The genus Trigonostemon has 50-60 species. This one grows throughout Southeast Asia : Myanmar, Vietnam, Laos, Cambodia and Thailand. It is found in the open rainforests of the lowlands of the Indo-Malaysian peninsula at elevations from sea level up to 1,100 m. The genus is named for a dominant three-fold symmetry: leaves are simple and triangular; the ovary holds three ovules, the triangular seeds are 5-6 mm (0.2 in) long, the fruit is a three-lobed capsule about 1 cm (0.4 in) in diameter, white flowers have 3-5 stamens.
They are shrubs up to 1.5 m (5 ft) high with slender limbs. In Thailand, where they are named Lot Thanong, ethnopharmacology uses the roots, twigs and leaves. The traditional medicine thus treats many conditions : abcesses, bruises and sprains, asthma, drug addiction, food poisoning by mushrooms and shells, constipation and snake bites, in particular by cobra snakes.
The venom of Thai cobra (Naja kaouthia) has paralytic neurotoxin activity from binding onto nicotinic acetylcholine receptors. The toxin is a polypeptide with 71 amino acids residues and five S-S disulfide bridges. It blocks nerve transmission by binding to the acetylcholine receptor on the postsynaptic membranes of skeletal muscle and/or neurons causing paralysis by preventing acetylcholine binding to the nicotinic acetylcholine receptor.
Which molecules from the plant interfere with that venom? So-called rediocides A and G: they bind to the toxin and thus inhibit its attachment to the acetylcholine receptor.
The discovery of the therapeutic uses of rediocides was multi-sided. Initially, at the end of the previous century a team in the laboratories of the Merck pharmaceutical company in Rahway, New Jersey, became interested in the flea-killing activity of the plant. They isolated an active compound and named it rediocide A. They also found that it sported a novel structure with an unusual 12-carbon macrolactone extension. This exotic structural feature led groups in China, Japan and Thaïland during the last two decades to further investigate the plant, finding in the process another half-a-dozen active rediocide molecules.