Optimized Extraction and Bioactivity Profiling of Phenolics from Bostrychia scorpioides (Hudson) Mont: A Sustainable Approach for Pharmaceuticals Applications.

This study presents a comprehensive approach to valorizing the red macroalga Bostrychia scorpioides (BS), collected from Oualidia lagoon, as a reservoir of compounds with biological activity. An extraction protocol combining ultrasound-assisted pretreatment with conventional maceration in 80% (v/v) hydroethanolic solvent was developed, and the recovery of phenolic compounds was maximized using response surface methodology (RSM) based on a Box-Behnken design (BBD). The model-predicted and experimentally validated optimal extraction conditions were 37.5 min of ultrasonication, an extraction temperature of 45 °C and 3.5 h of maceration, yielding a TPC of 341.45 µg GAE/g dw; the optimal extract was also rich in flavonoids and condensed tannins. In terms of bioactivity, the extract exhibited substantial antioxidant capacity, achieving 98.97% hydrogen peroxide scavenging, which strongly correlated with the phenolic concentration. Antibacterial evaluation revealed pronounced inhibition of Listeria monocytogenes, Staphylococcus aureus and Escherichia coli, with inhibition zones ranging from 9 to 19 mm and MIC values from 3.125 to 12.5 mg/mL. Crucially, cytotoxicity assessment on PBMCs demonstrated a favorable safety profile, maintaining over 85% cell viability at concentrations up to 200 µg/mL. High-Performance Liquid Chromatography (HPLC) and molecular docking simulations identified chlorogenic acid as a major bioactive constituent, displaying a high in silico binding affinity (- 8.0 kcal/mol) for aromatase, a validated target in oncological therapy. Taken together, these findings suggest that BS represents a sustainable and safe natural reservoir of antioxidant and antimicrobial compounds of interest for natural drug development.