Light Quality Modulates Growth, Triggers Differential Accumulation of Phenolic Compounds, and Changes the Total Antioxidant Capacity in the Red Callus of Vitis davidii

Influence of Different Precursors on Content of Polyphenols in Camellia sinensis In Vitro Callus Culture

Plant tissue cultures are considered as potential producers of biologically active plant metabolites, which include various phenolic compounds that can be used to maintain human health. Moreover, in most cases, their accumulation is lower than in the original explants, which requires the search for factors and influences for the intensification of this process. In this case, it is very promising to use the precursors of their biosynthesis as potential "regulators" of the various metabolites' formation. The purpose of our research was to study the effect of L-phenylalanine (PhA, 3 mM), trans-cinnamic acid (CA, 1 mM) and naringenin (NG, 0.5 mM), as components of various stages of phenolic metabolism, on accumulation of various phenolic compound classes, including phenylpropanoids, flavans and proanthocyanidins, as well as the content of malondialdehyde in in vitro callus culture of the tea plant (Camellia sinensis L.). According to the data obtained, the precursors' influence did not lead to changes in the morphology and water content of the cultures. At the same time, an increase in the total content of phenolic compounds, as well as phenylpropanoids, flavans and proanthocyanidins, was noted in tea callus cultures. Effectiveness of precursor action depends on its characteristics and the exposure duration, and was more pronounced in the treatments with PhA. This compound can be considered as the most effective precursor regulating phenolic metabolism, contributing to a twofold increase in the total content of phenolic compounds, flavanes and proanthocyanidins, and a fourfold increase in phenylpropanoids in tea callus cultures.

Phenolic Acids and Amaryllidaceae Alkaloids Profiles in Leucojum aestivum L. In Vitro Plants Grown under Different Light Conditions

Light-emitting diodes (LEDs) have emerged as efficient light sources for promoting in vitro plant growth and primary and secondary metabolite biosynthesis. This study investigated the effects of blue, red, and white-red LED lights on plant biomass growth, photosynthetic pigments, soluble sugars, phenolic compounds, the production of Amaryllidaceae alkaloids, and the activities of antioxidant enzymes in Leucojum aestivum L. cultures. A white fluorescent light was used as a control. The plants that were grown under white-red and red light showed the highest fresh biomass increments. The blue light stimulated chlorophyll a, carotenoid, and flavonoid production. The white-red and blue lights were favourable for phenolic acid biosynthesis. Chlorogenic, p-hydroxybenzoic, caffeic, syringic, p-coumaric, ferulic, sinapic, and benzoic acids were identified in plant materials, with ferulic acid dominating. The blue light had a significant beneficial effect both on galanthamine (4.67 µg/g of dry weight (DW)) and lycorine (115 µg/g DW) biosynthesis. Red light treatment increased catalase and superoxide dismutase activities, and high catalase activity was also observed in plants treated with white-red and blue light. This is the first report to provide evidence of the effects of LED light on the biosynthesis of phenolic acid and Amaryllidaceae alkaloids in L. aestivum cultures, which is of pharmacological importance and can propose new strategies for their production.