Periploca Graeca

PERIPLOCA GRAECA L., periploca, silk vine, a perennial liana of the family Asclepiadaceae, distributed along the shores of the Black and Mediterranean Seas, in the Caucasus, and in Asia Minor. The cylindrical rhizome gives rise to several thin, long stems reaching 2.5 cm in diameter and 8 m in length. The leaves are oval with smooth and entire margins. The flowers are small, five-petaled, brownish-purple on the inside and yellowish-green on the outside. Long purple nectaries curve spirally over the stamens (5 pieces), to which two-celled anthers are attached. The developed fruit is a double follicle containing numerous flat, dark brown, almost black seeds; the seeds are provided with a long white silky tuft. As a medicinal plant, it was first studied by Russian scientists Lehmann and Burzhinsky. The active principles are contained predominantly in the bark of the plant, from which Lehmann isolated the glycoside periplocin (with the empirical formula C₃₁H₄₈O₁₂), which turned out to be extremely close in its chemical properties to the glycosides of the digitalis group. Periplocin dissolves easily in ethyl and amyl alcohol, and in water (1:125; in cold water easier than in boiling water). Burzhinsky investigated periplocin pharmacologically and confirmed its action on the heart, which is characteristic of the digitalis group of glycosides. Both periplocin and conventional extracts of Periploca graeca were clinically examined by Levashev, and the beneficial effect of these preparations in cases of heart disease where digitalis treatment is indicated was confirmed. Re-investigating the active principles of Periploca graeca, Jacobs and Hoffmann isolated from the plant's bark the glycoside periplocymarin, named by them thus for its similarity to the glycoside cymarin. Examination of the plant's activity according to FUP (expression of the amount of active principles in frog units of action - F. U.) shows that 1 g of dried bark contains up to 100 F. U. Shoots and leaves contain from very insignificant amounts up to 30 F. U. in 1 g. It is not possible to isolate the active principles from seeds using conventional methods. The comparatively high activity of Periploca graeca bark in experiment does not yet allow a direct transfer of these data to the clinic, since many heart-acting glycosides, possessing high activity in experiments on frogs, are little active in the clinic (for example, lily of the valley glycosides). Analysis of the action of bark extracts (alcoholic and aqueous) on isolated frog hearts and on cats with slow intravenous administration of weak solutions (Hatcher and Brody method) confirms that the nature of the action of silk vine glycosides is similar to the nature of the action of digitalis glycosides. Data from experimental pharmacological research lead to the conclusion that there is a comparatively rapid onset of action and apparently an absence of cumulative properties of the active principles of Periploca graeca. Purified and standardized preparations of the so-called new galenical type can be prepared from the plant's bark for internal use and injections. The use of Periploca graeca growing in the Caucasus may have industrial significance.