Long-term response on growth, antioxidant enzymes, and secondary metabolites in salicylic acid pre-treated Uncaria tomentosa microplants

Objective To obtain micro propagated Uncaria tomentosa plantlets with enhanced secondary metabolites production, long-term responses to salicylic acid (SA) pre-treatments at 1 and 100 A mu M were evaluated after propagation of the plantlets in a SA-free medium. Results SA pre-treatments of single node cuttings OF U. tomentosa produced long-term responses in microplants grown for 75 days in a SA-free medium. Reduction in survival rate, root formation, and stem elongation were observed only with 100 A mu M SA pre-treatments with respect to the control (0 + DMSO).Both pre-treatments enhanced H2O2 and inhibited superoxide dismutase and catalase activities, while guaiacol peroxidase was increased only with 1 A mu M SA. Also, both pre-treatments increased total monoterpenoid oxindole alkaloids by ca. 55 % (16.5 mg g(-1) DW), including isopteropodine, speciophylline, mitraphylline, isomitraphylline, rhynchopylline, and isorhynchopylline; and flavonoids by ca. 21 % (914 mu g g(-1) DW), whereas phenolic compounds were increased 80 % (599 mu g g(-1) DW) at 1 A mu M and 8.2 % (359 mu g g(-1) DW) at 100 A mu M SA. Conclusion Pre-treatment with 1 A mu M SA of U.tomentosa microplants preserved the survival rate and increased oxindole alkaloids, flavonoids, and phenolic compounds in correlation with H2O2 and peroxidase activity enhancements, offering biotechnological advantages over non-treated microplants.