Abstract:

In the present study, we used macroporous resin adsorption to purify total flavonoids from the crude extract of Zanthoxylum bungeanum leaves and tested the reducing power and DPPH free radical scavenging activity of the final purified product. Eight macroporous resins were measured for their adsorption/desorption capacity towards total flavonoids from Zanthoxylum bungeanum leaves, and D4020 was the selected resin considering the highest adsorption capacity and higher desorption ratio. The optimum conditions for D4020 resin adsorption/desroption were as follows: sample (at pH 5, saturated with NaCl) concentration 2.19 mg/mL, sample flow rate 2 BV/h, desorption flow rate 2 BV/h and amount of 70% ethanol used as desorption solvent 2 BV. The optimized purification resulted in an increase in the purity of the total flavonoid extract of Zanthoxylum bungeanum leaves from 3.18% to 16.92%. In the presence of NaCl, the adsorption equilibrium ould be fitted by Freundlich isotherm equation. Moreover, the adsorption capacity increased with increasing NaCl amount. The IC50 of the final purified product for scavenging DPPH free radicals was 1.8 μg/mL, much lower than 4 μg/mL of VC, indicating better DPPH free radical scavenging activity; the final purified product also presented significantly higher reducing power than VC. Thus, Zanthoxylum bungeanum leaves deserve to be exploited as a plant resource containing flavonoid compounds.

Key words: Zanthoxylum bungeanum leaves, total flavonoids, macroporous resin purification, adsorption characteristics, antioxidation