Phenolic metabolites from Ceratonia siliqua L. pods: chemical characterization, soybean lipoxygenase-1 inhibition, and in vitro gallstone-dissolving capacity

Abstract

Introduction Carob (Ceratonia siliqua L., Fabaceae) is a Mediterranean tree whose pods are rich in phenolic metabolites and are credited with antioxidant, anti-inflammatory,hypolipidemic and antimicrobial properties. Methods The chemical composition of MECp was determined by high-performance liquid chromatography coupled with ultraviolet detection (HPLC/UV). Free radical-scavenging and ferric-reducing capacities were measured using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric-reducing antioxidant power (FRAP) analytical descriptors assays, and soybean LOX-1 inhibition was assessed in vitro and examined in silico by molecular docking against the enzyme (PDB ID: 3O8Y). Gallstones removed at surgery were confirmed as cholesterol stones by Fourier transform infrared spectroscopy with attenuated total reflectance (FTIR-ATR) and then incubated in MECp under continuous agitation for 4 weeks, with a sodium chloride solution (NaCl, 9 g/L) as control. Gallstone mass after drying at 40 °C, the percentage of gallstone-dissolving capacity (% GDC) and the pH of the medium were recorded weekly. Results HPLC/UV analysis identified 20 phenolic metabolites in MECp. The extract contained 160.68 mg GAE/g DE of total phenolics and 9.19 mg QE/g DE of total flavonoids, with median inhibitory concentrations (IC50) of 0.16, 0.86 and 0.19 mg/mL for the DPPH, FRAP and soybean LOX-1 inhibition assays, respectively. Compared with the control, MECp produced a highly significant increase in % GDC over time, and the docking analysis revealed strong and stable interactions between the major polyphenols and the soybean LOX-1 active site. Discussion The dissolution obtained with MECp is consistent with its phenolic composition, and the docking results agree with the soybean LOX-1 inhibition measured in vitro. These findings identify MECp as a promising natural candidate for cholesterol gallstone management and support further preclinical investigation.