New flavonoids and methylchromone isolated from the aerial parts of Baeckea frutescens and their inhibitory activities against cyclooxygenases-1 and -2

In the present study, we carried out a phytochemical investigation of the ethanol extract of the aerial parts of Baeckea frutescens, which resulted in the isolation of two new flavonoid glycosides, myricetin 3-O-(5"-O-galloyl)-α-L-arabinofuranoside ( 1 ), 6-methylquercetin 7-O-β-D-glucopyranoside ( 2 ), one new methylchromone glycoside, 7-O-(4', 6'-digalloyl)-β-D-glucopyranosyl-5-hydroxy-2-methylchromone ( 3 ), together with three known compounds ( 4 - 6 ). The structures of these isolated compounds were established on the basis of 1D and 2D NMR techniques and chemical methods. The anti-inflammatory activities of the compounds 1 - 6 were evaluated for their inhibitory effects against cyclooxygenases-1 and -2 in vitro. Compounds 1 - 6 showed potent COX-1 and COX-2 inhibiting activities in vitro with IC₅₀ values ranging from 1.95 to 5.54 μmol·L^-1 and ranging from 1.01 to 2.27 μmol·L^-1, respectively.