Kaempferol and quercetin from Nigella arvensis

Abstract

B. M. K i r i c h e n k o , K. E . K o r e s h e h u k , G. A. D r o z d , a n d A . A. K r e m z e r a r v e n s i s UDC 547.972We have studied the epigeal part of Nigella arvensis L., family Ranunculaceae Juss.The plant was extracted with 70% ethanol. The extract was deposited on a column of polyamide s o rbent and eluted first with water until flavonoids appeared in the eluate, and then with 70% ethanol. The combined flavonoids were heated in 10% hydrochloric acid on the water bath for 6 h. In the hydrolytic p r o c e s s the absence of C-glycosides was established [1]. The hydrolysate was diluted with water and passed through a column of polyamide sorbent. After the column had been washed with water to neutrality, the aglycones were desorbed with 96% ethanol, and the solution was evaporated and rechromatographed, being eluted with m i x t u r e s of chloroform and ethanol. Three substances were isolated.The first substance had mp 273-275°C, Rf 0.46 (60% acetic acid) and 0.56 [benzene-ethyl a c i d -f o rm a m i d e (70 : 30 : 2 : 1)], )tma x in ethanol 265, 296, and 370 nm. UV spectroscopy showed the p r e s e n c e of free 3-, 5-, 7-, and 4*-hydroxy groups [2]. Phloroglucinol and p-hydroxybenzoic acid were found in the products of alkaline degradation.The results obtained, and also a chromatographic comparison with an authentic sample,enabled this substance to be identified as 3, 4", 5,7-tetrahydroxyflavone or kaempferol.The second substance had mp 311-313°C, Rf 0.35 (60% acetic acid) and 0.14 [benzene-ethyl a c e t a t eacetic a c i d -f o r m a m i d e (70 : 30 : 2 : 1)], hmax in ethanol 270, 310, and 375 nm. UV spectroscopy showed the p r e s e n c e of free hydroxy groups in positions 3, 5, 7, 3", and 4". Phloroglucinol and protocatechuic acid were found in the products of alkaline degradation.By its physicochemical p r o p e r t i e s , UV spectroscopy, and a comparison with an authentic sample, the substance was identified as 3, 3", 4", 5, 7-pentahydroxyflavone or quercetin.The third substance, having Rf 0.55 (60% acetic acid) and 0.93 [ b e n z e n e -e t h y l a c e t a t e -a c e t i c a c i df o r m a m i d e (70 : 30 : 2 : 1)] could not be obtained in the crystalline state.