Effects of Metformin on Antioxidative Response of Lactuca sativa Plants

The occurrence of pharmaceuticals in the ecosystems is considered of growing concern since these compounds may affect different organisms, causing changes on their metabolism and possibly contributing to food chain contamination. These are undesirable consequences from the increase consumption of pharmaceuticals.
Our study aims to understand how lettuce cope with two pharmaceuticals, acetaminophen (ACT) and metformin (MTF), evaluating the oxidative stress and the effect on metabolism.
Lettuce was produced in a hydroponic culture contaminated with ACT and MTF separately. After 1, 8 and 15 days plants were harvested and analysed.
Under ACT, roots presented more significant differences in H₂O₂ and MDA contents than leaves, mainly on day 8 an increase on concentrations was observed for both compounds. However, the enzymes SOD, CAT and GPOD revealed higher activities ratio in leaves than in roots. The glutathione cycle enzymes showed significant increases on roots of day 8, while in leaves a decrease was observed on day 1.
Similar patterns on H₂O₂ and MDA were obtained under MTF contamination. However, the main differences were found on day 15. Antioxidative enzymes revealed different trends among tissues. SOD and CAT activity increased in leaves, along time of exposure. GPOD activity in roots showed more significant increases on the last day of exposure and in leaves significant differences were registered on days 1 and 8.
PAL and anthocyanins content showed a good correlation pattern, both increasing with ACT and MTF concentrations. Thus, both pharmaceuticals may affect anthocyanins production and, consequently, secondary metabolism regulation.
Although ACT and MTF interferes differently on the stress response mechanism, both compounds affect plants metabolism inducing oxidative stress. MTF seems to influence more the ascorbate pools and APX activity than ACT, while ACT shows more differences on GSH pools and GR activity.