Catechin as a radical scavenger in paraquat-treated Prunus avium

Young shoot discs of sweet cherry (Prunus avium L.) were sampled at various dates from elongating internodes of vigorous shoots and incubated for 4 days in 0.04 mM paraquat (1,1-dimethyl-4,4-bipyridinium dichlorid). The histochemical response was a massive deposition of flavanols along the outer margin of cells of pith, phloem and cortex. Even the outer cambium layer responded in this way. Flavanol inclusions in the cortex disappeared upon addition of paraquat. The paraquat effects described were reversed by addition of 0.16 mM (+)-catechin to paraquat in the incubation medium. Similar treatments were performed with small discs of mature leaves indicating a massive displacement of the cytoplasm by paraquat which again was overcome by (+)-catechin. Epicatechin, (+)-catechin as well as five proanthocyanidins could be identified by HPLC-CRD techniques from leaves and phloem of cherry. The possible functions of (+)-catechins and their oligomeric forms in preserving the normal cellular organization were discussed.