Accumulation of Phenolic Compounds in Microshoot Cultures of Rhododendron tomentosum Harmaja (Ledum palustre L.)

Rhododendron tomentosum Harmaja is a marsh plant known for its high content of bioactive components, including essential oil, flavonoids, and phenolic acids. In the current work, the effects of cultivation mode (agar, liquid stationary, shake flask, and temporary immersion) and experiment duration (30, 60, and 90 days) on the growth and contents of non-volatile phenolics in Rhododendron tomentosum microshoots were investigated. Agar and liquid stationary cultures provided the highest dry biomass yield per liter, but their dry weight productivities per day were the lowest among the tested systems. Agitated and temporary immersion cultures, on the other hand, were the most productive in terms of fresh and dry biomass yield per day. LC-DAD-ESI-MS analysis of extracts from microshoots and wild-grown plants revealed similarities in phenolic composition: in both cases, the presence of catechin, chlorogenic acid, and flavonoids of flavonol type (mainly glycosides of quercetin and myricetin) was confirmed. The qualitative composition of the phenolic fraction was not affected by experiment duration and cultivation mode. As determined by HPLC analysis, shake flask and temporary immersion cultures were characterized by the highest phenolic contents: up to 37.5 and 26 mg/g dry weight, respectively. The maximum productivities of the above systems were equal to 18 and 13.5 mg/L/d, respectively.