Megastigmane glycosides from Urena lobata

Five new megastigmane glycosides, urenalobasides A-E (1-5), together with 11 known ones (6-16) were isolated from Urena lobata. Their structures were determined by extensive spectroscopic and spectrometric data (1D and 2D NMR, IR, and HRESIMS) and calculated electronic circular dichroism method. Compounds 1 and 2 are two unusual megastigmanes structurally containing a 6/5 fused ring system. Compound 3 exhibits inhibition of nitric oxide production in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophage cells with IC₅₀ value of 53.7 ± 1.0 μM (positive control, dexamethasone, IC₅₀ = 16.6 ± 0.8 μM).