Salinity effects on growth, essential oil yield and composition and phenolic compounds content of marjoram (origanum majorana l.) leaves

The effect of irrigation with different NaCl levels (0.9, 5 and 10 ds/m) on growth, essential oil yield and composition, in addition to polyphenol content of Tunisian marjoram (Origanum majorana L.) leaves was investigated. Plant growth and chlorophyll content were significantly decreased with increasing NaCl levels. The essential oil yield increased significantly up to 55.5% with 5 ds/m NaCl and decreased significantly at high salinity. Terpinene‐4‐ol, γ‐terpinene, cis‐sabinene‐hydrate and α‐terpineol were found as the main volatile compound of marjoram leaf essential oil. Further, salinity effect was highly significant for the content of these compounds and depending on the treatment level. The most represented class was monoterpene alcohols (870.6 µg/g dry weight [DW]) represented by terpinene‐4‐ol (555.1 µg/g DW) and remains the major one at different salt levels, followed by monoterpene hydrocarbons (335.54 µg/g DW). Moreover, salinity affected differently phenolic compounds content of marjoram leaves. PRACTICAL APPLICATIONS: This work was carried out as a first step for a chemical and biological activity of Tunisian Origanum majorana through phenolic and essential oil composition. A further identification, isolation and purification of O. majorana phenolics and volatiles will be associated to an application in food industry as antioxydants, additives for food preservation and for enhancing their nutritional value and organoleptic quality. This study could be continued by the investigation of the antimicrobial activity of O. majorana bioactive compounds with the purpose of an eventual use to prevent growth of many foodborne and food spoilage microorganisms in foods. Furthermore, a pharmacological study could be established through in vivo assays in order to discover new anticarcenogenic, antinflammatory, antimutagenic and other activities of O. majorana. Such results could be used in pharmaceutical formulations leading to new human drugs from this medicinal plant.