The present study is aimed at identification of bioactive compounds and their pharmacological properties four macro-algae (Hydropuntia edulis, Halymenia venusta, Ulva lactuca Padina gymnospora) from the Hare Island, Tuticorin district Tamil Nadu, India. characterization ethanol extracted was done using GC-MS techniques. major secondary metabolites such as alkaloids, phenol, saponins, flavonoids...