take some time, often about 12 years, to flower and then die after fruit setting. This may result in mass flowering and dying off, comparable to bamboos.
Strobilanthes has an enormous range of variation and has been subdivided into numerous smaller genera, which are, however, often ill-defined. It is one of the poorly understood Acanthaceae genera.
Ecology
S. crispa occurs in anthropogenic habitats in the lowland of Java, whereas S. cusia is only occasionally planted in the Malesian region. The latter is hydrophilic and often grows in the shade.
Management S. cusia can be propagated by root cuttings, and plants are pruned 2-3 times a year when cultivated for dye production. Harvesting of leaves can start 6 months after planting.
Cell suspension cultures of S. dyeriana Masters (apparently only known from cultivation) initiated from leaf tissue have been maintained on agar and solid B5 Gamborg media. One of the callus lines produced the anthocyanins cyanidin-3,5-diglucoside and peonidin-3,5-diglucoside in the presence of indole-3-acetic acid. These anthocyanins are also present in intact plants. The cultures produce the glucoside of p-methoxyphenethylamine when this latter compound is used as the substrate.
Genetic resources
S. cusia has been much collected for medicinal purposes and as a dye plant, and has become rare in the wild. Conservation measures are desirable for wild populations. S. crispa seems less vulnerable. It is striking that in regions where Strobilanthes is comparatively well studied the occurrence of endemic species is high, e.g. in Sri Lanka where over 80% of the species are endemic. This indicates that Strobilanthes is in general liable to genetic erosion.
Prospects
Some of the compounds isolated from S. cusia , such as indirubin, and their pharmacological activities have greatly stimulated interest in antitumour agents from natural resources, and show that plants are still a considerable source of compounds active against important diseases. Recent findings also show that S. crispa may have prospects as a modern medicinal plant with stimulatory activity on the defence system of the body against diseases. However, still more research is needed to develop the potential applications of Strobilanthes in medicine.
Literature
338, 731, 876.
Selection of species
Authors
Nguyen Kim Bich & Nguyen Tap