Marine and freshwater microalgae as a sustainable source of cosmeceuticals

A prominent feature of stress-tolerant microalgae is their versatile metabolism, allowing them to synthesize a broad spectrum of molecules. In microalgae, they increase stress resilience of these organisms. In human body, they exhibit anti-aging, anti-inflammatory, and sunscreen activities. This is not surprising, given that many of the stress-induced deleterious processes in human body and in photosynthetic cell are mediated by the same mechanisms: free-radical attacks and lipid peroxidation. It is also worth noting, that the photosynthetic machinery of microalgae is always at risk of oxidative damage since high redox potentials and reactive molecules are constantly generated during its functioning. These risks are kept at bay by efficient reactive oxygen species elimination systems including, inter alia, potent lowmolecular antioxidants. Therefore, photosynthetic organisms are a rich source of bioactive substances with a great potential for curbing the negative effects of stresses, acting on human skin cells on a day-today basis. In many cases these compounds appear to be less toxic, less allergenic, and, in general, more “biocompatible” than most of their synthetic counterparts. The same algal metabolites are recognized as promising ingredients for innovative cosmetics and cosmeceutical formulations. Ever increasing efforts are being put into the search for new natural biologically active substances from microalgae. This trend is also fueled by the growing demand for natural raw materials for foods, nutraceuticals, pharmaceuticals, and cosmetology, associated with the global transition to a “greener” lifestyle. Although a dramatic diversity of cosmeceuticals was discovered in macrophyte algae, single-celled algae are on the same level or even surpass them in this regard. At the same time, a large-scale biotechnological production of microalgal biomass, enriched with the cosmeceutical compounds, is more technically feasible and economically viable than that of macrophyte biomass. The autotrophic cultivation of microalgae is generally simpler and often cheaper than that of heterotrophic microorganisms. Cultivation in bioreactors makes it possible to obtain more standardized raw biomass, quality of which is less dependent on seasonal factors. Microalgae biotechnology opens many possibilities to the “green” cosmeceutical production. However, a significant part of microalgae chemoand biodiversity remains so far untapped. Consequently, bioprospecting and biochemical characterization of new algal species and strains, especially those isolated from habitats with harsh environmental conditions, is a major avenue for further research and development. Equally important is the development of approaches to cost-effective microalgae cultivation, as well as induction, extraction, and purification of cosmeceutical metabolites. World scientific community is rapidly accumulating extensive information on the chemistry and diverse effects of microalgae substances and metabolites; many substances of microalgal origin are extensively used in the cosmetic industry. However, the list of extracts and individual chemicals, isolated from them