New flavonoids from Campylotropis hirtella with immunosuppressive activity

In an effort to identify natural compounds with immunosuppressive activity, nine new flavonoids, including one isoflav-3-ene derivative (1), one coumaronochromone (2), two isoflavanones (3, 4), one isoflavone derivative (6), one isoflavone (7), three flavonols (8, 9, 10), as well as one known compound, hydroisoflavone C (5), were isolated from the roots of Campylotropis hirtella. The structures of these compounds were elucidated by extensive spectroscopic measurements. All of the compounds were assessed for immunosuppressive activity. Among the isolates, compound 2 showed good inhibitory activity against mitogen-induced splenocyte proliferation with an IC₅₀ of 0.28 μM and relatively low cytotoxicity.