Total phenolic content and peroxidase activity in Salanova lettuce

Abstract

Lettuce (Lactuca sativa L.) belongs to a group of leafy vegetables commonly used as a salad in human nutrition. As minimally processed food product, it is an important source of vitamins, minerals and various antioxidative compounds. In our greenhouse experiment, two Salanova let tuce cultivars (‘Aquino‘ RZ- green and ‘Gaugin‘ RZ- red multi-leaf butterhead) were grown in the fertile soil during three successive seasons (autumn, winter and spring). The aim of the study was to examine the effect of different microbiological fertilizers (EM Aktiv, Vital Tricho and combination of EM Aktiv and Vital Tricho), cultivars and growing seasons on the total phenolic content and peroxidase activity. Our results showed that in all seasons red cultivar ‘Gaugin‘ had higher total phenolic content compared to green cultivar ‘Aquino‘. Their highest level was measured in au tumn with fertilizer Vital Tricho (549.14 µg GAE g-1 FW). The elevated phenolic status of red versus green cultivar was further strengthened by its higher level of peroxidase with the highest activity measured in spring with combination of fertilizers EM Aktiv and Vital Tricho (0.43 U mg-1 prot). The higher peroxidase activity and content of UV-absorbing phenolics, as plant-borne substrates of these enzymes, in the red cultivars indicate that the red leaves are better equipped to combat oxidative stress. Consequently, red cultivar ‘Gaugin‘, with increased synthesis of health-promoting antioxidants, could be considered as functional food in human diet.