Phytochemical profiling and assessment of antioxidant and antibacterial activities of the green macroalga Caulerpa prolifera from the Antalya coast

Macroalgae are increasingly supported for utilization and development in pharmacology, food, and biotechnology due to their high bioactive potential. This study aimed to characterize the phytochemical profile of C. prolifera extracts and to evaluate their in vitro antioxidant and antibacterial activities. The extracts exhibited total phenolic (TPC) and total flavonoid contents (TFC) values of 2.68±0.22 and 18.94±0.68 µg GAEs/mg, while flavonoid contents were determined as 51.05 and 7.26±0.09 µg QEs/mg. HPLC-DAD analysis identified major metabolites including chlorogenic acid, 4-hydroxybenzoic acid, t-ferulic acid, hydroxycinnamic acid, naringin, o-coumaric acid, rosmarinic acid, salicylic acid, quercetin, t-cinnamic acid, rutin, and naringenin. Antibacterial evaluation demonstrated variable susceptibility among Gram-negative and Gram-positive strains, with MIC values ranging from 7.5 to 5.25 mg/mL. While the ethanol extract exhibited the strongest antioxidant activity in the ABTS•⁺ (IC50: 333.16±0.74 µg/mL) and CUPRAC (A0.50: 538.5±0.02) assays, all extracts showed limited DPPH scavenging capacity (IC50:>800 µg/mL). The ethanolic extract also demonstrated the highest metal chelating capacity (IC50: 327.15±0.63 µg/mL). In conclusion, this study demonstrates that ethanol is the most effective solvent for recovering antioxidant bioactive components from C. prolifera and recommends its use in extraction-based studies.