Chemical Characterization and Biological Activity of Astaxanthin Extracted from Callinectes sapidus By-Products: Implications for Oxidative Stress and Inflammatory Skin Disorders

: Astaxanthin (AST) is a carotenoid with powerful antioxidant and anti-inflammatory properties and increasing interest in dermatological and nutraceutical applications. In this study, AST-rich extracts were obtained from by-products of the blue crab Callinectes sapidus and chemically characterized using HPLC-DAD analysis. The antioxidant activity of the extracts was assessed through complementary spectrophotometric assays (DPPH and FRAP). Comparable AST contents were detected in the two extracts, with values of 1.269 ± 0.006 and 1.219 ± 0.015 mg/100 g dry weight for EtOH and IPrOH, respectively. However, the EtOH extract exhibited higher antioxidant activity, reaching 0.10 ± 0.01 mg Trolox equivalents (TE)/g in the DPPH assay and 0.27 ± 0.02 mg TE/g in the FRAP assay, compared with 0.08 ± 0.01 and 0.11 ± 0.03 mg TE/g for the IPrOH extract. The biological activity of AST extracts was further evaluated against the opportunistic pathogen Staphylococcus aureus and beneficial lactic acid bacteria. AST exhibited moderate antibacterial activity against S. aureus, with an MIC value of 50 μg/mL and inhibition zones up to 14 mm at 200 μg/disc, while promoting the proliferation of Lactobacillus plantarum, Lactobacillus casei, and Lactobacillus reuteri. These findings highlight the prospective valorization of blue crab by-products as a sustainable supply of antioxidant and microbiota-modulating compounds with possible applications in skin health and cosmetic formulations.