Major polyphenols in aerial organs of greater plantain (Plantago major L.), and effects of drying temperature on polyphenol contents in the leaves

Plantago major L. (common plantain) has been used in folk medicine all over the world, mainly for the healing of wounds. This species already has a high market demand in Asia, and attempts to domesticate P. major as a medicinal crop in horticulture are emerging also in Europe. Both polysaccharides and polyphenols have been proposed to have bioactive effects. In this study, major phenols were analysed in leaves, flower stalks and seeds of P. major plants from five homogenous offspring families, as verified by DNA-marker analysis. Furthermore, leaves were harvested and dried at different temperatures. The contents of plantamajoside, verbascoside and a hitherto unidentified compound, P1, differed greatly between plant organs. Degradation of leaf polyphenols increased with an increase in drying temperature, and consequently, freeze-drying resulted in the highest content of phenols. Thus it is important to select plant material of a suitable organ or combination of organs, and to use the lowest possible drying temperature to obtain a high content of a specific phenolic compound in P. major.

► Contents of polyphenols vary in different plant organs and genotypes of plantain.
► Contents of plantamajoside and verbascoside are highest in flower stalks.
► The polyphenols in plantain are sensitive to drying temperature.