Flavonoid constituents of Sideritis caesarea

Abstract

The acetone extract of the aerial parts of Sideritis caesarea Duman, Aytac & Baser (Lamiaceae) afforded the flavonoids penduletin (1) and apigenin (2) and 6 glycosylated flavonoids, 4--O-methyl-isoscutellarein-7-O-[6 --O-acetyl-beta-D-allopyranosyl-(1 -> 2)]-6 --O-acetyl-beta-D-glucopyranoside (3), 4--O-methylhypolaetin-7-O-[6 --O-acetyl-beta-D-allopyranosyl-(1 -> 2)]-6 --O-acetyl-beta-D-glucopyranoside (4), isoscutellarein-7-O-[6 --O-acetyl-beta-D-allopyranosyl-(1 -> 2)]-6 --O-acetyl-beta-D-glucopyranoside (5), isoscutellarein-7-O-[6 --O-acetyl-beta-D-allopyranosyl-(1 -> 2)]-beta-D-glucopyranoside (6), 4--O-methylhypolaetin-7-O-[6 --O-acetyl-beta-D-allopyranosyl-(1 -> 2)]-beta-D-glucopyranoside (7), and hypolaetin-7-O-[6 --O-acetyl-beta-D-allopyranosyl-(1 -> 2)]-beta-D-glucopyranoside (8). The compounds were identified by the use of 1D- and 2D-NMR and UV spectroscopic techniques and by comparisons with the reported data. The acetyl-cholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory activities of the acetone, methanol, and water extracts of the plant and of the flavones penduletin and apigenin were evaluated at 200 mu g/mL. The water extract exhibited better activity against the enzyme AChE as compared to both the acetone and the methanol extracts. Penduletin (1) showed significant activity against BChE (66.58%) while apigenin (2) showed weak activity against both enzymes.