Two New Cembranoids From the Soft Coral <i>Sinularia</i> Sp. With Antioxidant Activity

The chemical investigation of diethyl ether-soluble partition of the acetone extract of soft coral Sinularia sp. collected off Ximao Island, has led to the isolation and characterization of two new cembranoids (1 and 2), along with one known related analog (3). The structures and absolute configurations of 1 and 2 were elucidated through extensive spectroscopic analysis and time-dependent density functional theory-electronic circular dichroism calculations. The antioxidant capacity of those isolated compounds was evaluated by total reducing power assay, 2,2-diphenyl-1-picrylhydrazyl assay, and 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) scavenging assay. Compounds 1 and 2 exhibited good antioxidant activity, especially 2, which was superior to that of the positive control vitamin C. In vitro cytotoxicity assay showed that compounds 1-3 had no significant effect on the cell viability of MV-4-11 cells and A549 cells at a concentration of 50 µM.