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

Abstract

Abstract Five new D ‐ring‐opened phragmalin‐type limonoids, tabulalins A–E ( 1 – 5 , 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) δ ‐lactone ring) of phragmalins was cleaved, and rare C(16)/C(30) δ ‐lactone ring in 1 – 3 or C(16)/C(8) γ ‐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 IC 50 values of 15.3±0.6, 13.0±0.5, and 17.1±0.7 μ M , respectively.