Eco-Friendly Extraction and Valorization of Cucumis metuliferus E. Mey. ex Naud. Peel and Pulp: Optimization of Phenolic Recovery and Evaluation of Biological Activities.

This study focused on optimizing the ultrasound-assisted extraction process for both the peel and pulp of Cucumis metuliferus E. Mey. ex Naud. grown in Tunisia, using response surface methodology. The optimization targeted total phenolics content, total flavonoids content, as well as antioxidant activities evaluated by ferric reducing antioxidant power and 1, 1-diphenyl-2-picrylhydrazyl assays. A central composite design was employed to investigate the influence of three key parameters: extraction time, extraction temperature, and liquid-to-solid ratio. The ultrasound-assisted extraction (UAE) parameters were set as follows: extraction time ranging from 6.59 to 23 min, ultrasound temperature from 33.18°C to 66.81°C, and liquid-to-solid ratio from 13.18 to 46.81 mL/g. The optimal parameters for pulp extraction were determined to be a 15.76-min extraction time, a temperature of 50.50°C, and a solvent-to-solid ratio of 30.54 mL/g. High-performance liquid chromatography quantification identified gallic, chlorogenic, and caffeic acids as the main phenolic compounds, and the corresponding extracts exhibited potent, dose-dependent anti-inflammatory and antimicrobial effects. This study highlights a sustainable and eco-friendly process that supports the circular economy and offers a promising approach for the industrial production of antioxidant-rich Cucumis metuliferus extracts.