New sesquiterpenes from the soft coral Litophyton arboreum

Abstract Two new sesquiterpenes; 8α,11-dihydroxy-β-cyperon ( 2 ), and 5- epi -7α-hydroxy-( +)-oplopanone ( 3 ), were isolated from the soft coral Litophyton arboreum, together with nine known ones, including five sesquiterpenes; 11-hydroxy-8-oxo-β-cyperon ( 1 ), alismoxide ( 4 ), 5β,8β-epidioxy-11-hydroxy-6-eudesmene ( 5 ), chabrolidione B ( 6 ), 7-oxo-tri-nor-eudesm-5-en-4β-ol ( 7 ), two sterols; 7β-acetoxy-24-methyl-cholesta-5,24(28)-diene-3β,19-diol ( 8 ), nebrosteroid M ( 9 ), and two glycerol derivatives; chimyl alcohol ( 10 ) and batyl alcohol ( 11 ). The structures of the isolated compounds were characterized using spectroscopic techniques, predominately HR-ESI–MS, 1D, 2D-NMR, and ECD analyses. Compounds 1 – 11 were evaluated for their cytotoxic activity against three human cancer-cell lines (A549, MCF-7 and HepG2), and anti-leishmanial potential against the causal parasite, Leishmania major. Compounds 4 , 8 , and 9 exhibited potent cytotoxic activity against the A549 cell line (IC 50 = 17.0 ± 2.5, 13.5 ± 2.1, and 16.5 ± 1.3 μg/ml, respectively) as compared with the standard antitumor agent etoposide (IC 50 28.4 ± 4.5 μg/ml). In addition, compound 9 exhibited remarkable cytotoxic activity against MCF-7 cell line (IC 50 = 24.7 ± 2.1 μg/ml: 22.2 ± 4.2 μg/mL for etoposide). Graphical abstract