EFFET DES DIFFERENTS MODES DE SECHAGE SUR LE CONTENU PHENOLIQUE ET BIOLOGIQUE D’UNE PLANTE SPONTANEE A CARACTERE MEDICINALE DU SAHARA SEPTENTRIONAL ALGERIEN

Abstract

This study focuses on the contribution to the optimization of the effect of different drying methods (open air, oven, solar dryer and freeze-drying in comparison with the fresh plant) of a spontaneous plant with a medicinal character in the Sahara. Northern Algerian (Cymbopogon schoenanthus) on the content of secondary metabolites. The determination of the yield of phenolic compounds showed the richness of the dry crude extracts in all the drying modes carried out compared to the fresh sample. The best yields are obtained with freeze-dried and steamed samples (15.45% and 11.5%) respectively. The dosage of some secondary metabolites revealed the presence of 1.111 mg EAG/g DM in polyphenols in the taxa dried in the solar dryer and 0.031 mg EQ/g DM in flavonoids in the air-dried samples and 0.061 mg EAG/g DM in tannins in steamed samples. The DPPH test. revealed the strong antioxidant activity of Cymbopogon schoenanthus when freeze-dried or sun-dried, their EC50s are 0.222 mg/ml and 0.412 mg/ml, respectively. This anti-radical activity would be linked to the temperature of their desiccation not exceeding 45°C. Lyophilization and the solar dryer allow the preservation or even the increase of the antioxidant activity of the extracts tested, translated by the reduction of the EC50. According to the different results obtained, it can be concluded that freeze-drying and solar dryer seem the most preservative of phenolic compounds and of the antioxidant activity of all the extracts investigated.