Secondary metabolites of microalgae

Microalgae are varied group of photosynthetic organisms, exist in different habitats such as freshwater, marine, brackish, polar regions, acidic/alkali waters, hot water springs, and wastewaters. Microalgae produce secondary metabolites as an adaptive mechanism to thrive in extreme environments. In recent years the bioprospecting of microalgae from different habitats opened up a wide scope for identification of new metabolites and understanding the mechanism of their synthesis, bioactivities, and applications. In addition, the advancements in culturing methods and techniques are contributing to the exploration of new species having metabolites of commercial importance. The secondary metabolites are of varied chemical nature viz., isoprenoids (carotenoids, terpenoids, sterols), polyketides, amino-acid-derived natural products, phenolic compounds, polyunsaturated fatty acids, etc. The secondary metabolites found importance in nutraceutical, therapeutic, and biological activities. The present chapter discusses the current status of various microalgal secondary metabolites and their commercial applications.