Monomeric and Dimeric Bromophenols from the Red Alga Ceramium Sp. with Antioxidant and Anti-Inflammatory Activities

LC-MS²-based molecular networking using the Global Natural Products Social (GNPS) tool revealed a rich assortment of brominated compounds present in the antioxidant fraction of a red algal extract (Ceramium sp.) Further chemical investigation led to discovery of one monomeric bromophenol (lanosol isopropyl ether, 1) and seven dimeric ones (bromourceolatols A-G, 2-8), all of which are previously undescribed. Their structures were elucidated by extensive analysis of their spectroscopic data. Compounds 2-8 were determined to be racemic trans-type isomers by NOESY, specific optical rotation, and ECD. Compounds 1 and 3 displayed antioxidant activity with their EC₅₀ of 44.4 and 47.0 μM, respectively, for scavenging DPPH free radicals while compounds 2 and 4 had approximate EC₅₀ values of ~ 64 μM. Furthermore, compounds 2, 3, and 7 exhibited relatively potent anti-inflammatory activity at 32 μM by quenching 97%, 47%, and 73% of nitric oxide induced by bacterial lipopolysaccharide in macrophage RAW264.7 cells, respectively.