Adsorption/desorption characteristics and chromatographic purification of polyphenols from Vernonia patula (Dryand.) Merr. using macroporous adsorption resin

Abstract

Vernonia patula (Dryand.) Merr. has long been used as a traditional medicine in some parts of Asia and is a promising source of bioactive polyphenols. In this work, the adsorption/desorption characteristics and chromatographic purification of total polyphenols from V. patula (VPTP) by macroporous adsorption resin (MAR) were investigated. Static adsorption/desorption tests revealed that NKA-II resin was most suitable for purifying VPTP with the adsorption capacity of 92.54 ± 0.85 mg/g and desorption capacity of 71.03 ± 1.83 mg/g, that the Langmuir model afforded the best fit to the isotherm data, that the pseudo-second order model afforded the best fit to kinetics data, and that adsorption was a favourable, spontaneous, exothermic and physical reaction. Additionally, an efficient chromatographic purification process was developed. After purification by scale-up column chromatography (CC) on NKA-II resin under optimum conditions (for adsorption: 6 BV of aqueous solution of VPTP extract with an initial total polyphenols concentration of 3.84 mg/mL was loaded onto the column at 1.5 BV/h; for desorption: the column was eluted using 5.5 BV of 60 % EtOH at 3 BV/h), the content of VPTP improved 2.36-fold from 21.36 %–50.33 % with a satisfactory recovery of 83.45 %. Furthermore, high-performance liquid chromatography (HPLC) analysis showed that compared with the crude extract, the contents of chlorogenic acid and caffeic acid in VPTP-enriched extracts were obviously increased. The results indicated that this work provides a reliable basis for the industrial purification of VPTP using MAR.