Flavonoids from Knautia montana flowers growing in Azerbaijan

Abstract

The family Dipsacaceae (teasel) comprises 10 genera and about 300 species that are distributed mainly in Mediterranean and Western Asian countries. The genus Knautia L. is one of the genera in this family. It is represented by two species in the flora of Azerbaijan, K. montana (M.B.) D.C. and K. involucrate Somm. et Lev [1]. K. montana is the most widely distributed species, is a biennial or perennial plant, and reaches 100–150 cm in height. Isolation of Flavonoids from K. montana Flowers. Air-dried flowers (1.2 kg) were collected on July 11, 2009, below Budug village, Gubin Region, Azerbaijan Republic and were extracted with EtOH (95%, 3 , 1:8) at room temperature. The extracts were filtered, evaporated in vacuo to 200–250 mL, diluted with H2O (300 mL), and evaporated to an aqueous residue. The aqueous solution was extracted with hexane, EtOAc:hexane (1:1.5), and EtOAc. The EtOAc:hexane extract was evaporated. The solid was recrystallized from CHCl3:MeOH to afford 1. The EtOAc extract was evaporated to dryness. The solid was dissolved in hot H2O and left overnight. The resulting crystals were separated to afford 2. The filtrate was evaporated. The solid was recrystallized from EtOH to afford 3. Compound 1, C15H10O5, mp 345–346°C (CHCl3:MeOH). UV spectrum (MeOH, max, nm): 268, 335. Yellow crystals, soluble in alcohols and acetone, insoluble in hexane and H2O. Rf 0.90 (n-BuOH:AcOH:H2O, 4:1:5). Bryant’s cyanidin test indicated that the aglycon was a flavonoid. These data and direct comparison with an authentic sample identified 1 as apigenin. Compound 2, C22H22O11, mp 260–262°C (H2O). UV spectrum (MeOH, max, nm): 245, 260, 344; +CH3COONa: 268, 404; +AlCl3: 274, 300, 336, 428. Yellow crystals, soluble in DMF and Py, insoluble in alcohol, poorly soluble in H2O. Fluoresces in filtered UV light as dark spots. The compound under normal conditions (5% H2SO4, 10 h) is not hydrolyzed. Kiliani acid hydrolysis formed 7-O-methylluteolin and D-glucose [2–5], which indicated that the studied compound was a C-glucoside. This was also confirmed by NMR spectra (Table 1). PMR and 13C NMR spectra of 2 were interpreted as the structure shown below. Swertiajaponin, 7-O-methylluteolin-6-C-D-glucopyranoside, had an identical structure [6].