Antioxidant Capacity and Accumulation of Caffeoylquinic Acids in Arnica montana L. In Vitro Shoots After Elicitation with Yeast Extract or Salicylic Acid

<i>Arnica montana</i> L. is an important herbal medicinal plant that belongs to the family Asteraceae. This plant has been known for its medicinal uses for centuries. <i>A. montana</i> exhibits several pharmacological properties, including immunomodulatory, anti-inflammatory, anticancer, antioxidant, and antibacterial effects. For the first time, the impacts of the biotic elicitor yeast extract, and the abiotic elicitor salicylic acid on micropropagation, antioxidant potential, and accumulation of caffeoylquinic acids in arnica in vitro shoots were assessed. The results showed that yeast extract applied at 100 mg/L significantly promotes shoot multiplication, biomass yield, total phenolic content, and synthesis of caffeoylquinic acids compared to control untreated shoots. Flavonoid content was the highest in samples treated with 200 mg/L of yeast extract, although at this concentration the measured biometric parameters began to decrease. Salicylic acid at 100 µM was found to be effective in the induction of vigorous shoots, shoot height growth, and biomass accumulation; nevertheless, this elicitor downregulated the caffeoylquinic acid level, total phenolics, and flavonoids. Increasing the concentration of salicylic acid to 200 µM caused shoot multiplication and fresh biomass accumulation reduction. Both elicitors modulated the activity of antioxidant enzymes against oxidative stress. Overall, the use of these substances can improve the growth and biomass yield in <i>Arnica</i> in vitro shoots.