Family: Acanthaceae

Other known names: Purple Allamanda, Laurel-leaved Thunbergia, Laurel Clock Vine, Blue Trumpet Vine, Babbler’s Bill

Thai names: Rang juet, Raang Chuet, Kamlang chang phuaek, Rang yen, Aet ae, Knop cha

Botanical description:
Thunbergia laurifolia is a fast growing vigourous perennial evergreen climbingvine.
It is extremely invasive and can cover huge areas of jungle smothering the other vegetation. The leaves are 3 to 5 cm long, are oval, broad based and narrow to a pointed tip. The blue-violet, lilac to white orchid-like flowers in hanging groups are trumpets which expand to five rounded petals, one larger than the others. The seeds are in cone shaped pods 3-5 cm long. The 1 cm long seed is ejected several metres when the ripe pod bursts. The plant develops a very tuberous root system, some tubers weighing up to 70 kg which grows on a host plant. It prefers a shaded uncultivated forest environment. The flowers and the leaves are used for medicinal purposes.

Uses in Ethnic Medicine:
Thunbergia laurifolila is known in traditional Thai medicine for its detoxicant actions. The plant is frequently used in cases of alcohol abuse (hangover). In hot moist tropical climates where foods decompose rapidly due to the fast propagation of bacteria which produce dangerous toxins, and where the use of refrigerators was little known until recent times, thunbergia was a widely used folk medicine.

As Bhuddism, the state religion of Thailand does not impose any constraints concerning the consumption of alcoholic beverages, there are moments in the year where the polulation shows a tendency to over indulge and particularly on the occasion of religious and public holidays. No other country in the world has so many festive celebrations and as a result many working days are lost due to the effects of heavy partying. The government has attempted, with very little success to limit the number of these festivities. Even the new year is celebrated no less than three times; on the eve of international change of year (31 December), the Chinese New Year (the Chinese community represents a very large contingent of the population) in early February which is celebrated for up to four weeks and Songkran & Trut, the traditional Thai New Year in April which continues over a period of 5-7 days. Nowhere else in the world is the rather outmoded English expression ‘auspicious occasion’ more heavily used than in the Thai version of English as a Second Language. The use in Thailand of thunbergia is still today mainly for food and alcohol poisoning and as an antitoxin for insecticides and pesticides.

Traditional Thai Prescriptions:
Fresh leaves are boiled in water and allowed to cool. The brew is then drunk at regular intervals during the day. Also the leaves and flowers can be dried (traditionally) in the sun and taken as powder.

Pharmacognostic action and trials:

Antibacterial action:
Thunbergia laurifolia acts on streptococcus mutan, streptococcus sanguis, streptococcus sobrinius, lactobaccili, pseudomonas aeruginosa, escheria coli, staphyolococcus aureus, S. epidermis, bacillus subtilis.

Antimycotic and fungicidal action:
Candida albicans,
Powerful effect on aspergillus actinomycetemcomitans ATCC 43717 and aspergillus actinomycetemcomitans ATCC43718.

Antitoxic action:
Close observation in the areas where thunbergia laurifolia grows will reveal that in inhabited areas where insecticides are used (mosquito sprays etc.), there are hardly any thunbergia plants which have not been infested with pests while in the relatively untouched forest areas the thunbergia plants are free from infection.

The reason for this is given in an interesting research carried out by the Faculty of Veterinary Medicine, Khon Kaen University:
Effects of Thunbergia laurifolia Linn. on the parathion poisoning of rats (Parathion = E 605®) Diethyl-p-nitrophenyl-thiophosphate, insecticide from thealkylphosphate group, Acetylcholinesteerase inhibitor, highly toxic. LD (lethal dose) on humans: 5 mg per kg. body weight.

The use is forbidden in Europe.
The tests showed a significant rise in plasma cholinesterase level following feeding with thunbergia leaves or injection extract from thunbergia leaves. Twice daily one group of animals was administered 2 mg per kg body weight of parathion, and then 1 gramm per kg of thunbergia leaves. Over a period of three days a second group was injected with 2 mg per kg body weight of E605 followed after 5 minutes with an injection of thunbergia extract and again in 8 hours. The results were that treated animals in both groups were detoxicated.

It would appear that insects that come into contact with insecticides (harmless for humans) in rural areas, have detoxified themselves with thunbergia which would explain why the thunbergia plants in the urban areas have been subject to attack by insects.

Not only does thunbergia act highly effectively on liver toxins, but it also stimulates the metabolism in the liver and acts as an antiallergenic, as for example in asthma.

In contrast to Milk Thistle (silbyum marianum) which contains the active ingredient silymarin that exercises an antagonistic effect on liver toxic substances such as carbon tetrachloride and the lethal amatoxin found in the Death Cap mushroom (amanita phalloides) both of which are non water soluble, Thunbergia - which is water soluble - protects from hepatosis and stimulates the circulation.

In therapeutic situations it also inhibits liver fat deposits and liver cell toxins, such as phosphor, carbon tetrachloride, chloroform (trichloromethane), arsenic, and prolonged concentrations of alcohol and cytostatics which in extreme cases can lead to liver cell necrosis (death) and liver dystrophy (wasting away). Thunbergia can also be used as an adjuvant to chemotherapy.