Radical scavenging characteristics of condensed tannins from barks of various tree species compared with quebracho wood tannin

Abstract

The object of this study was to elucidate the relationship between the chemical structure of purified condensed tannin polymers from tree species and their radical scavenging characteristics. By means of ¹³C-NMR spectrometry and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS), four kinds of proanthocyanidins were identified: prorobinetinidins, profisetinidins, procyanidins, and prodelphinidins. The tannins were submitted to radical scavenging assays with DPPH and galvinoxyl radicals and from the time-course of the reactions was concluded: 1) Tannins with pyrogallol type B-ring scavenge radicals in the beginning faster than those with catechol type B-ring. 2) Tannins with catechol type B-ring needs more time to scavenge the same amount of radicals as those with pyrogallol type B-ring. 3) The IC₅₀ values of tannins with catechol type B-ring decrease after longer reaction times with the galvinoxyl radical. 4) Radical scavenging with DPPH radical proceeds faster than that for the galvinoxyl radical.