Department of Biology

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    Caractérisation phytochimique de l’orge nue hydroponique, analyse du potentiel antioxydant et étude de la tolérance au stress salin.
    (2024) Bechiri Romayssa
    T he effect of salinity on morpho-physiological and biochemical parameters was studied in nine varieties, three varieties of durum wheat (AinLahma, Cirta, Wahbi), three varieties of soft wheat (Boumrzougue, Akamoukh, Massin) and two varieties of dressed barley (Saida, Barbrous) including the new variety of naked barley (Chaiirennabi), under three concentrations (4.2g/l, 6g/l and 12g/l) of NaCl in a hydroponic culture. The response of these nine varieties and with a comparative analysis of morphological, physiological and biochemical parameters, it was noted that there is a positive correlation between leaf area, relative water content and total chlorophyll content, as well as a correlation regarding the variety-treatment interaction. However, salt treatment caused a decrease in plant height, number of leaves, leaf area and specific leaf surface area, fresh and dry weight of roots. The results showed a better tolerance to salinity of the Barbarous (Ob) barley variety. This tolerance was manifested by the lowest decrease in biomass, number of leaves, leaf area, chlorophyll "a" and chlorophyll "b" contents and specific leaf surface area and root length, and a high increase in proline. The aim of this quantitative and qualitative study is to compare the new naked barley variety with other cereals. Regarding the richness in phytonutrients mainly including flavonoids, polyphenols, condensed tannins, the antioxidant power was tested according to the DPPH method of free radical scavenging. The results obtained from the quantitative study of methanolic extracts show that varieties rich in tannins and flavonoids have a significant antioxidant activity compared to a variety rich only in total polyphenols. The results reported the existence of a very highly significant difference (P < 0.001) between the mean inhibition concentrations (IC50) of the new variety ChaiirEnnabi (naked barley) compared to ascorbic acid, which shows a low antioxidant activity of this variety. The Barbarous barley variety (dressed barley) is the only variety that has an IC50 does not differ statistically with the ascorbic acid reference with a significant inhibition percentage (76.49%) therefore a significant antioxidant activity, and high contents of polyphenols, flavonoids and even tannins. The results obtained show that the phytochemical composition varies greatly between the different cereal samples analyzed, and confirm that the antioxidant activity (DPPH or percentage of inhibition) is more correlated with the content of phenolic compounds. Qualitative studies based on high performance liquid chromatography (HPLC) of these compounds allow us to visualize phenolic traces of our extracts. The different peaks in the different chromatographic profiles can be classified into three phenolic groups which are: Flavone derivatives (Catechin, rutin, keampherol), cinnamic acid derivatives (ferulic acid, P.Coumaric acid, O.Coumaric acid), and benzoic acid derivatives (protocatechuic acid, benzoic acid, vanillic acid, gallic acid; the latter seem to be the majority). For the naked barley variety, the methanolic extract also contains substances belonging to the flavone and flavonol family, as well as phenolic acids. Keampherol, keampherol glycosyl, pholoroglucinol, vanillic acid are the main molecules identified in this variety and potentially interesting for their biological properties.