Structure determination and quantification of a new flavone glycoside with anti-acetylcholinesterase activity from the herbs of Elsholtzia ciliata

Three acacetin triglycosides (compounds 1, 2 and 3) were isolated from the herbs of Elsholtzia ciliata (Labiatae). The structure were identified as 7-O-beta-D-glucopyranosyl-(1 -> 2)[alpha-L-rhamnopyranosyl-(1 -> 6)]-beta-D-glucopyranoside (compound 1), 7-O-(6-O-acetyl)-beta-D-glucopyranosyl-(1 -> 2)[alpha-L-rhamnopyranosyl-(1 -> 6)]-beta-D-glucopyranoside (compound 2) and 7-O-(6-O-acetyl)-beta-D-glucopyranosyl-(1 -> 2)[(4-O-acetyl)-alpha-L-rhamnopyranosyl-(1 -> 6)]-beta-D-glucopyranoside (compound 3) of acacetin. The structures of these compounds were determined on the basis of 2D-NMR spectroscopic data. Compound 3 has not been isolated from a natural source. In addition, the three compounds were quantitatively analysed by HPLC. Acetylcholinesterase (AChE) inhibition activity was assayed to find anti-Alzheimer's activity, since this enzyme increases the concentration of acetylcholine (ACh), a neurotransmitter, responsible for brain's memory. Acacetin, the aglycone of the three compounds, exhibited a potent anti-cholinesterase activity (IC50, 50.33 +/- 0.87), though its glycosides (1, 2 and 3) were less active. HPLC analysis demonstrated that the three compounds were contained in the MeOH extract in the order of compounds 2 (12.63 mg/g extract) > 3 (3.10 mg/g) > 1 (2.92 mg/g). [GRAPHICS] .