ISTOD UZKOLISTNY, OR TONKOLISTNY — POLYGALA TENUIFOLIA WILLD.
Both species are low-growing perennials with short taproots (15–20 cm in length) and numerous low, slender stems. The stems of Polygala tenuifolia are glabrous, while those of Polygala sibirica are shortly appressed-pubescent. The leaves are sessile; in Polygala tenuifolia, they are linear, while in Polygala sibirica, they are broader and lanceolate. The flowers are blue and irregular.
They grow in steppes, on sandy meadows, in sparse pine forests on mountains, favoring southern rocky slopes. Polygala tenuifolia is found in the Altai region, in Eastern Siberia around Lake Baikal, and is particularly common in Transbaikalia. Polygala sibirica has a wider range, growing in Siberia and extending westward into the European part of Russia; it is also found in Ukraine, the Volga region, and the Caucasus.
The roots of Polygala — Radix Polygalae — are dug up in the fall, shaken free of soil, which easily falls off (there is no need to wash them with water), trimmed to remove the stems, and dried outdoors in the shade or sunlight. After drying, any remaining soil is removed by shaking the roots over sieves.
The roots of both species contain saponins. Polygala sibirica is richer in saponins, which are also present in its aerial herbaceous parts, unlike the aerial parts of Polygala tenuifolia, which do not contain saponins. Two sapogenins have been isolated from the roots of Polygala tenuifolia. Additionally, the roots contain a glycoside that releases methyl salicylate, fatty oil, and no starch.
The root of Polygala is used as a decoction for bronchitis as an expectorant. It serves as a substitute for imported American senega (Polygala senega L.). A decoction of 10:200 is prescribed with the addition of ammonium-anise drops, 1 tablespoon 4 times a day.
In the Caucasus mountains, the Anatolian istod — Polygala anatolica Boiss. et Heldr. — is found.