Comparison of Extraction of Phytochemicals and Bioactive Compounds from Licorice ( Glycyrrhiza glabra L. ) by Conventional and Green Techniques: A Systematic Review

Licorice (Glycyrrhiza glabra L.) is a rich source of phytochemicals and bioactive compounds (BCs), and growing interest in plant-derived BCs has increased attention toward efficient extraction strategies. Extraction methodology plays a critical role in determining yield, efficiency, and sustainability. This systematic review evaluates the effectiveness of conventional and green extraction techniques for isolating BCs from licorice. A total of 42 eligible studies were identified from multiple databases, focusing on extraction, analysis, and identification of licorice BCs. Conventional methods, including Soxhlet and maceration, generally yielded 24.32-37.63 mg/g of glycyrrhizic acid, requiring prolonged extraction times (5-12 h) and large solvent volumes. In contrast, green extraction techniques significantly enhanced extraction efficiency within shorter durations (3-120 min). Glycyrrhizic acid yields ranged from 28.06-217.7 mg/g for ultrasound-assisted extraction, 22.6-45 mg/g for microwave-assisted extraction, 18.5-19.5 mg/g for subcritical water extraction, 340-544 mg/g for supercritical CO₂ extraction, 20.99 mg/g for pressurized liquid extraction, and 43.78 mg/g for infrared-assisted extraction. These variations highlight the influence of operational parameters such as temperature, time, solvent characteristics, and solid-liquid ratio. Overall, green extraction methods offer superior performance and environmental advantages, representing promising alternatives for sustainable and large-scale recovery of licorice BCs.