Effect of Drought and Salinity Stress on Total Phenolic, Flavonoids and Flavonols Contents and Antioxidant Activity in in vitro Sprout cultures of Garden cress (Lepidium sativum).

Abstract

This study was carried to evaluate the effect of drought and salt dtress on accumulation of phenolic, flavonoids and flavonols compounds in in vitro cultured sprouts of garden cress plant. Drought stresses were induced by supplementation of culture medium with different levels of polyethylene glycol (PEG) and mannitol and NaCl was used in various concentrations as salt stress. Extraction yield was clearly influenced by different concentrations of PEG, mannitol and NaCl added to culture medium using methanolic extract. The highest extraction yield from the cultured sprouts (48.4%) was observed with 40 g/l PEG. All treatments were better than the control in their phenolic compounds extracted by methanol. The amount of total phenolic varied in the different treatment, ranging from 1.66 mg galic acid /g dry weigh with 8% mannitol to 2.63 mg galic acid /g dry weigh with 20 g/l PEG. Cultured sprouts showed best results of flavonoids contents of methanolic extract at level of 60 mM NaCl followed by addition of mannitol at levels 6 and 8%. On the other hand, the highest flavonols content was observed in methanolic extract without any additions (control). Otherwise, among various drought and salinity treatments, the methanol extract of 90 mM NaCl showed the highest antioxidant activity determined by the DPPH or ABTS (57.2% and 73.4%, respectively) assays. The same treatment exhibited antioxidant activity higher than of BHA (49.0% and 65.8%, respectively)