Effect of salinity on plant growth and biological activities of Carthamus tinctorius L. extracts at two flowering stages

In the present study, we were interested in the effect of salt stress on phenolic and carotenoid contents, antioxidant and antimicrobial activity of two varieties of Carthamus tinctorius (Jawhara and 104) flowers. For this purpose, C. tinctorius flowers from plants grown under four saline treatments (0, 5, 10 and 15 g/L NaCl) were collected at two development stages. As salinity increased up to 10 g/L, results showed that total phenols, flavonoids, condensed tannins and carotenoid contents increased with salinity. Such variability might be of great importance in terms of valorizing this plant as a source of naturally secondary metabolites. Furthermore, our results showed an enhancement of antioxidant activity which was evaluated by four different test systems (DPPH, beta-carotene-linoleic acid, chelating and reducing power assays) with increasing stress severity. Obtained results showed that, for the two varieties, salt effect was more pronounced at post flowering stage than full flowering one. The sensitivity test of the methanolic extracts of the harvested flowers was applied against seven human pathogenic bacteria and three yeast strains. Salinity reduced significantly the antimicrobial activity of flower extracts.