Chemistry

N. P. Maksyutina, V. I. Litvinenko

Galein—a New Flavonoid from Goat’s Rue, Galega officinalis L.

(Presented by Academician A. I. Oparin, September 2, 1963)

Goat’s rue, Galega officinalis L., is a perennial herbaceous plant of the legume family.

Goat’s rue is of interest for investigation as a valuable medicinal and fodder plant \((^{1-3})\). Chemical investigation of the seeds of goat’s rue showed the presence in them of sterins, the alkaloid galegine, guanidine bases, and the flavonoids galuteolin and luteolin \((^{1,4-6})\). Alkaloids and saponins have been found in the herb of this plant \((^1)\).

The subject of our investigations was the flowers of goat’s rue. From the flowers a flavonoid was isolated, which we have named galein. On acid hydrolysis of galein, the aglycone—galetin—was obtained. As is evident from the data in

Table 1

Properties of the flavonoids galein and galetin

Tables 1 and 2, galein is a glycoside containing two molecules of rhamnose. The aglycone galetin, in all probability, is a new flavonoid with five hydroxyl groups. The location of the hydroxyls in the 3, 5, 7, and 4′ positions was established by spectral investigations and confirmed by qualitative reactions, while the hydroxyl in position 6 was detected by the color qualitative Bargellini reaction \((^7)\). These data allowed us to propose the following formula for galetin:

Galetin (3,5,6,7,4′-pentaoxyflavone) has evidently been isolated by us from nature for the first time.

Table 2

Spectral characteristics of the flavonoids galein and galetin

ones, although its partially methylated and glycosylated derivatives—pendulin\(^8\) and fogeletin\(^9\)—were known previously.

Comparison of the physicochemical properties of the glycoside galein and of the aglycone galetin permits the conclusion that galein is 3,6-dirhamnoside of galetin.

Isolation of galein. 2 kg of dried flowers of Galega officinalis are extracted with 96% ethanol. The alcoholic solution is evaporated in vacuo, the residue is treated with water, and the solution is filtered. On standing, plate-like yellow crystals separate from the aqueous filtrate, m.p. 182–184°. The substance gives positive reactions for flavonoids: the cyanidin reaction, and reactions with alkali solution, lead acetate, aluminum chloride, ferric chloride, and zirconyl chloride. Yield 1.2%.

Galetin. 1.0 g of galein is dissolved in 30 ml of 3% hydrochloric acid in 50% ethanol and hydrolyzed by heating for 30 min on a boiling water bath. Yellow needles precipitate, m.p. 305–307°. The aglycone gives positive reactions: the cyanidin reaction, the Bargellini reaction, and reactions with ferric chloride solution, lead acetate, and zirconyl chloride with citric acid.

After separation of the aglycone, the acidic hydrolysate is neutralized to pH 7 and evaporated in vacuo to dryness. The residue is treated with absolute alcohol, filtered, and chromatographed in the systems: n-butanol—acetic acid—water (4 : 1 : 5) and n-butanol—pyridine—water (6 : 4 : 3), alongside standards of known monosaccharides. Only rhamnose was found in the hydrolysate.

Research Institute of Chemical and Pharmaceutical Sciences
Received 2 IX 1963

CITED LITERATURE

1. S. E. Zemlinskii, Medicinal Plants of the USSR, Moscow, 1958, p. 427.
2. F. V. Selecky, Farmacia, 24, 198 (1955).
3. Forage Plants of Hayfields and Pastures of the USSR, 2, Moscow, 1951.
4. G. Barger, F. D. White, Biochem. J., 17, 836 (1923).
5. G. Tanret, C. R., 158, 1182 (1914).
6. E. Späth, S. Prokopp, Ber., 57, 474 (1924).
7. K. Venkataraman, Fortsch. Chem. Org. Naturstoffe, 17, 9 (1959).
8. S. E. Flores, J. Herran, Tetrahedron, 2, 308 (1958).
9. S. Rangaswami, K. H. Rao, Proc. Indian Acad. Sci., 49, 241 (1959).