Abstract
Three new polyoxygenated steroids, michosterols A–C (1–3), and four known compounds (4–7) were isolated from the ethyl acetate (EtOAc) extract of the soft coral Lobophytum michaelae, collected off the coast of Taitung. The structures of the new compounds were elucidated on the basis of spectroscopic analyses and comparison of the nuclear magnetic resonance (NMR) data with related steroids. The cytotoxicity of compounds 1–3 against the proliferation of a limited panel of cancer cell lines was assayed. Compound 1 was found to display moderate cytotoxicity against adenocarcinomic human alveolar basal epithelial (A549) cancer cells. It also exhibited potent anti-inflammatory activity by suppressing superoxide anion generation and elastase release in N-formyl-methionyl-leucyl-phenylalanine/cytochalasin B (fMLP/CB)-stimulated human neutrophils. Furthermore, 3 could effectively inhibit elastase release, as well.
Highlights
Previous chemical investigations on the octocorals of the genus Lobophytum have led to the isolation of structurally unique steroids [1,2,3,4,5,6], some of which have been shown to exhibit cytotoxic [2,3,5,6] and anti-inflammatory [2,5] activities
The 1 H nuclear magnetic resonance (NMR) spectrum in conjunction with the heteronuclear single quantum coherence (HSQC) spectrum revealed the presence of eight methyl groups (δH 2.03 (3H, s), 1.50 (3H, s), 1.41 (3H, s), 1.31 (3H, s), 0.96 (6H, s), 0.93 (3H, d, J = 6.8 Hz) and 0.88 (3H, d, J = 7.2 Hz)), an olefinic methine proton (δH 5.70 (1H, d, J = 2.0 Hz)) and a hydroperoxy group signal at δH 8.06
The results showed that only compound exhibited a moderate cytotoxicity effect against the
Summary
Previous chemical investigations on the octocorals of the genus Lobophytum have led to the isolation of structurally unique steroids [1,2,3,4,5,6], some of which have been shown to exhibit cytotoxic [2,3,5,6] and anti-inflammatory [2,5] activities. For the purpose of searching for bioactive compounds, we have previously investigated the chemical constituents of soft corals of the genus. Previous investigations have that shown softLobophytum coral Lobophytum michaelae produce bioactive cembranolides with cytotoxicity towards cancer cancer cell lines. Figures and comparison of spectroscopic data ofcompounds the new compounds of the reported structurally-related compounds have allowed us to establish the structures of 1–3. C-16 and and an an uncommon uncommon olefinic structure hydroperoxyl group at C-20, whereas 2 has this group at C-16
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