Antioxidant activity, enzyme inhibition, photoprotection, cytotoxicity, and phytochemical profiling of sea lavender (Limonium algarvense Erben) seed extracts for dermo-cosmetic use

Background: Despite sea lavender being a medicinal species, research on its seeds’ biological properties and chemical composition is unexplored. Thus, this study evaluated the effect of different extraction solvents on the biological activities and chemical profile of greenhouse-cultivated sea lavender seeds, aiming at their potential use as a dermo-cosmetic ingredient. Therefore, ethyl acetate, acetone, ethanol, and water extracts were examined for their antioxidant activity, enzyme inhibition, photoprotection, and cytotoxicity, followed by phytochemical analysis through spectrophotometric methods, further detailed by Ultrahigh-Performance Liquid Chromatography Coupled with Electrospray Ionization Mass/Mass Spectrometry (UHPLC-Esi-MS/MS). Results: The water extract demonstrated significant antioxidant activity, evidenced by low half maximal effective concentration (EC50) values in scavenging 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radicals, reducing iron and chelating copper (296, 478, 230 and 678 µg/mL, respectively). The ethanol extract was more effective in inhibiting cosmetic-related enzymes, particularly elastase and hyaluronidase (2.18 and 3.21 µg/mL, respectively). The water and acetone extracts had the highest sun protection factors (23.2 and 18.9, respectively). All the extracts had nil to weak cytotoxicity (70–120% cell viability) towards mammalian cell lines. The water extract had the highest phenolics and condensed tannins (115 and 78.30 mg/g extract, respectively), while the ethanol contained the most flavonoids (62.73 mg/g extract). UHPLC-ESI–MS/MS analysis identified ethyl gallate, myricetin, rutin, and quercetin as major components of the ethanol extract, whereas myricetin-O-rutinoside isomers are predominant in the water extract. Conclusions: These findings highlight the potential of greenhouse-cultivated sea lavender seeds as potential dermo-cosmetic ingredients, with ethanol and water extracts demonstrating superior biological activities and chemical profiles, significantly contributing to general skin health and protection.