Silver nitrate and silver nanoparticles for enhancing the caffeic acid derivates production in cell suspension culture of Lactuca undulata Ledeb

Lactuca undulata Ledeb. is a medicinal plant belonging to the Asteraceae family. Chicoric acid is one of the main derivatives of caffeic acid, with various pharmacological and biological properties. This study was conducted to optimize cell suspension culture and enhance chicoric acid production in L. undulata by eliciting secondary metabolites using silver nitrate (AgNO3) and silver nanoparticles (AgNPs). Seeds were cultured on ½ MS medium to produce sterile seedlings. In order to produce callus, leaf and root explants were obtained from 2 months old sterile seedlings and placed on ½ MS medium containing 2 mg/L 2,4-D/ plus 0.5 mg/L Kin and 2 mg/L 2,4-D/ plus 2 mg/L Kin, respectively. Cell suspension cultures from leaf and root-derived calluses were established and treated with different concentrations (0, 2, and 4 mg/L) of AgNO3 and AgNPs during the logarithmic growth phase. Then cells were harvested after 24, 48, and 72 hours. Overall, elicitation by AgNPs was more effective on chicoric acid production compared to AgNO3. The highest amounts of chicoric acid (9.7 ± 0.48 mg/g DW) and caffeic acid (15.3 ± 0.8 mg/L) were found in leaf and root cell suspension cultures after 48 hours of exposure to 4 and 2 mg/L AgNPs, respectively. In contrast, 4 mg/L of AgNO3 stimulated the greatest accumulation of chlorogenic acid (4.56 ± 0.3 mg/g DW) in root cell culture at 72 h after elicitation. The current results revealed that the use of AgNPs can be an efficient strategy to improve cichoric acid accumulation in cell suspension culture.