Comparison of antioxidant contents of green and red leaf lettuce cultured in hydroponic systems under greenhouse, and conventional soil culture.

Abstract

Hydroponic technologies have increased the cultivated area under greenhouses covered with UV filter polyethylene film. However, there is a concern about the antioxidant contents of lettuces produced under these systems. In this study, it was compared to the antioxidant contents of green and red leaf lettuces produced in two hydroponic systems in a greenhouse, against the ones produced with the conventional cultivation system by Colombian farmers. The antioxidant analysis revealed significant statistical differences for DPPH and Anthocyanin analyses (P=0) versus all other culture systems. The best results were obtained in the conventional cultivation. Red lettuce obtained the highest value of FRAP (655.3±82.6 mgAAE 100g-1), ABTS (17.8±6.9 mmolTE 100g-1), total phenols (680.2±69.3 mgGAE 100g-1) and anthocyanin (126.2±6.9 mgC3G 100g-1). Green lettuce exhibited the most antioxidant activity of DPPH (20.7±5.6 mmolTE 100g-1). These results suggest a detrimental effect of the greenhouse covered with UV filter polyethylene film in the antioxidant production of lettuce. Finally, red leaf lettuce showed better antioxidant capacity independent of the cultivation system.