Chilling and salinity increase extractable antioxidants in cell suspension cultures of the sow thistle, Sonchus oleraceus L.

Cell suspension cultures of Sonchus oleraceus L. provide a continuous, efficient system for the production of low molecular weight antioxidants (LMWAs) unhindered by climatic and phenological effects. Because climatic and edaphic factors are known to increase LMWA levels in intact plants, our aim was to study possible effects of abiotic stressors on extractable LMWA activities in vitro. Cell cultures were initiated from in vitro shoots obtained from seedlings of two ecotypes originating from Acacia Bay (ACB) and Oamaru (OAM) in New Zealand. Cells were exposed to chilling, salinity or the combination of both, and concentrations of principal phenolic compounds measured in cell extracts. The cell suspensions yielded higher concentrations of phenolic LMWAs as compared with leaf extracts from in vivo plants. All stressor treatments increased LMWA activities and concentrations of total phenolics, ascorbate and chlorogenic acid relative to the controls. For OAM, all stressors were equally effective; for ACB, the chilling x salinity combination had the greatest effect. Extracts of ACB cells were consistently richer sources of LMWAs than were those from OAM, irrespective of the stressor. The data indicate that the judicious use of abiotic stressors can effectively augment key antioxidant yields from S. oleraceus cell suspensions.