Identification and in vitro anti-esophageal cancer activity of a series of halogenated monoterpenes isolated from the South African seaweeds Plocamium suhrii and Plocamium cornutum

► Plocamium suhrii produces a number of unusual halogenated monoterpenes based on a regular monoterpene skeleton. ► These compounds show moderate in vitro cytotoxicity toward esophageal cancer cells. ► Selected halogenated monoterpenes isolated from South African Plocamium spp may be used as taxonomic markers.