Optimization of ultrasound-assisted extraction of bioactive compounds from carob pulp using response surface methodology

Carob plant extracts contain a variety of secondary metabolites (SM) with potential health benefits. Factors such as the extraction method and the geographical origin of the plant influence the extraction yield and quality of SM extracts. This study aims to increase the percentage of aqueous fraction in the solvent used to extract SM from carob pulp from distinct regions of Morocco (Ghafsai and Tainest). At the same time, it seeks to maximize the total phenolic content (TPC) in the extracts, minimize degradation, and preserve their integrity. A preliminary screening was conducted to assess the extraction efficiency of pure aqueous and organic solvents, revealing that water, methanol, and ethanol were the most effective solvents. The mixture response surface design methodology was then applied to investigate the synergistic effect of these solvents on the extraction of Total Phenolic Content (TPC). The results from the mixture design methodology (MDM) demonstrated that the optimal solvent system was a water/methanol/ethanol blend (50:30:20 v/v/v), yielding TPC concentrations of up to 55.47 +/- 0.01 and 41.85 +/- 0.04 mg GAE/g from carob samples collected in Ghafsai and Tainest, respectively. These extracts also exhibited notable IC50 values (DPPH: 328.18 +/- 0.21 and 879.06 +/- 0.15, ABTS: 65.71 +/- 0.2 and 128.05 +/- 0.17, FRAP: 328.18 +/- 0.21 and 879.06 +/- 0.15 mu g/mL for Tainest and Ghafsai samples, respectively). This study underscores the synergistic effect of the solvent mixture on TPC extraction and the influence of interregional variation on SM contents. Overall, this study advocates for the promotion and increased utilization of water as a green solvent in SM extraction from plant material, aiming to mitigate toxicity and risks associated with high proportions of organic solvents used in the extraction process.