Study on the chemical constituents and biological activity of soft coral Sinularia sp.

The chemical constituents of the soft coral Sinularia sp. collected off Ximao Island in the South China Sea were isolated by comprehensively utilizing various separation techniques such as thin-layer chromatography, silica gel column chromatography, octadecylsilane reverse phase column chromatography, Sephadex LH-20 column chromatography, and high-performance liquid chromatography (HPLC). The planar structure and stereochemistry of the isolated compounds were determined by nuclear magnetic resonance (NMR), mass spectrometry (MS), infrared spectroscopy (IR), and quantum chemical calculations. Six compounds were isolated from the titled soft coral and identified as (3R, 6S)-3-((R)-sec-butyl)-6-isopropylmorpholine-2, 5-dione (1), oculatolide (2), octahydro-4-hydroxy-3R-methyl-7-methylene-R-(1-methylethyl)-1H-indene-1-methanol (3), ent-4(15)-eudesmene-1β, 6α-diol (4), 5-epi-eudesm-4(15)-ene-1β, 6β-diol (5), and ergosterol peroxide (6), respectively. Among them, compound 1 was characterized as a new morpholine derivative, and compounds 3-5 were isolated for the first time from this genus of soft corals. In terms of biological activity, compounds 1-6 underwent screening for antibacterial, anti-inflammatory, and anti-cancer activities, compounds 2 and 6 exhibited significant and broad-spectrum antimicrobial activity, while compound 2 also showed potent anti-inflammatory (IC₅₀ = 5 ± 0.03 mmol·L^-1) and strong anti-proliferative activity against human non-small cell lung cancer cells (A549) and human colorectal adenocarcinoma cells (HT-29) with IC₅₀ values of 17.27 ± 2.32 and 14.14 ± 0.72 mmol·L^-1, respectively.