Antioxidant and antibacterial activities, mineral and essential oil composition of spearmint (Mentha spicata L.) affected by the potassium levels

Mint family is considered of great importance all over the world with increasing needs for cultivation under controlled environment, but only narrow information is available about their response in relation to potassium supplementation. The present study determines the effects of different potassium levels (K:275-300-325-350-375 mg/L) on the morphological and biochemical characteristics of spearmint (Mentha spicata L.). The results indicated that the middle K levels of 325 mg/L increased biomass dry matter content without differences on fresh weight. Mineral content was affected, mainly for the micronutrients. High K application increased spearmint polyphenols content and antioxidant activity (DPPH, FRAP), while K > 325 mg/L revealed oxidative stress (increased H2O2), followed by the activation of antioxidant enzymes (SOD, APX, CAT) providing protective action to the plant. The main essential oil components were carvone, limonene, 1,8-cineole, germacrene D, beta-pinene and beta-caryophyllene. Considering greater carvone content, the 325 mg/L K treatment could be appropriate for spearmint cultivation and production for essential oil uses, improving their antioxidant and antibacterial, activity against foodborne pathogens.