A new cyclohexenone and two new phenanthrones from Elatostema tenuicaudatum.

A new cyclohexenone, 5S-(3,4-dihydroxyphenethyl)cyclohex-2-en-1-one (1), along with two new phenanthrones, (4aS,10aS)- 1,9,10,10a -tetrahydro-4a,6,7-trihydroxy-4(4aH)-phenanthrone (2) and (4aS,10aS)-4a-hydroxy-7-methoxy-1,9,10,10a-tetrahydro-4(4aH)-phenanthrone 6-O-β-D-glucopyranoside (3) were isolated from the whole plant of Elatostema tenuicaudatum. The structures were determined by spectroscopic methods including 1D, 2D NMR and HR-ESI-MS. The absolute configurations of compounds 1-3 were determined by their experimental and calculated ECD spectral data. The isolates were evaluated for inhibitory activity on nitric oxide (NO) production in lipopolysaccharide (LPS)-activated RAW 264.7 macrophage cells, and compound 2 showed the strongest activity with an IC50 value of 9.5 ± 1.2 μM.