Artificial monochromatic red and green light induces the biosynthesis of rosmarinic acid in long-term cultured calli of Mertensia maritima (L.)

Rosmarinic acid is a metabolite that improves cognitive function and may prevent the development of Alzheimer's disease. The long-term continuous cultured calli of the extreme halophytic plant Mertensia maritima L. (Boraginaceae) constitute a source of rosmarinic acid. However, the biosynthetic activity of this calli culture gradually decreased over 12 years of continuous cultivation. In this work, we have shown that this process can be overcome by using monochromatic light, especially green light, in the wavelength range of 510–520 nm. In recent years, LEDs (light-emitting diodes) have been the subject of research within the fields of plant growth, development, and phytochemical biosynthesis. As determined by HPLC–DAD-ESI-HRMS, when this culture was exposed to normal (100 µmol m⁻² s⁻¹) or moderate (300 µmol m⁻² s⁻¹) green light, the content of rosmarinic acid increased by 2 and 3.5 times, respectively. A green light-induced increase in the content of rosmarinic acid was accompanied by the inhibition of the biosynthesis of glucosides of coumaric and ferulic acid, which are also produced in long-term cultured calli of M. maritima. Thus, monochromatic light can be used to increase the biosynthetic capacity of callus cultures during long-term cultivation.