Effect of different soil fertilization treatments on phytochemicals, a case study: antioxidant polyphenols from Lactuca sativa (var. Maravilla de Verano) extract

Reactive oxygen species (ROS) and oxidative stress are always more recognized to play a central role in the etiology of cell dysfunction and tissue damage. In oxidative stress conditions, the balance between the radical formation and protection, which is normally present in the cells, is altered. This leads to the oxidative damage of all the biological molecules present in our body, such as nucleic acids, proteins, lipids, and the initiation for aggravation of diverse pathological states. Finding natural antioxidants from plant materials as alternatives to synthetic ones is a field of growing interest. Actually, antioxidants are substances that neutralize both free radicals and their negative effects. They act at different stages (prevention, interception, and repair), using various mechanisms as reducing agents by donating hydrogen, quenching singlet oxygen, acting as chelators, and trapping free radicals. Among vegetables, green lettuce (Lactuca sativa L.) is of primary importance, as it is consumed worldwide as a fresh produce. The absence of any cooking process emphasizes the importance of this produce, as it preserves the degradation of the thermolabile chemical species having potential nutraceutical interest. It is known that polyphenols have anticancer and anti-inflammatory properties, as well as the ability of reducing oxidative stress. The present study aims to investigate the anti-oxidant activity on macrophages of the polyphenolic extracts of green lettuce cultivated under different fertilization treatments. Our results indicate that Lactuca sativa extract reducesoxidative stress markers, as ROS release and nitrotyrosine formation, and triggers antioxidant cellular response, as Nrf2 activation and HO-1 expression.