Enhancing Allicin Purity and Gastrointestinal Bioactivity Profile of Garlic Extracts Through Optimized Supercritical-CO2 Extraction and Molecular Distillation Processes

Allicin, the most critical bioactive compound of garlic (Allium sativum L.), is of significant industrial importance when extracted at high purity while preserving its structural integrity. In this study, the combined use of supercritical-CO₂ (SC-CO₂) extraction and molecular distillation (MD) techniques was investigated to obtain garlic extracts with high allicin content from Gaziantep (Araban) garlic. The SC-CO₂ extraction process was optimized using Response Surface Methodology (RSM) within a range of 150-300 bar pressure, 50-80% co-solvent concentration and 0.5-3.0 mL/min solvent flow rate. The obtained extracts were characterized by LC-ESI-DAD-MS/MS, and their biological activities were evaluated using a comprehensive in vitro digestion model. Allicin in vitro digestion was performed using models simulating gastrointestinal conditions of young adults (<65 years) and older adults (>65 years), and its bioactive properties were comparatively evaluated. In the antimicrobial analysis, for SC-CO₂, a strong activity was demonstrated against Staphylococcus aureus and Escherichia coli in the oral phase of the in vitro digestion model, with inhibition zones of 36.33 mm and 26.50 mm in young samples and 34.67 mm and 25.83 mm in older samples, respectively. Owing to the immediate nucleophilic attack triggered by the subsequent alkaline pH shift and pancreatic enzymatic stress, free allicin underwent total structural degradation, falling below detectable limits within the intestinal chyme. In terms of purification performance, allicin content increased from 45.77% after SC-CO₂ extraction to 67.10% after molecular distillation. Crucially, due to the immediate nucleophilic attack driven by the subsequent alkaline pH shift and pancreatic enzymatic stress, free allicin underwent complete structural degradation and was rendered strictly undetectable within the intestinal chyme. This approach provides a sustainable and environmentally friendly purification strategy that effectively limits the thermal degradation of allicin. The results present a practical framework for the scalable production of allicin-rich nutraceutical intermediates and functional food ingredients.