Six new (3Z,5E)-11,20-epoxybriara-3,5-dien-7,18-olide diterpenoids, gemmacolides N–S (1–6), were isolated together with four known analogues, juncenolide D, and juncins R, S and U (7–10), from the South China Sea gorgonian Dichotella gemmacea. The structures of the new compounds were elucidated by the detailed analysis of spectroscopic data in combination with the comparison with reported data. The absolute configuration of 1 was determined by a TDDFT calculation of its solution ECD spectrum, affording the determination of absolute configuration of other analogues by simply comparing their ECD spectra with that of 1. The cytotoxic and antimicrobial activities of these compounds were evaluated. In preliminary in vitro bioassays, compounds 4, 5, 6, 8 and 9 showed cytotoxicity against A549 and MG63, while compounds 1, 2, 4, 7–10 showed antimicrobial activity against the fungus Septoria tritici and the bacterium Escherichia coli.
Seven new briarane diterpenoids, gemmacolides G-M (1-7), were isolated together with two known analogues, juncin O and junceellolide C, from the South China Sea gorgonian Dichotella gemmacea. The structures of the new compounds were elucidated by detailed analysis of spectroscopic data and comparison with reported data. In an in vitro bioassay, these compounds exhibited different levels of growth inhibition activity against A549 and MG63 cells. In particular, compound 4 was more active than the positive control adriamycin against A549 cells. Compounds 4 and 7 also exhibited weak antimicrobial activity against the bacterium Bacillus megaterium and the fungus Septoria tritici, respectively.
Two new triterpene glycosides, scabraside A (1) and B (2), and a structurally known compound (3), were isolated from the sea cucumber Holothuria scabra (Holothuriidae) collected from the South China Sea. Structure of these compounds was elucidated by spectroscopic and chemical methods. The glycosides 1 and 2 exhibit the same common structural features, i. e., the presence of 12- and 17-hydroxy groups in the holostane-type triterpene aglycone with a 9(11)-ene bond, but are different in the side chains of the triterpene aglycone. The glycosides 1 and 2 had significant in vitro cytotoxicity against four human tumor cell lines in comparison to 10-hydroxycamptothecin.
Eighteen new 11,20-epoxy-3Z,5E-dien briaranes, gemmacolides AA–AR (1–18), were isolated together with three known analogs, dichotellides F (19) and I (20), and juncenolide C (21), from the South China Sea gorgonian Dichotella gemmacea. The structures of the compounds were elucidated by detailed spectroscopic analysis and comparison with reported data. The absolute configuration was determined based on the ECD experiment. In the in vitro bioassay, compounds 1–3, 5, 6, 8–12, and 14–19 exhibited different levels of growth inhibition activity against A549 and MG63 cell lines. Preliminary structure-activity analysis suggests that 12-O-isovalerate may increase the activity whereas 13- or 14-O-isovalerate may decrease the activity. Contribution of substitutions at C-2 and C-16 remains uncertain.
Seven new briarane diterpenoids, gemmacolides AS-AY (1–7), were isolated together with ten known analogues (8–17) from the South China Sea gorgonian Dichotella gemmacea. The structures of the new compounds were elucidated by the detailed analysis of spectroscopic data and comparison with reported data. The absolute configuration of compounds was determined based on electronic circular dichroism (ECD) experiments and genetic correlations as well. Compounds 15 and 16 were reported for the first time for the gorgonian. In the preliminary in vitro bioassays, compound 5 showed potential growth inhibitory activity against MG63 cells.
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