New meroterpenoids and C-methylated flavonoid isolated from Baeckea frutescens

Phytochemical investigation of the aerial parts of Baeckea frutescens resulted in the isolation of three new mono- or sesquiterpene-based meroterpenoids, frutescones S−U ( 1 − 3 ), and one pair of new (±)-5,7-dihydroxy-8-isobutyryl-6-methyldihydroflavonol ( 4 ). Their structures and absolute configurations were established by HR-ESI-MS, 1D and 2D NMR, and quantum chemical ECD calculation. Compound 1 exhibited inhibitory effect on NO production in LPS-activated RAW 264.7 macrophages with an IC₅₀ value being 0.81 µmol·L^–1.