A low-growing perennial plant with a creeping rhizome, from which arise simple or branched aerial stems. The leaves are compound, trifoliate, grayish-green, with short petioles. Leaflets are elongated, narrow, and pointed at the apex, grayish-green, glabrous on top, and with pressed hairs on the underside; stipules are lanceolate and much longer than the petiole, giving the leaf a 5-fold appearance. The flowers are large, arranged in short terminal racemes, yellow in color. The flag of the corolla is almost round, deeply and narrowly notched at the apex (a characteristic feature). There are 10 free stamens (a characteristic feature shared with sophora and some other related genera). The fruit is a dark brown, oblong, flat pod (not bead-like, distinguishing it from sophora). The seeds are black, spherical-ovoid, with a light, rounded hilum. The plant flowers in June and the fruit ripens in September. The entire plant is toxic.
It grows in lowland saline or sandy areas, gentle slopes, and is found as a weed in crop fields. It is predominantly distributed in the steppe and forest-steppe zones of Eastern and Western Siberia, and less frequently in Kazakhstan; in the European part, it is found in the southwestern Urals.
The aerial part of Thermopsis is harvested during the flowering period. Seeds are collected separately from ripened pods, which are harvested from September to November, threshed, winnowed, and sieved to remove broken pod fragments.
The herb contains alkaloids ranging from 0.5 to 2.5%; according to pharmacopoeia, the content should be at least 1% (if it exceeds 1%, a corresponding recalculation is made).
Five alkaloids have been isolated from the herb. The main one is thermopsin, with accompanying alkaloids including homothermopsin, anagyrine, pachycarpine, and methyl-cytisine; two additional alkaloids have been discovered later. Thermopsin contains two quinolizidine rings and is an isomer of anagyrine, closely related to pachycarpine.
Additionally, a flavonoid glycoside, thermopsilanthin, is isolated from the herb in the form of greenish-yellow crystals, which accumulate in the epidermal cells. It is insoluble in water, alcohol, and other organic solvents, but easily dissolves in alkaline solutions, even when cold.
The seeds contain 2–3% alkaloids, mainly cytisine, which is extracted in pure form at alkaloid factories. It also belongs to the lupinane group.
Herbal preparations are used as a remedy for coughs. A water infusion of the herb (0.6 g per 200 ml) is prescribed, with a tablespoon taken three times a day, or tablets of dry extract (0.05 g) are taken, 1 tablet three times a day.
Cytisine is available in ampoules under the name «Cytiton.» It is injected intravenously in doses of 0.5–1 ml to stimulate the respiratory center; «Tabex» tablets, containing 0.0015 g of cytisine, are used to aid in smoking cessation. One tablet is taken five times a day, then the dosage is reduced to 1–2 tablets.
Thermopsis alternifiora Rgl. et Schmal
This species grows in Central Asia and the lower mountain belts. The herb contains up to 3 alkaloids (including 1% cytisine), and the seeds contain about 3% of the total alkaloid content (up to 0.8% cytisine). Other alkaloids such as pachycarpine are also present, but thermopsin is absent. The herb and seeds can serve as a source of cytisine.
Piptantus namus L. contains the alkaloid piptantin, which is also a quinolizidine derivative.