Many algae produce antibiotics such as acrylic acid found in Phaeocystis poucht. This anti­biotic inhibits the growth of gram-positive organisms. The phenols found in macro — and microalgae have antimicrobial activity.

The microalga Scenedesmus obliquus has been used in postoperative recovery, assisting in coagulation of the skin surface. The extracts of the diatom Asterionella notata have an antifun­gal and antiviral activity. Toxic algae have been used as a depressant vessel, similar to tetro — dotoxin found in fish (Richmond, 1990).

Another drug obtained from microalgae is phycocyanin, a natural antioxidant that, when combined with caloric restriction, can contribute to mitigating the aging process. Free radicals are partly responsible for the human aging process (Finkel, 2003). The oxidative damage caused by free radicals has been linked to several diseases such as heart disease, atheroscle­rosis, lung problems, Alzheimer’s, and Parkinson’s. The DNA damage caused by free radicals plays an important role in the processes of mutagenesis and carcinogenesis.