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A new diterpenoid with an unusual capnosane skeleton, sinuhumilol A (1), alone with twelve known diverse compounds (2–13), were isolated from the South China Sea soft coral Sinularia humilis. Their structures and stereochemistry were elucidated by extensive spectroscopic analysis, quantum chemical calculations, and/or by the comparison of the spectroscopic data with those reported in the literature. In bioassay, compound 11 exhibited interesting specific cytotoxicity against the human colon adenocarcinoma cell line HT-29 with IC50 value of 12.5 µM. [ABSTRACT FROM AUTHOR]

Main observation and conclusion: A detailed chemical study on the Hainan soft coral Sinularia crass has resulted in the isolation and characterization of eleven casbane‐type diterpenoids, named sinucrassins A—K (1—11), along with six known related ones (12—17). Their structures were elucidated by extensive spectroscopic analyses and comparison with the reported data. The absolute configurations of new compounds were determined by the X‐ray diffraction analysis and computer‐assisted structural elucidation including 13C NMR data calculation and time‐dependent density functional theory/electronic circular dichroism calculation. [ABSTRACT FROM AUTHOR]

A detailed chemical investigation of the South China Sea soft coral Sarcophyton ehrenbergi has yield seven undescribed cembranoids, namely isoehrenbergol D and sarcoehrenolides F–K embodying a rare α , β -unsaturated-lactone moiety at C-6 to C-19, along with two known related compounds, ehrenbergol D and sarcoehrenolide A. Their structures and absolute configurations were unambiguously established in the light of extensive spectroscopic data analysis, modified Mosher's method, X-ray diffraction analysis, and quantum chemical computation method. In a bioassay for α -glucosidase inhibition, ehrenbergol D was evaluated as α -glucosidase inhibitor with an IC 50 value of 13.57 μM. Seven undescribed cembranoids and two known analogs were isolated and identified from the soft coral Sarcophyton ehrenbergi. The α -glucosidase inhibitory activity of these compounds was evaluated. [Display omitted] • Seven undescribed cembranoids were isolated from the soft coral Sarcophyton ehrenbergi. • Those cembranoids featured a rare α , β -unsaturated-lactone moiety at C-6 to C-19. • Ehrenbergol D was evaluated as α -glucosidase inhibitor with an IC 50 value of 13.57 μM. [ABSTRACT FROM AUTHOR]

[Display omitted] • Seven novel casbane diterpenoids were isolated from Sinularia erecta. • Sinuereperoxides B and C are two rare casbane diterpenoids with an uncommon 8,10-peroxide bridge. • The quantum chemical calculations and X-ray diffraction analysis were applied to determine absolute configurations. • Anti-inflammatory activity by the inhibition of TNF-α release was evaluated. A further systematically chemical investigation of the South China Sea soft coral Sinularia erecta led to the discovery of two rare casbane diterpenoids with an uncommon 8,10-peroxide bridge, sinuereperoxides B (1) and C (2), five new casbanes with other oxygenated patterns (3 – 7), and seven known casbanes (8 – 14). The structures and absolute configurations of 1 – 7 were established by extensive spectroscopic data analyses, X-ray diffraction analysis, and/or quantum chemical calculations. In bioassay, compounds 2 , 7 , 11 and 12 exhibited considerable anti-inflammatory activity by the inhibition of TNF-α release, with IC 50 values of 33.8 μM, 5 μM, 9.9 μM and 8 μM. [ABSTRACT FROM AUTHOR]

• Four new cembranoids were isolated from the soft coral Sinularia crassa. • Providing solid proof to challenge the widely accepted B. Tursch's empirical rule. • (+)- 2 and 5 were α -glucosidase inhibitors without cytotoxicity towards LO2 cells. A detailed chemical research of the soft coral Sinularia crassa collected from the South China Sea yielded a series of cembrane-type diterpenoids, including four new cembranoids, namely sinulacrassins A − C (1 , (+)- 2 , (+)- 4) and ent -xishaflavalin G ((+)- 3) , along with five known analogs ((-)- 3 , 5 – 8). Their structures were elucidated by detailed spectroscopic analysis, chemical methods, and the comparison with those literature data. The absolute configuration of 1 was established by time-dependent density functional theory electronic circular dichroism (TDDFT/ECD) calculation, and the absolute configuration of (+)- 2 was determined using the modified Mosher's method. The bioassay results revealed that (+)- 2 and 5 were novel α -glucosidase inhibitors with IC 50 values of 10.65 ± 0.16 and 30.31 ± 1.22 μM, respectively. In addition, (+)- 2 and 5 were nontoxic towards human normal hepatocyte (LO2) cells at 100 μM. The present results highlighted the unusual coexistence of α and β configurations of C-1 in cembranoids from soft coral in the Order Alcyonacea, and provided new chemotype for the development of α -glucosidase inhibitors used in anti-diabetes treatment. [ABSTRACT FROM AUTHOR]