New dihydrophenanthrenes from Elatostema tenuicaudatum

Three new dihydrophenanthrenes were isolated from the whole plant of Elatostema tenuicaudatum collected in Vietnam. These compounds were identified as 2,3,5-trihydroxy-9,10-dihydrophenanthrene (1), 2-methoxy-5-hydroxy-9,10-dihydrophenanthrene 3-O-β-D-glucopyranoside (2), and 2,5-dihydroxy-9,10-dihydrophenanthrene 3-O-β-D-glucopyranoside (3). Their structures were determined by HR-ESI-MS and 1D, 2D NMR spectroscopy. Furthermore, the inhibitory activities of these compounds against nitric oxide (NO) production in lipopolysaccharide-activated RAW264.7 cells were evaluated. Compound 1 exhibited significant inhibition of NO production, with an IC₅₀ value of 15.8 ± 1.2 µM. This study represents the first report on the chemical compositions and biological activities of E. tenuicaudatum.