Two New Chromane Meroditerpenoids with Anti-Neuroinflammatory Potential from a Chinese Collection of the Brown Alga <i>Sargassum siliquastrum</i>

Objectives: This study focused on the isolation, structural elucidation, and anti-neuroinflammatory activities of meroditerpenoids from a Chinese collection of the brown alga Sargassum siliquastrum. Methods: A variety of chromatographic methods were applied to isolate compounds from the EtOAc-soluble extract of S. siliquastrum. Their chemical structures were determined by extensive spectroscopic analyses, including 1D and 2D NMR and HR-ESI-MS data. The compounds were evaluated for their anti-neuroinflammatory activities against lipopolysaccharide (LPS)-induced inflammatory response in murine BV-2 microglial cells. Results: Two new chromane-type meroditerpenoids, namely 9′-deoxysargachromanol E (1) and 3′,4′-dihydro-4′-hydroxysargachromanol I (2), were isolated from the EtOAc-soluble extract of S. siliquastrum, along with three known analogues (3–5). Compounds 1–4 showed inhibition against LPS-induced nitric oxide (NO) production in BV-2 cells with IC 50 values of 19.5, 8.0, 15.1, and 14.3 μM, respectively. Conclusions: Two new chromane meroditerpenoids were identified from the brown alga S. siliquastrum. These meroditerpenoids had promising anti-neuroinflammatory effects in vitro.