Five new cembrane-type diterpenes, lobocalines A–E (
1–
5), and four new steroids, lobocaloids A–D (
9–
12), along with six known related compounds (
6–
8 and
13–
15) were isolated from the Yalong Bay
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Five new cembrane-type diterpenes, lobocalines A–E (
1–
5), and four new steroids, lobocaloids A–D (
9–
12), along with six known related compounds (
6–
8 and
13–
15) were isolated from the Yalong Bay soft coral
Lobophytum catalai Tixier-Durivault. The structures of the new compounds were elucidated by extensive spectroscopic analysis, NMR calculation with DP4+ analysis, time-dependent density functional theory–electronic circular dichroism (TDDFT-ECD) calculations, X-ray diffraction analyses and comparison with the reported spectroscopic data of known compounds. Further, with the aid of X-ray diffraction analysis, the structure of lobocrasol B (
15) was firmly revised as
15a. In in vitro bioassays, compound
2 showed moderate antibacterial activities against fish pathogenic bacteria
Streptococcus parauberis KSP28 and
Phoyobacterium damselae FP2244 with minimum inhibitory concentration (MIC) values of 8.7 and 17.3 µg/mL, respectively. All the steroids exhibited antibacterial activities against the
S. parauberis KSP28 with MIC values ranging from 12.3 to 53.6 µg/mL. Compounds
2,
7 and
14 have remarkable inhibitory effects on the hemolysin production of
Staphylococcus aureus, while compounds
8–
12 have medium inhibitory effects on the pyocyanin production in
Pseudomonas aeruginosa.
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