Química medicinal

Differential Responses of Cakile maritima at Two Development Stages to Salinity: Changes on Phenolic Metabolites and Related Enzymes and Antioxidant Activity

Abstract

Rim Ben Mansour, Sara Dakhlaouia, Wissal Msahli, Riadh Ksouri and Wided Megdiche-Ksouri

Though halophytes are naturally adapted to salinity, their salt-tolerance limits are greatly influenced by endogenous (that is, physiological development stages) and exogenous factors (that is, salinity). In this work, the evaluation of oxidative stress, bioactive molecules contents, antioxidant activities and two enzymes involved in the synthesis of secondary metabolites were assessed in the edible halophytic species Cakile maritima as function of salinity (0, 100, 400 mM NaCl) and two physiological stages. Total phenols, flavonoids and tannin contents increased by 58, 80 and 18% in vegetative period and by 27, 28 and 31% in flowering one at 400 mM NaCl, respectively as compared to C. maritima shoots control. These data indicated that phenolic compounds played an important role in protecting this species from salinity. The stimulatory effect of the salt on the total phenols content leads to the investigation of the role of two regulatory shikimate/phenylpropanoid pathway enzymes in phenolic synthesis. Results indicated that increased treatment progressively stimulated positively the activities of phenylalanine ammonia lyase and shikimate kinase in the vegetative and flowering period. Increasing salinity is correlated to the accumulation of carotenoids, anthocyanin, proline and ascorbate contents. The antioxidant activity enhanced at the vegetative stage in salt condition as compared to the flowering one. These results strongly indicate that salinity induces the accumulation of secondary metabolites in C. maritima shoots by altering the phenolic synthesis enzymes, as well as for the up-regulation of antioxidant molecules defense.