Copper-induced changes in nutrient uptake, enzymatic and non-enzymatic antioxidant systems in horehound ( Marrubium vulgare L.)

Background: The effect of different concentrations (80, 200 and 300 mg/L) of copper (Cu2+) on physiological parameters of horehound (Marrubium vulgare L.) was studied. Once Horehound was cultivated in pots, element uptake and antioxidant system efficiency have been evaluated. Questions: What is the effect of copper on the physiological parameters of Marrubium vulgare? What are the defense strategies developed by this plant to overcome cupric stress? Species study: horehound (M. vulgare) medicinal plant from the family of Lamiaceae. Study site and dates: Seeds of M. vulgare were issued from a non contaminated wild population in the region of Beja (Northwestern Tunisia). Culture of M. vulgare was conducted in 1 August 2014 and lasted 4 months. Methods: The Cu, Fe, K, Mg and Ca contents have been determined. Total phenolic and flavonoid contents have been determined. The free radical scavenging activity (DPPH test) together with SOD, CAT and APX antioxidant enzymatic activity have been evaluated. Results: In the aerial part extracts, Copper stress reduced the uptake and translocation of the cationic elements Fe2+, K+ and Ca2+, in a Cu2+ concentration-dependent manner. The treatment with copper gives rise to positive effects on antioxidant enzymes activities (SOD and CAT enzymes) and to an increase of total phenol and flavonoid contents. Unexpectedly, no correlation with the anti-radical scavenging activity was observed. Conclusions: Marrubium vulgare possess an intrinsic capability to cope with the Cu stress by activation of the enzymatic and non-enzymatic antioxidant systems.