Low-intensity monochromatic red LED light can improve shikonin productivity in long-term cultivated Lithospermum erythrorhizon Sieb. et Zucc. calli

Currently, global challenges require the search for alternative sources of phytochemicals used by Mankind throughout its history. Plant cell culture technology can provide efficient and sustainable sources of phytochemicals with reduced energy and carbon footprints. The first patented industrial process of cultivating calluses as sources of phytochemicals was based on the calli of Lithospermum erythrorhizon Siebold & Zucc (Boraginaceae). The high pharmacological activity of L. eryrthrorhizon is due to the content of the naphthoquinone shikonin. Despite the development of LED lighting technology, in-depth studies of the effects of light on the biosynthesis of shikonin in cell cultures have not been carried out. In the present work, the impact of artificial monochromatic and bichromatic LED light at wide ranges of intensities (50, 100, and 300 µmol m ^-2 s ^-1 ) on the growth and biosynthesis of caffeic acid derivatives (CADs) as well as shikonin and shikonofurans in long-term continuously cultivated L. erythrorhizon calli was investigated for the first time. Red light has the greatest growth-stimulating effect regardless of intensity. The most effective treatment for CADs productivity is red/blue and green light treatment. The most effective way to produce shikonin in long-term cultivated L. erythrorhizon calli is to use red light with an intensity of 50 µmol m ^-2 s ^-1 and increase the inductor concentration. It may also be assumed that the blue and green components of white light have a negative effect on shikonin biosynthesis because of the light-dependent shift in the biosynthesis of CADs.