The Protective Function and Modification of Secondary Metabolite Accumulation in Response to Light Stress in Dracocephalum forrestii Shoots

Abstract

The aim of this work was to determine the effect of stress conditions caused by different light sources, i.e., blue LED (λ = 430 nm), red LED (λ = 670 nm), blue and red LED (70%:30%) and white LED (430–670 nm) on the growth and morphology of cultivated in vitro Dracocephalum forrestii shoot culture. It also examines the effects on bioactive phenolic compound production and photosynthetic pigment content, as well as on antioxidant enzyme activity (CAT, SOD, POD) and antioxidant properties. The most beneficial proliferation effect was observed under white LEDs (7.1 ± 2.1 shoots per explant). The white and blue lights stimulated the highest fresh weight gain, while red light induced the highest dry weight gain. The total phenolic acid content ranged from 13.824 ± 1.181 to 20.018 ± 801 mg g DW−1 depending on light conditions. The highest content of rosmarinic acid was found in the control shoots (cultivated under fluorescent lamps), followed by culture grown under red light. All LED treatments, especially red and blue, increased salvianolic acid B content, and blue increased apigenin p-coumarylrhamnoside biosynthesis. The greatest ferric reduction activity was observed in shoots cultivated under red light, followed by blue; this is associated with the presence of the highest total phenol content, especially phenolic acids. Similarly, the highest DPPH radical scavenging potential was observed under red light followed by blue. This study proves that LEDs have emerged as significant support for directed in vitro propagation, taking advantage of specific stress responses on various light spectra. This study also showed how stress induced by different LED light spectra increases in Dracocephalum forrestii the synthesis of pharmacologically-active compounds. Hence, light stress may turn out to be a simpler alternative to metabolic engineering for improving the production of secondary metabolites of therapeutic value.

The Effect of the Stress-Signalling Mediator Triacontanol on Biochemical and Physiological Modifications in Dracocephalum forrestii Culture

“…The levels of polyphenolic compounds in D. forrestii shoots grown for five weeks on MS agar media supplemented with TRIA alone and with TRIA + BAP + IAA were evaluated. The levels of the phenolic acids present in the hydromethanolic extract were determined based on their retention times and UV and MS spectra, as described previously [ 18 ]. The quantities were determined using HPLC.…”

“…The plant material used in the experiment was D. forrestii shoots cultured under previously-established optimal conditions, i.e., on an MS [ 40 ] agar medium with 0.5 mg/L BAP and 0.2 mg/L IAA [ 18 ]. The nodal segments of shoots (about 0.5–1 cm in length) were used as explants.…”

“…This species grows in mountainous areas, over 2000 m above sea level, and its aboveground parts are traditionally used in folk medicine as an astringent, diuretic, and antipyretic factor [ 16 , 17 ]. D. forrestii shoot culture is a valuable source of polyphenolic compounds, particularly phenolic acids (e.g., rosmarinic acid, caffeic acid, chlorogenic acid, salvianolic acid B) [ 18 ]. The presence of these compounds in plant material determines its antioxidant, antimicrobial, and antitumor properties [ 19 ].…”

In Vitro Strategy for the Enhancement of the Production of Bioactive Polyphenols in Transformed Roots of Salvia bulleyana

“…LED treatments have also been reported to enhance the biosynthesis of bioactive metabolites in vitro [ 45 , 46 ]. It was observed that light could regulate the expression of genes responsible for the biosynthesis of the phenylpropanoid pathway enzymes that synthesize polyphenolic acids [ 46 , 47 ].…”

“…The presence of blue light significantly increased the PAL (phenylalanine ammonia-lyase) activity in strawberry fruits [ 46 ], the initial step enzyme of the polyphenol pathway, as well as other enzymes, including shikimate dehydrogenase, tyrosine ammonia-lyase, cinnamate-4-hydroxylase, 4-coumarate/coenzyme A ligase, chalcone synthase, dihydroflavonol-4-reductase, and flavanone-3-β-hydroxylase. Blue light has been found to stimulate the production of polyphenolic acids in some Lamiaceae species, such as Ocimmum basilicum , Agastache rugose , or Dracocephalum forrestii [ 45 , 48 , 49 ].…”