Lichen-derived elicitors (Evernia prunastri extract and usnic acid) enhance phenolic compound accumulation in agitated shoot cultures of Lychnis flos-cuculi
Lychnis flos-cuculi L. is a plant species valued for its rich content of phenolic compounds and traditional therapeutic applications; however, the decline of natural populations necessitates the development of alternative biomass sources. The present study investigated the effect of biotic elicitation with Evernia prunastri (L.) Ach. thallus extract and usnic acid on phenolic compound accumulation in in vitro shoot cultures of L. flos-cuculi. Shoots were cultivated in liquid Murashige and Skoog medium under shake-flask conditions and treated with E. prunastri thallus extract (1 mg/mL–3 mg/mL) or (+)-usnic acid previously isolated from E. prunastri (6.25–25 µM) for 24, 72, 144, and 192 h. The concentrations of selected phenolic acids and flavonoids were determined by HPLC-DAD. The elicitation treatments did not adversely affect shoot morphology or physiological status; however, biomass growth generally decreased with increasing elicitor concentration and exposure time. Four phenolic acids (caffeic, ferulic, p-coumaric, and protocatechuic acids) and three flavonoids (apigenin, luteolin, and vitexin) were identified in the shoot biomass. The highest phenolic acid accumulation following elicitation with E. prunastri thallus extract was confirmed after 192 h at 3 mg/mL, particularly for p-coumaric acid (14.21 mg/100 g DW). Usnic acid proved to be an effective elicitor of flavonoid biosynthesis, resulting in the highest apigenin content (17.81 mg/100 g DW) after 192 h treatment with 25 µM usnic acid. The results demonstrate that biotic elicitation with lichen-derived compounds effectively enhances the production of valuable phenolic metabolites in L. flos-cuculi in vitro cultures. Therefore, agitated shoot cultures represent a promising sustainable source of bioactive compounds for pharmaceutical and biotechnological applications. Biotic elicitation with Evernia prunastri extract and usnic acid enhanced the accumulation of phenolic acids and flavonoids in Lychnis flos-cuculi in vitro shoot cultures.