Characterization of peroxidase-mediated chlorophyll bleaching in strawberry fruit

MARTÍNEZ GA; PEDRO MARCOS CIVELLO; CHAVES AR; AÑÓN MC

PHYTOCHEMISTRY

Pergamon Press

Lugar: United States; Año: 2001 vol. 58 p. 379 - 387

0031-9422

Peroxidase (POX) from strawberry fruits was analyzed for its capacity to bleach chlorophyll. The partially purified enzyme preperation catalyzed the bleaching of chlorophylls and their derivatives in the presence of H2O2 and phenolic compounds. The optimal reaction conditions were 35
C, pH 5.2 and ionic strength equal to 0.2. The maximum activity was observed at 1 mMof H2O2, while higher concentrations inhibited enzyme activity. Compounds with a high affinity to the heme group, radical scavengers and reducing agents, showed an inhibitory effect. Phenolic compounds such as umbelliferone, naringenin and p-substituted monophenols acted ascofactors. Instead, other phenolic compounds tested such as caffeic acid, catechin, ellagic acid, esculin and quercetin inhibited the activity of POX on chlorophylls. Phenolic compounds extracted from strawberry fruits showed an inhibitory effect on POX-chlorophyll bleaching activity, although this effect decreased markedly during ripening. POX showed higher affinity for compounds derivedfrom chlorophyll a than from chlorophyll b, and the enzyme preferentially degraded chlorophyll derivatives with the Mg2+ ion present and the phytol group removed. The POX-chlorophyll bleaching activity was found in all ripening stages from small green toripe, the highest activity corresponding to large green fruits. # 2001 Published by Elsevier Science Ltd. All rights reserved.Keywords: Fragaria x ananassa; Rosaceae; Strawberry; Chlorophyll; Peroxidase; Phenolic compounds