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

Salvia aristata Aucher ex Benth. is considered a valuable endemic medicinal plant in Iran due to its two main bioactive metabolites: phenolic acids and tanshinones. This study established hairy root (HR) cultures from 14-day-old seedlings inoculated with Rhizobium rhizogenes strain ATCC 15834. In addition, the effects of elicitation with Ag⁺ ions (15 and 25 µM) on growth indices, phenolic acid and tanshinone contents in the HRs, as well as changes in the expression patterns of key genes involved in their biosynthetic pathways were investigated in a time-course experiment. The results showed that exposure of HRs to both Ag⁺ ions concentrations significantly increased rosmarinic acid (1.34- to 1.43-fold) and salvianolic acid B (1.71- to 1.82-fold) content. Notably, exposure to 25 µM Ag⁺ ions for seven days resulted in increases of 7.25-, 7.78-, 6.47-, and 3.9-fold in total tanshinones, tanshinone I, tanshinone IIA, and cryptotanshinone levels, respectively, compared to the control groups. The study also revealed a significant increase in the release of tanshinones, especially tanshinone IIA (31.49 ± 0.65 mg L⁻¹) by HRs into the culture medium following Ag⁺ ions elicitation. Changes in the transcription levels of key genes related to the biosynthetic pathways of phenolic acids (PAL, TAT, and RAS) and tanshinones (CPS and CYP76AH1) were also associated with their contents in the elicited HRs. The findings confirm the effectiveness of elicitation as a strategy to enhance metabolite production in HR cultures of S. aristata, a potent natural source of phenolic acids and tanshinones.