Degradation of chlorophylls in strawberry fruits: ‘in vitro’ evidence of peroxidase-mediated bleaching

MARTÍNEZ GA; CIVELLO, PM; CHAVES AR; AÑÓN MC

ACTA HORTICULTURAE

International Society for Horticultural Science

Año: 2001 vol. 553 p. 551 - 553

0567-7572

Peroxidase (POX) from strawberry fruits was analyzed regarding its capacity to bleach chlorophyll; it catalyzed the bleaching of chlorophylls (Chls) and their derivatives in the presence of H2O2 and phenolic compounds. The optimum reaction conditions were 35°C, pH 5.2, ionic strength 0.2, and 1 mM H2O2. Compounds with high affinity for the heme group, radical scavengers and reducing agents inhibited the reaction. Phenolics acted as cofactors, and monophenols with a p-position substitution showed the highest activities. Natural coumarins, flavonoids and some of their derivatives were also evaluated. Only umbelliferone and naringenin were effective as cofactors. Some of the tested phenols proved not only non-effective but were also inhibitory. Endogenous phenols of strawberries showed an inhibited POX-chlorophyll bleaching although this inhibition decreased markedly during ripening. POX showed higher affinity for a derivatives than for b derivatives. Moreover, POX more easily degraded derivatives with the Mg2+ ion located in the ring and with the phytol group removed. The chlorophyll bleaching activity of POX was present at all the ripening stages analyzed. It was detected in small green fruits, increased in large green fruits and decreased during ripening.