Ag+ ions are effective elicitors for enhancing the production of phenolic acids and tanshinones in Salvia aristata Aucher ex Benth. hairy roots

Abstract Salvia aristata Aucher ex Benth., due to containing tanshinones and phenolic acids, two main groups of bioactive metabolites, is one of the most valuable medicinal plant species in Iran. In this study, for the first time, hairy root (HR) cultures were established from 14-day-old seedlings inoculated with Agrobacterium rhizogenes strain ATCC 15834. Additionally, the effects of elicitation with Ag+ ions (15 and 25 µM) were investigated on the growth indices and content of phenolic acids and tanshinones of HRs in a time-course experiment. The findings of this work showed that exposure of HRs to Ag+ at both concentrations caused significant increases in the levels of rosmarinic acid (1.34- to 1.43-fold of control) and salvianolic acid B (1.71- to 1.82-fold of control). Specifically, 7.25-, 7.78-, 6.47-, and 3.9-fold increases were attained in total tanshinone, tanshinone I, tanshinone II-A, and cryptotanshinone contents of HRs, respectively, after seven days of exposure to 25 µM Ag+ ions compared to the control groups. The analysis revealed that exposure to Ag+ ions significantly enhanced the secretion of tanshinones, notably tanshinone II-A (31.49 ± 0.65 µg mL− 1) by HRs into the culture medium. The changes in transcript levels of crucial genes in the biosynthesis pathways of phenolic acids (PAL, TAT, and RAS) and tanshinones (CPS and CYP76AH1) were associated with their contents in HRs under elicitation with Ag+ ions. Our findings confirmed the effectiveness of an elicitation strategy to improve metabolite production in HR cultures of S. aristata as potent natural sources of phenolic acids and tanshinones.