D-Ring-Opened Phragmalin-Type Limonoids from Chukrasia tabularis var. velutina

Five new D-ring-opened phragmalin-type limonoids, tabulalins AE (15, resp.), were isolated from the stem bark of Chukrasia tabularis var. velutina. In the structures of these new isolates, the D-ring (C(16)/C(17) d-lactone ring) of phragmalins was cleaved, and rare C(16)/C(30) d-lactone ring in 13 or C(16)/C(8) ?-lactone ring in 4 and 5 were formed. The structures of these new compounds were elucidated based on extensive 1D- and 2D-spectroscopic analyses (HSQC, HMBC, and ROESY) and HR-ESI-MS. The major compounds, 2, 3, and 5, were evaluated for their inhibitory activities against lipopolysaccharide (LPS)-induced nitric oxide (NO) production in a macrophage (RAW264.7) cell line with IC50 values of 15.3 +/- 0.6, 13.0 +/- 0.5, and 17.1 +/- 0.7 mu M, respectively.