Elucidating deep eutectic solvent-mediated recovery of phenolic compounds from cubeb pepper (piper cubeba l.f.) and their antioxidant potential

Objective: Conventional extraction methods for phenolic recovery often rely on large amounts of organic solvents and may exhibit limited efficiency. This study aimed to develop and optimize a sustainable deep eutectic solvent (DES)-assisted automatic solvent extraction (ASE) process for the recovery of phenolic compounds from Piper cubeba L.f. fruits. Methods: Prepared DES systems were characterized by Fourier-transform infrared (FTIR) spectroscopy to confirm DES formation and investigate intermolecular hydrogen-bond interactions between their constituent components. Different DES systems were screened and compared using principal component analysis (PCA) to identify the most effective extraction medium. The selected DES system, lactic acid:ethylene glycol (2:1), was subsequently optimized using response surface methodology (RSM) based on a Box–Behnken design. Immersion time, water addition, and sample mass were evaluated as the main extraction variables. Results: The extraction parameters significantly influenced total phenolic content (TPC), antioxidant activity, and 2-hydroxycinnamic acid recovery. TPC values ranged from 25.55 to 71.54 mg-GAE/g-DM. Antioxidant activity varied between 17.41 and 32.90 mg-TEAC/g-DM for the DPPH assay and between 8.93 and 32.51 mg-TEAC/g-DM for the ABTS assay. The content of 2-hydroxycinnamic acid ranged from 5.95 to 26.12 mg/g-DM. Optimum extraction conditions were determined as 24.95 min immersion time, 52.55% water addition, and 0.70 g sample mass, with prediction errors below 2%. Conclusion: DES-assisted ASE enabled efficient phenolic recovery and accurate process optimization, demonstrating its potential as a sustainable alternative to conventional solvent-based extraction methods. The findings highlight the suitability of the lactic acid:ethylene glycol (2:1) DES system for enhancing the extraction of bioactive compounds from P. cubeba fruits and support its potential application in food, nutraceutical, pharmaceutical, and cosmetic formulations.