An Integrated Process for Preparing High-Purity Quercetin from Sophora japonica Buds through Acid Hydrolysis and pH-Controlled Purification

This invention presents an efficient, scalable process for producing highpurity quercetin through acid hydrolysis, hot filtration, mother-liquor recycling, and sodium-borate-assisted pH-controlled fractional precipitation. Replacing column chromatography, the process achieved 99.8% purity. IR, MS, and NMR confirmed product identity, while individual impurities remained below 0.1%, meeting evaluated USP 44 quality requirements.