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Two Carthamus tinctorius varieties (Jawhara and 104) were studied in order to investigate their natural dyes contents and biological activities. Obtained results showed that quinochalcone contents and antioxidant activities varied considerably as function of flowering stages. So flowers at fructification stage contained the highest carthamin content with the strongest antioxidant capacity with all assays (FRAP, DPPH, and chelating power methods). In parallel, we showed a decrease in the content of precarthamin. The quantitative variation of these molecules could be due to colour change of C. tinctorius flowers. Correlation analysis indicated that the ABTS method showed the highest correlation coefficients with carthamin and precarthamin contents, that is, 0.886 and 0.973, respectively. Concerning the regional effect, the contents of precarthamin and carthamin varied significantly (P < 0.05) at studied regions with the optimum production given by samples of Beja (902.41 μg/g DW and 42.05 μg/g DW, respectively, at flowering stage). During flowering, the antimicrobial activity of these two natural dyes increased where the maximum inhibitory effect mentioned with carthamin mainly against E. coli (iz = 25.89 mm) at fructification stage. Therefore, the increased frequency of resistance to commonly used antibiotics leads to the search for new effective natural drugs at food and pharmaceutical industries.

Thousands of polyphenolic compounds have been identified in various plants. Recently, a number of studies showed that beneficial effects of grapes are related to the presence of polyphenols, with multiple biological activities. The aim of this study was to compare the polyphenol profiles as well as biological activities of the seeds of four Tunisia cultivated grape cultivars, syrat, merlot, cabernet sauvignon and carignan. The total phenolic content of seed extracts varied between varieties and seemed to be correlated to the scavenging activity. Preliminary antibacterial results showed a good growth inhibitory activity of syrat cultivar against Staphylococcus epidermidis. To our knowledge, this is the first of such study being performed on this bacterium, known as a leading cause of Tunisian hospital-acquired infections. Gas Chromatography Mass Spectrometry analysis identified 20 polyphenol components, flavonoids being the most abundant in all extracts, followed by phenolic acids, resveratrol, tyrosol, and syringaldehyde. We also noticed a deficiency of three phenolic acid compounds (salicylic acid methyl ester, ferulic acid, Sinapic acid) as well as a flavonoid one (myricetin) in merlot cultivar, which could be responsible for its low antioxidant activity. These results will help in the selective exploitation of the seeds obtained from winemaking wastes, as well as in further pharmacological and/or in vivo investigations.