Towards the characterization of radicals formed in rhizomes of Iris germanica

Robert M.M. Crawford*, David A. Lindsay, John C. Walton, Brigitte Wollenweber-Ratzer

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)


When Iris germanica, Hydrocotyle verticillata, Glyceria maxima and Juncus effusus plants were treated anoxically and subsequently returned to air, long-lived free radicals were rapidly generated in the plant tissues and were detected by EPR spectroscopy. The free radicals in I. germanica rhizomes were extracted into aqueous alkali; the EPR spectrum of the aqueous solution showed fine structure which indicated the presence of at least two oxygen-centred radicals. The EPR data, and the radical lifetimes, suggested that they were probably semiquinone radical anions. Product analysis of the alkaline extract indicated that the main components were a set of flavonoids including quercetin, irisolone, selenone and derivatives of irigenin. The main flavonoids had more reduced and/or more alkylated structures than those from I. germanica grown under normal aerobic conditions. Semiquinone radical anions can readily be generated from quercetin, and similar flavonoids with 1,2-dihydroxy-, 1,4-dihydroxy- or trihydroxy-substitution patterns, by interaction with superoxide. However, the EPR-detected radicals were probably derived from flavonoids more heavily substituted than quercetin.

Original languageEnglish
Pages (from-to)979-985
Number of pages7
Issue number4
Publication statusPublished - 7 Nov 1994


  • electron paramagnetic resonance
  • flavonoids
  • free radicals
  • Glyceria maxima
  • Hydrocotyle verticillata
  • Iris germanica
  • Juncus effusus
  • Mentha aquatica
  • superoxide.


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