Phytochemical screening, physicochemical profiling, and bioactivity assessment of Ceratonia siliqua seed aqueous extract. Antioxidant and antimicrobial properties

The growing interest in plant-derived bioactive compounds has intensified the search for novel antioxidants and antimicrobials. This study investigates the phytochemical profile, antioxidant potential, and antibacterial efficacy of the aqueous extract of Ceratonia siliqua seeds (AECS), employing a multi-technique analytical approach for the first time. AECS was analyzed for total phenolic (TPC), flavonoid (TFC), and condensed tannin content. Key compounds were identified using HPLC–ESI–MS/MS, while FTIR and XRD characterized functional groups and crystalline structures. SEM–EDX provided morphological and elemental insights. Antioxidant activity was assessed via DPPH, ABTS, and FRAP assays, and antibacterial effects were evaluated against Gram-negative and Gram-positive bacteria using MIC and MBC tests. AECS exhibited high phenolic and flavonoid content, with HPLC–MS/MS confirming the presence of gallic acid, catechin, and quercetin. FTIR and XRD provided structural insights, while SEM–EDX revealed a porous morphology with bioactive elements. Phytochemical screening showed a total phenolic content of 30.14 ± 0.16 mg GAE/g DM, a flavonoid content of 8.60 ± 0.80 mg CAE/g DM, and a condensed tannin content of 1.49 ± 0.08 mg CAE/g DM. AECS demonstrated strong antioxidant activity (DPPH IC₅₀ = 0.02 ± 0.06 mg/mL; FRAP IC₅₀ = 6.54 ± 0.01 mg/mL) and exhibited potent antibacterial effects against all four bacterial strains, with the strongest activity observed against E. faecium (MIC = 0.78 ± 0.00 μg/mL). While AECS shows activity against multiple bacterial strains, its mechanism of action appears to be predominantly bacteriostatic, rather than bactericidal. This study provides the first comprehensive chemical characterization of AECS using combined spectroscopic and microscopic techniques, unveiling its structural and bioactive properties. These findings position C. siliqua seed extract as a promising natural antioxidant and antimicrobial agent for pharmaceutical and nutraceutical applications.