A suspension culture of the hormone autotrophic cell line of Aralia elata (Miq.) Seem. for production of oleanolic acid and flavonoids

The hormone autotrophic cell (HAC) line of Aralia elata grows quickly in vitro without a plant-growth regulator and is thus a potential platform cell line for high-value metabolite production. In this study, a suspension culture of this HAC line was established by optimizing the concentration of sucrose (30–90 g/L), the inoculation amount, and the strength of the Murashige and Skoog (MS) medium. Then, different concentrations of the elicitors methyl jasmonate (MJ; 0, 50, 100, 250, and 500 μmol/L) and salicylic acid (SA; 0, 10, 25, 50, 100 and 250 mg/L) were used to improve its oleanolic acid accumulation, and the precursors phenylalanine, sodium acetate, and cinnamic acid were screened to enhance flavonoid accumulation. The optimal conditions for HAC line growth were 1.0 g HACs suspended in 100 mL liquid MS medium (in a 250-mL flask) with the addition of 70 g/L sucrose, and the time-points for the highest accumulations of oleanolic acid and total flavonoids were 18 and 21 days, respectively. The treatment of HACs with 250 μmol/L MJ for 6 days or 25 mg/L SA for 3 days improved oleanolic acid accumulation efficiency by 1.597-times (12.065 μg/d) and 3.59-times (22.860 μg/d) that of the control, respectively. The most effective concentrations of the three precursors were 50 mg/L for phenylalanine and sodium acetate, and 5 mg/L for cinnamic acid. Of these, sodium acetate treatment for 14 days proved most effective, providing a total flavonoids content (4.124 mg/L) 1.87-times that of the control and an accumulation efficiency 2.37-times that of the control. Therefore, the most effective treatments for HACs after 10 days of culturing were 25 mg/L SA for 3 days and 5 mg/L sodium acetate for 14 days, which improve the accumulations of oleanolic acid and total flavonoids, respectively.