Nonthermal high-pressure microalgae extracts: A new source of natural ingredients for cosmetics

Microalgae are one of the most prominent sources of ingredients for the cosmetic industry not only due to their diversity but, importantly, due to the low environmental impact in production and extraction. A sustainable extraction process requires the use of effective and environmentally friendly solvents that guarantee an extract with a relevant content and in high yields. In this work, Chlorella vulgaris, Nannochloropsis oceanica, Tetraselmis chui, Chlorococcum amblystomatis and Phaeodactylum tricornutum microalgae species grown in tubular photobioreactors were used to validate a high-pressure extraction (HPE) method. Extraction yields up to 57 % were obtained depending on the used solvent (water, ethanol, or acetone). The extracts were then characterized regarding their phytochemical composition (total phenolic, protein, chlorophylls content, and chlorophyll a). Aqueous extracts showed high protein content (6–51 μg/mg biomass), while ethanolic and acetone extracts showed high amounts of phenolic compounds (0.0007–0.03 μg/mg biomass). The levels of photosynthetic pigments (0.1–11 μg/mg biomass) associated with antioxidant and anti-inflammatory properties were higher when extracted using ethanol and high-pressures. Chlorella vulgaris aqueous extracts presented higher protein content while Nannochloropsis oceanica and Tetraselmis chui ethanolic extracts presented higher amounts of photosynthetic pigments. The effect of the extracts over the metabolic activity of primary human dermal fibroblasts, keratinocytes, melanocytes, and adipocytes was dependent on both microalgae species and cell type. In adipocytes and fibroblasts, extracts presented an IC50 > 500 μg/mL, except for the one of Phaeodactylum tricornutum in fibroblasts (IC50 < 150 μg/mL). In contrast, the IC50 was below 500 μg/mL for most of the extracts in keratinocytes and melanocytes. Overall, extracts of sustainably-grown microalgae obtained by a high-pressure method are a promising source of natural ingredients for cosmeceutical applications.