Natural products from extreme marine environments: Searching for potential industrial uses within extremophile plants

Extremophile plants, halophytes in particular, still remain largely unexplored and underutilized despite their high potential as source of industrial raw materials like natural antioxidants in industries related to pharmaceutical, cosmetics and functional ingredients. The goal of this study was to explore the phenolic content and the in vitro antioxidant and tyrosine inhibition properties of polyphenol-rich extracts of twenty-one extremophile plant species collected in saline habitats of the South of Portugal (Algarve). Aqueous acetone extracts of Lithrum salicaria, Cladium mariscus, Frankenia laevis, F. pulverulenta, Limoniastrum monopetalum, Aster tripolium and Typha domigensis had remarkable levels of total phenolics (≥230 mg GAE/g DW); Halopeplis amplexicaulis, Cladium mariscus, F. pulverulenta and Salsola vermiculata contained high levels of flavonoids (≥10 mg RE/g DW); tannins peaked in T. domingensis and C. mariscus (≥35 mg CE/g DW) and L. salicaria and A. tripolium had the upmost hydrocinamic acids content (≥60 mg CAE/g DW). Overall L. salicaria had the highest antioxidant activity and only P. lentiscus had the capacity to inhibit tyrosinase. As the most bioactive extracts were not cytotoxic towards mammalian cell lines, our results suggest that several halophytes present in Southern Portugal could be used in the food and/or cosmetic industries.