<jats:p>Four new sulfated sesquiterpene hydroquinones siphonodictyals E1–E4 (<jats:bold>1</jats:bold>–<jats:bold>4</jats:bold>) and cyclosiphonodictyol A (<jats:bold>5</jats:bold>) were isolated from a sample of the Caribbean sponge <jats:italic>Aka coralliphagum</jats:italic> collected off the coast of San Salvador in the Bahamas. The structures of the new compounds were elucidated on the basis of mass spectrometric and NMR spectroscopic analysis. Compounds <jats:bold>1</jats:bold>–<jats:bold>4</jats:bold> are derivatives of siphonodictyal E (<jats:bold>9</jats:bold>). Siphonodictyal E4 (<jats:bold>4</jats:bold>) exhibited mild antiproliferation activity against L929 mouse fibroblast, KB-31 epidermoid carcinoma, and MCF-7 breast cancer cell lines, while siphondictyal E3 (<jats:bold>3</jats:bold>) and cyclosiphonodictyol A (<jats:bold>5</jats:bold>) showed moderate activity against Gram-positive bacteria.</jats:p>