TOWARDS THE CHARACTERIZATION OF RADICALS FORMED IN RHIZOMES OF IRIS-GERMANICA

When Iris germanica, Hydrocotyle verticillata, Glyceria maxima and Jun cus effusus plants were treated anoxically and subsequently returned t o air, long-lived free radicals were rapidly generated in the plant ti ssues and were detected by EPR spectroscopy. The free radicals in I. g ermanica rhizomes were extracted into aqueous alkali; the EPR spectrum of the aqueous solution showed fine structure which indicated the pre sence of at least two oxygen-centred radicals. The EPR data, and the r adical lifetimes, suggested that they were probably semiquinone radica l anions. Product analysis of the alkaline extract indicated that the main components were a set of flavonoids including quercetin, irisolon e, 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-d ihydroxy- 1,4-dihydroxy- or trihydroxy-substitution patterns, by inter action with superoxide. However, the EPR-detected radicals were probab ly derived from flavonoids more heavily substituted than quercetin.