Effect of water deficit stress on yield characteristics, antioxidant capacity and metabolite profile of peppermint (Mentha piperita L.)

Medicinal Plants are almost reach sources of natural antioxidants such as terpenoids and phenolic compounds and have great potential as an alternative for synthetic antioxidants against oxidative stresses. Peppermint (Mentha piperita) infusion is a valuable worldwide source of antioxidants. The antioxidant property can be enhanced by inducing abiotic stresses. This experiment was conducted to evaluate prolong (4 months) water deficit stress (no stress, mild stress and severe stress as 100, 75 and 50% of field capacity, respectively) on cultivated peppermint on plant growth, secondary metabolite profile and antioxidant capacity of peppermint infusions. Both water deficit stress treatment decresed plant height, leaf wet and dry weight and leaf size significantly. Also, water deficit stress increased antioxidant capacity, total phenolic and flavonoid contents significantly. Some phenolic compounds such as quercetin, coumaric acid and luteolin were detected only in water-deficit conditions. Also, the amount of some identified amino acids and unsaturated fatty acids were changed under water deficit stress. Therefore, inducing water stress can enhance the biological value of peppermint and improve bioactive compounds and the antioxidant capacity of peppermint extract.