Developmental and chemical characteristics of Melittis melissophyllum L. in limited access of sunlight

Summary Introduction: Bastard balm grows in forests, in central and southeastern part of Europe. The herb of this species is rich in phenolics, mainly flavonoids, phenolic acids and coumarins. The plant is used in traditional European medicine, in digestive problems and for aromatizing tobacco and alcohol products. Objective: The purpose of this study was to determine the influence of shading on bastard balm development and the accumulation of phenolics in its herb, with special respect to coumarin as a quality marker of this raw material. Methods: The plants were cultivated in full sunlight, in 30% and 50% shade provided by shading nets. The herb was harvested from plants in the third year of vegetation, at four subsequent developmental stages and then subjected to chemical evaluation. In the raw material, the total contents of flavonoids, phenolic acids and coumarins was determined. The content of coumarin was analyzed using HPLC-DAD. Results: Plants grown in 30% shade produced the highest number of flowers and seeds. They produced the highest mass of herb at the beginning of the seed-setting stage. The plants grown in full sunlight revealed the highest content of flavonoids and phenolic acids, especially during flowering and at the beginning of the seed-setting stage. The mass of herb obtained by plants cultivated at deep (50%) shade was the lowest, however, the content of coumarin in these plants was the highest. Conclusion: The influence of shade on bastard balm was expressed by the herb mass and coumarin content increment. The plants thrived best in 30% shade, both in terms of flowering abundance and the mass of herb, whereas those from 50% shade were the richest in coumarin.