Boron and maturity effects on biochemical parameters and antioxidant activity of pepper ( Capsicum annuum L.) cultivars

Pepper fruit (Capsicum annuum L.) is one of the best sources of carotenoids, carbohydrates, flavonoids, phenols, and antioxidant activity important in the human diet. The levels of bioactive compounds are variable and may be affected by cultivar, maturity stage, and boron concentration in the soil solution. A greenhouse experiment was conducted with the pepper cultivars Solario, Osho, Odysseo, and Arlequin treated with 5 boron concentrations (0.5, 1, 2.5, 5, and 10 mg B L -1 ) for 70 days. Fruits were sampled at 40 and 70 days and the concentration of carbohydrates, carotenoids, flavonoids, total phenols, and antioxidant activity (FRAP, DPPH) were measured. The experiment included 10 plants per B treatment and cultivar, with a total of 200 plants. The results obtained in this study showed that B toxicity reduced the level of carbohydrates in four commercial pepper cultivars grown in Greece and in other countries. The levels of carotenoids, flavonoids, and phenols were a function of pepper cultivar and boron treatment. Fruit maturation increased the level of carbohydrates, phenols, flavonoids, and antioxidant capacity. The cultivar Solario had the highest phenol concentration and also the highest FRAP value among the tested cultivars. In conclusion, boron toxicity decreased carbohydrate concentration and modified antioxidant activity in pepper fruit.