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Preliminary analysis of antioxidant activity and colour of water soluble extract from Tunisian Deglet Nour and Allig palm date seeds

Mohamed Ali Bouaziz, Hamadi Attia, Souhail Besbes, Christophe Blecker

The antioxidant activity and phenolic content of water soluble extracts (WSE) of date seeds from Deglet Nour and Allig varieties were studied. Total phenolic contents inWSE ofDegletNour andAllig seedswere, in dry weight, 38.34 mg GAE /g and 37.78 mg GAE /g, respectively. Free radical scavenging activities of WSE were assessed using 2,2-diphenyl-1- picrylhydrazyl (DPPH).WSE pigments showed an excellentDPPH radical scavenging activity with 75-78% of inhibition. The variation in colour of WSE pigments of date seeds have been evaluated over pH range 2-10. The study was made on crude extract. The pigment directly from Deglet Nour andAllig date seeds can be dissolved in alkaline and acidic waters solutions. The WSE pigments of date seeds showed much redder colour at alkaline solution than the acidic solution. The colour was reversible with pH variation. No significant difference between the UV-Visible absorbance of the Deglet Nour and Allig seed WSE. When varying pH from acidic to alkaline values, a progressively apparition of two peak in the visible wavelength was observed while no noticeable change was observed in the UV absorbance wavelengths for the two studied varieties. A concomitant increase in the intensity of theUV absorptionwavelengthwas also observed for DegletNour andAllig seeds. The red-brown taint obtained in the neutral and alkaline pH values may allow the studiedWSE pigments of date seeds compound to be regarded as a possible colorant for some slightly redbrown coloured neutral and alkaline products.