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

Abstract

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 CO(2) 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. Selection of an optimal extraction method for bioactive compounds from licorice has gained significant importance.Traditional methods for extracting bioactive compounds from licorice have typically involved techniques such as Soxhlet extraction, batch extraction, heat-reflux extraction, and maceration.Novel eco-friendly extraction methods for licorice bioactive compounds include microwave-assisted, ultrasound-assisted, enzyme-assisted, and infrared-assisted extraction, as well as subcritical water extraction, supercritical carbon dioxide extraction, and pressurized liquid extraction.Compared to traditional methods, the innovative extraction techniques not only enhance efficiency and yields but also provide several benefits, including minimized impurities, reduced solvent requirements, and lower energy consumption.