Preparative purification of polyphenols from sweet potato (Ipomoea batatas L.) leaves by AB-8 macroporous resins

In this study, the adsorption properties of AB-8 macroporous resin for sweet potato leaf polyphenols was investigated. The adsorption mechanism was elaborated by the Langmuir and Freundlich equations, and the purification parameters were optimised by adsorption and desorption tests. The constituents and their contents of the purified products were analysed, and the antioxidant activities were determined. The results showed that the optimal processing parameters were as follows: an initial polyphenol concentration of 2.0 mg chlorogenic acid equivalent (CAE)/ml, pH 3.0, an ethanol desorption solution concentration of 70% (v/v) and a flow rate for feeding and elution of 1 BV/h. The purified products mainly contained eight phenolic constituents and the contents of three di-caffeoylquinic acids were relatively higher than the other constituents. The purified products possessed strong antioxidant activities. In conclusion, purification by AB-8 macroporous resin was highly efficient, economic and environmentally friendly and has a great industrial production potential.