Targeted Isolation of Glycyrrhizic Acid from the Phloem of Glycyrrhiza glabra via Macroporous Resin

Glycyrrhizic acid (GA), the primary bioactive triterpenoid saponin in Glycyrrhiza glabra (licorice), is widely utilized in pharmaceutical formulations. Conventional extraction methods utilizing whole licorice slices is often inefficient due to complex matrix interference from the xylem and periderm. Initial analysis revealed that the distribution of GA is uneven, with phloem tissue serving as the primary storage site (accounting for 56.82 % of the total content) compared to xylem and periderm. Consequently, phloem-specific extraction was adopted to minimize matrix interference. By selectively using phloem tissue as the feedstock, we minimized the initial load of lignin and pigments. Subsequently, five macroporous adsorption resins were screened for purification, with HPD-400 exhibiting superior adsorption capacity (37.35 mg/g at 25°C) and adsorption kinetics. Optimization experiments indicated that adsorption was maximized at pH 2.0, driven by hydrophobic interactions with the undissociated GA molecules. Furthermore, a stability-preserving gradient elution protocol using neutral ethanol (30 % wash/70 % accumulate) was developed to avoid the hydrolysis and isomerization risks associated with alkaline modifiers. Under these optimized conditions, the phloem-derived GA was purified to 82.53 %±2.64 %. This study demonstrates that targeted phloem extraction combined with resin chromatography offers a streamlined for producing high-purity GA.