Activity-guided screening of the antioxidants from Paulownia tomentosa var. tomentosa Bark

Abstract

Tree barks, as a type of forestry residues, are a rich and renewable bioresource that can produce high value-added products. Paulownia tomentosa var. tomentosa (PTT) has been extensively used in traditional Chinese medicine to cure various diseases. However, the antioxidative activity of the chemical constituents of the tree has not yet been investigated. In this study, the bark of PTT were extracted and fractioned. Then the resulting ethyl acetate (EtOAc) soluble fraction, which exhibited the strongest antioxidative effect, was subjected to repeated open column chromatography for purification. The screening process was carried out under the guidance antioxidative activity via diphenylpicrylhydrazyl (DPPH) radical scavenging assay. Eight phenolic compounds, glucodistylin (I), luteolin (II), ellagic acid (III), cistanoside F (IV), campneoside II (V), isocampneoside II (VI), verbascoside (VII), and isoverbascoside (VIII), were isolated and their structures were elucidated by various spectroscopic analyses. Among the phenolics, II~VIII showed significant antioxidative activity.

Keywords

• Isolation and purification
• Structure elucidation
• Total phenolic contents
• Paulownia tomentosa var. tomentosa
• Antioxidative activity
• Activity-guided screening