Abstract:

Objective: To investigate the effects of different exogenous substances on the content of secondary metabolites in
Arnebia euchroma Johnst hairy roots and consequently provide a theoretical basis for further development and utilization of
Arnebia euchroma Johnst hairy roots. Methods: The contents of secondary metabolites were measured by spectrophotometry
from Arnebia euchroma Johnst hairy roots cultured in the presence of AgNO3 alone and in combination with L-phenylalanine
or L-phenylalanine plus sodium acetate. Results: The contents of shikonin, total polyphenols and total flavonoids in hairy
roots cultured for 30 days at an AgNO3 concentration of 5 mg/L respectively increased by 6, 1.3, 1.8 times compared with
the control (CK). In addition, when AgNO3 concentration was 3 mg/L, the anthocyanin content reached its peak, a 1.4-fold
increase over the control. Peak contents of shikonin, anthocyanins and total flavonoids were observed after culture in the
presence of both 25 mg/L L-phenylalanine and 5 mg/L AgNO3, which were increased by 1.3, 2.4 and 2.2 times, respectively,
compared with the CK. The content of total polyphenols was not higher than that in the CK, but it was still the highest among
three treatment groups. The contents of shikonin and total polyphenols reached their highest levels at 50 mg/L among different
sodium acetate concentrations combined with 5 mg/L AgNO3 and 25 mg/L L-phenylalanine, whereas the highest content of
anthocyanin was observed when the sodium acetate concentration was 200 mg/L. The content of total flavonoids in hairy
roots with sodium acetate treatments at various concentrations was significantly lower than that of the control. Conclusion:
The addition of AgNO3 and L-phenylalanine can cooperatively promote the accumulation of secondary metabolites in
Arnebia euchroma Johnst hairy roots. Meanwhile, AgNO3, L-phenylalanine and sodium acetate can cooperatively promote
the accumulation of shikonin, polyphenol and anthocyanin, but significantly inhibit the accumulation of total flavonoids.

Key words: Arnebia euchroma (Royle) Johnst, hairy roots, secondary metabolites, elicitor, precursor