The Influence of Exogenous Phenylalanine on the Accumulation of Secondary Metabolites in Agitated Shoot Cultures of Ruta graveolens L.

Abstract

This study aimed to examine the influence of the addition of a precursor (phenylalanine) on the accumulation of secondary metabolites in agitated shoot cultures of Ruta graveolens. Cultures were grown on Linsmaier and Skoog (LS) medium, with plant growth regulators (0.1 mg/L α-naphthaleneacetic acid—NAA—and 0.1 mg/L 6-benzylaminopurine—BAP). Phenylalanine was added to the cultures at a concentration of 1.25 g/L after 4 and 5 weeks of growth cycles. Biomass was collected after 2, 4, and 7 days of precursor addition. Both control and experimental cultures had the same secondary metabolites accumulated. Using the HPLC method, linear furanocoumarins (bergapten, isoimperatorin, isopimpinellin, psoralen, and xanthotoxin), furoquinoline alkaloids (γ-fagarine, 7-isopentenyloxy-γ-fagarine, and skimmianine), and catechin were detected and quantified in the methanolic extracts. In turn, phenolic acids, such as gallic acid, protocatechuic acid, p-hydroxybenzoic acid, syringic acid, p-coumaric acid, and ferulic acid were detected in hydrolysates. The production of phenolic acids and catechin (1.5-fold) was significantly increased by the addition of precursor, while there was no significant effect on the production of coumarins and alkaloids. The highest total content of phenolic acids (109 mg/100 g DW) was obtained on the second day of phenylalanine addition (the fourth week of growth cycles). The dominant phenolic compounds were p-coumaric acid (maximum content 64.3 mg/100 g DW) and ferulic acid (maximum content 35.6 mg/100 g DW). In the case of catechins, the highest total content (66 mg/100 g DW) was obtained on the third day of precursor addition (the fourth week of growth cycles). This study is the first to document the effect of feeding the culture medium with phenylalanine on the accumulation of bioactive metabolites in in vitro cultures of R. graveolens.