Purification of phenolics from Plantago depressa by macroporous resin: Adsorption/desorption characteristics, chromatographic process development and UPLC-TQ-MS/MS quantitative analysis

Plantago depressa is a well-known edible and medicinal plant, characterized by its high health-promoting properties and nutritional value, and therefore possesses substantial untapped development potential. This study aimed to purify phenolic compounds from P. depressa using macroporous resins. Among the eight resins tested, NKA-II resin emerged as the most effective for the purification of total phenolics from P. depressa (PDTP). Adsorption characteristics were investigated, revealing that the pseudo-second-order kinetic model and Langmuir isotherm model best described the adsorption. The adsorption process was determined to be spontaneous and exothermic, characterized predominantly by physisorption mechanisms. Subsequently, the chromatographic process was optimized for the efficient purification of PDTP. After purification, the purity of PDTP increased from 18.72 ± 1.06% to 71.85 ± 1.43%, and the contents of six main phenolics (chlorogenic acid, 4-hydroxybenzoic acid, caffeic acid, plantamajoside, verbascoside, and luteolin 7-O-glucoside) were quantified simultaneously by UPLC-TQ-MS/MS and increased by 2.5- to 5.0-fold. Moreover, the purification process significantly enhanced the antioxidant and antiproliferative activities of the PDTP extracts. Therefore, the chromatographic method utilizing NKA-II resin shows promising potential for the purification of PDTP, offering valuable applications within the food and pharmaceutical sectors.