Quercetin araboglycosides from some species of rhododendron

QUERCETIN OF ARABOGLYCOSIDES FROM SOME SPECIES RHODODENDRON ]~. T . O g a n e s y a n , V. A . B a n d y u k o v a , and A. L. Shinkarenko UDC 547.972 We have previously r e p o r t e d the flavonoid composition of the Pontic azalea, the Caucasian rhododendron, the Dahurian rhododendron, the royal azalea, and the Kamchatka rhododendron [1-4]. Quereetin 3L - a r a b i n o s i d e was isolated f r o m all the species mentioned. As f u r t h e r chemical and physicochemical investigations have shown, the quercetin 3-arabinoside isolated from the Pontic azalea differed in its physicochemical p r o p e r t i e s f r o m the others. The queroetin 3-arabinosides f r o m the Caucasian, Dahurian, and Kamchatka rhododendrons and the royal azalea a r e identical in t h e i r physicochemical properties: mp 209-211°C (from ethanol), [ ~ ] ~ - 162°; the melting points of t h e i r methyl and acetyl derivatives a r e also identical and give no d e p r e s s i o n in a mixed sample. UV and IR s p e c t r o s c o p y also show the identity of these substances. A c o m p a r i s o n of the specific and m o l e c u l a r rotations with those given in the l i t e r a t u r e p e r m i t s the assumption that in these glycosides the L - a r a b i n o s e c o r r e s p o n d s to o~-L-arabofuranose. This is confirmed by the methyl and aeetyl derivatives f o r m e d and by differential IR spectroscopy. T h e s e facts show that in the species mentioned the quercetin is p r e s e n t in the f o r m of the 3-O-oz-L-arabofuranoside (avicularin) [5]. The quereetin 3-arabinoside f r o m the Pontie azalea has mp 240-241°C (from ethanol), [~]~ - 59°, and the melting points of the acetyl and methyl derivatives also differ from those of the arabinosides of the other species of rhododendron. On comparing the specific and m o l e c u l a r rotations with those given in the l i t e r a t u r e , it can be seen that the L - a r a b i n o s e is present in the pyranose f o r m and is r e p r e s e n t e d by o~-L-arabopyranose, which is c o n f i r m e d by the constants of the acetyl and methyl derivatives and also by differential IR spectroscopy. Thus , the glycoside isolated f r o m the Pontic azalea differs by the size of the oxide ring of the a r a b i nose and is identical with q u e r e e t i n 3 - O - ~ - L - a r a b o p y r a n o s e (guaijaverin) [5]. LITERATURE 1. 2. 3. 4. 5. ]~. ]~. E. ]~. H. T. T. T. T. E. CITED Oganesyan, V. A. Bandyukova, and A. L. Shinkarenko, Rast. Res., 4, No. 2, 240 (1968). Oganesyan, V. A. Bandyukova, and A. L. Shinkarenko, Khim. Prirodn. Soedin., 3, 279 (1967). Oganesyan and A. L. Shinkarenko, Khim. Prirodn. Soedin., 5, 179 (1969). Oganesyan, Rast. Res., 6, No. 2, 232 (1970). Khadem and Y. S. Mohammed, J. Chem. Soc., 1958, 3320. Pyatigorsk Pharmaceutical Institute. T r a n s l a t e d f r o m Khimiya Prirodnykh Soedinenii, No. 3, p. 370, May-June, 1971. Original article submitted November 27, 1970. © i973 Consultants Bureau, a division of Plenum Publishing Corporation, 227 West 17th Street, New York, N. Y. 10011. All rights reserved. This article cannot be reproduced for any purpose whatsoever without permission of the publisher. A copy of this article is available from the publisher for $15.00. 346  (...truncated)