Phenolic derivatives such as quinones, acid-phenols and flavonoids were successfully isolated from a n-butanolic fraction of Senecio giganteus Desf. (Asteraceae) flowers, namely jacaranone (1), 3a-hydroxy-3,3a,7,7a-tetrahydrobenzofuran-2,6-dione (2), chlorogenic acid (3), hyperoside (4), quercetin 3-O-β-D-robinobioside (5), isorhamnetin-3-O-β-D-glucuronide (6), quercetin-3-O-β-D-glucuronide (7), and isorhamnetin-3-O-β-D-glucuronide-6''-methyl ester (8). These compounds were purified through either classical polyamide filtration followed by fractionation on Si gel, or through fast centrifugal partition chromatography (FCPC). Using FCPC, the major compounds could be readily isolated from the crude n-butanolic fraction. Compounds 1-8 were identified by means of spectroscopic and spectrometric analysis (UV, 1 H, 13 C and 2D NMR, and MS). This work described for the first time the phytochemical composition of this endemic Algerian plant.
The genus Centaurea is known to contain a variety of secondary metabolites of various types, especially sesquiterpene lactones and flavonoids, which have been shown to be biologically active [1][2][3].Centaurea lippii L. (Asteraceae), synonyms Volutaria lippii (L.) Cass.; Volutarella lippii (L.) Cass.; Amberboa lippii (L.) DC., is widely distributed in all Mediterranean areas [4]. Previous phytochemical investigation of this species has led to the isolation of sesquiterpene lactones [5]. The present work concerned the phytochemical study of the chloroform and the n-butanolic soluble parts of the aqueous ethanol extract of the leaves and flowers of the Algerian species.Centaurea lippii was collected during the flowering phase in May 1998, in the East of Algeria, and was authenticated by Prof. A. Kaabeche (Biology Department, University of Setif Algeria).Air-dried and powdered leaves and flowers (1267 g) of Centaurea lippii were macerated with EtOH for 24 h three times. After filtration, the filtrates were combined, concentrated at room temperature, and diluted with 800 mL H 2 O. After remove of chlorophyll, the remaining aqueous solution was extracted successively with CHCl 3 , EtOAc, and n-BuOH to obtain the extracts: chloroform (12 g), ethyl acetate (1 g), and n-BuOH (16 g).The chloroform extract was chromatographed on a 70-230 mesh silica gel column eluted with a gradient of chloroformacetone to yield 8 fractions from which the most important compound 1 was isolated and purified by preparative TLC on silica gel using chloroform-acetone-EtOAc (1:1:3) as eluent.The n-BuOH extract was applied to a polyamide SC6 column eluted with a gradient of toluene-MeOH to yield 9 fractions. Three flavonoid glycosides 2-4 contained in several fractions were isolated by preparative TLC using water-MeOHmethyl-ethyl ketone-acetylacetone (13:3:3:1) as solvent. Purification of each compound for spectral analysis was carried out using MeOH over Sephadex LH-20 column [6].The structures were elucidated by IR, UV, 1 H NMR, 13 C NMR, and MS analysis. All these data were in good agreement with the respective literature data [6][7][8][9][10].Compound 1. C 20 H 26 O 7 , mp 143°C. IR spectrum (KBr, Q, cm -1 ): 1759 (J-lactone), 1705 (C=O conjugated ester), 3356 (-OH). 1 H NMR (250 MHz, CDCl 3 + 2 drops of CD 3 OD, G, ppm, J/Hz): 4.78 (1H, m, H-1), 2.20 (1H, m, H-2), 2.25 (1H, m, H-2c), 2.55 (1H, m, H-3), 2.00 (1H, m, H-3c), 4.81 (1H, d, J 5-6 = 9.7, H-5), 5.25 (1H, t, J 6-5 = J 6-7 = 9.7, H-6), 3.12 (1H, m, H-7), 5.15 (1H, m, H-8), 2.50 (1H, m, H-9), 2.55 (1H, m, H-9c), 5.67 (1H, d, J 13-7 = 2.7, H-13), 6.14 (1H, d, J 13c-7 = 3.3, H-13c), 1.47 (1H, s, H-14), 3.99 (1H, d, J 15-15c = 13.9, H-15), 4.23 (1H, d, J 15c-15
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