Flavonoids from Anoectochilus annamensis and their Anti-inflammatory Activity

One new flavonol diglycoside, 4′,5-dihydroxy-3,3′,7-trimethoxyflavone 4′- O-α-L-rhamnopyranosyl-(1→6)-β-D-glucopyranoside (1), and two known compounds (2–3) were isolated from the methanol extract of Anoectochilus annamensis Aver. aerial parts. The effects were evaluated of all isolated compounds (1–3) on LPS-induced production of the inflammatory mediator nitric oxide (NO) by RAW264.7 cells. 4′,5-Dihydroxy-3,3′,7-trimethoxyflavone (2) was the most active while the addition of a rutinoside at C-4′ (compound 1) decreased the inhibitory activity. This is the first report on the chemical composition and biological activity of A annamensis.