Oxidative Stress and Antioxidative System in Ripening Ber (Ziziphus mauritiana Lam.) Fruits

The present investigations were undertaken to ascertain the extent of lipid peroxidation, oxidative stress and antioxidative system during ripening of two varieties of ber fruits (Ziziphus mauritiana Lam.) differing in their shelf lives, viz. Umran (8–9 days) and Kaithali (4–5 days). Based on visual observations, fruits were categorized as immature green (IG), mature green (MG), turning colour (TC), ripe (R) and overripe (OR). Lipoxygenase (LOX) activity, malondialdehyde (MDA) value and H2O2 content increased significantly during ripening in both varieties, obtaining 3-, 3and 2.5-fold increase in Umran and 4-, 3.5and 3-fold increase in Kaithali, respectively. Kaithali being short-lived variety, exhibited higher values of these parameters at almost all the stages of fruit ripening. Activity of superoxide dismutase (SOD), glutathione reductase (GR) and ascorbate peroxidase (APX) increased during initial stages but thereafter decreased, whereas that of peroxidase (POX) decreased continuously during ripening. On the other hand, catalase (CAT) activity increased continuously as ripening progressed. In general, antioxidative enzymes exhibited comparatively higher activity in Umran. Total ascorbic acid content increased from IG to TC stage, while total glutathione increased up to MG stage and thereafter decreased in both varieties. Kaithali had higher content of ascorbate than Umran. b-Carotene and a-tocopherol also decreased as ripening progressed. However, the decrease was more pronounced in Umran as compared to Kaithali.