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.