Polygalasaponin aglycone

Polygala tenuifolia (Polygala sibirica), or slender lobe milkwort, yuan chih, yao jao, hsiao ts'ao (Chinese), is a very slender perennial herb that grows to a height of 20 cm on sun-exposed hillsides, roadsides, and stony slopes of Korea, China, and Mongolia. The leaves are linear and the flowers are whitish (Fig. 41).

In China, the plant is known to promote mental powers. It is used to treat cough, jaundice, hysteria, convulsions, mammary abscess, and gonorrhea. The leaves are used for sperm leaking. The roots and leaves are used to promote urination. In Cambodia, Laos, and Vietnam the roots are used to calm and to treat cough. In Korea, the plant is used to treat psychotic illnesses. In vitro binding studies suggested a potential mechanism for its antipsychotic action, as saponins known as polygalasaponins bind to both dopamine and serotonin receptors. Polygalasaponins (25-500 mg/kg) showed receptor antagonist properties, and their possible utility as antipsychotic agents has been subjected (22). It would be interesting to know whether further study on the precise molecular activity of polygalasaponin discloses any original molecular pathways in the

Fig. 41. Polygala tenuifolia.

search for serotonin re-uptake inhibitors. Because saponins are very polar, how could it cross the hemato-encephalic barrier and reach the brain unless injected intracranially? Is the genin instead neuroactive?

Note that the plant elaborates a series of carboline alkaloids including 1-carbobutoxy-p-carboline, N9-formylharman, 1-carboethoxy-p-carboline, 1-carbomethoxy- p-carboline, perlolyrine, harman, and norharman (23). An interesting development would be to assess these alkaloids for central nervous activity.

Polygala japonica Houtt. (Polygala sibirica non L.), or dwarf milkwort, himehagi (Japanese), is a little perennial herb of Australasia. The leaves are tiny and broadly elliptic, and the flowers are purplish-blue (Fig. 42).

It is medicinally used from Korea to Cambodia, Laos, and Vietnam. In Korea, the plant is used as an aphrodisiac for males and the elderly. In Japan, a decoction of the root is drunk to treat cough, invigorate, and treat tuberculosis. In Taiwan, the plant is an external remedy for snake bites. In Cambodia, Laos, and Vietnam, the roots are used to treat bronchitis, amnesia, and to stimulate memory and urination. The antitussive property is very probably owed to polygalasaponins, which are known to abound in the plant (24-26). It would be interesting to know whether the tonic properties mentioned here are owed to serotoninergic mechanisms. What is the alkaloidal content of this herb?

Fig. 42. Polygala japónica.
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