Growth conditions modify the concentrations of bioactive caffeic acid derivatives, amino acids and the structure of <i>Plantago</i> leaves

Abstract

Plantago species are widely used in natural medicine, but the effect of growth conditions on the chemical content of leaves is poorly understood. Three species of Plantago and three varieties of Plantago major L. were grown in greenhouse and outdoors to investigate effects on the content and composition of three bioactive caffeic acid derivatives (BCAD) (plantamajoside, iso-plantamajoside and verbascoside), free amino acids (FAA) and leaf texture of the plants. High Performance Thin Layer Chromatography (HPTLC) was used for the quantification of the BCAD, amino acids were determined by High Performance Liquid Chromatography (HPLC) and a histochemical technique was used to study the physical structure of the plants. Plants grown outdoors were significantly richer in BCAD compared with greenhouse grown plants. The highest content was seen in outdoor grown Plantago major L. (45.15 ± 4.36 mg/g DW) and the lowest in greenhouse grown Plantago major 'Frills' (7.74 ± 0.96 mg/g DW). Conversely, amino acid concentrations were significantly greater for greenhouse grown plants compared with outdoor grown plants. The highest concentration was found in greenhouse grown P. major L. and Plantago major 'Rubrifolia' (8.66 ± 0.64 mg/g DW and 7.94 ± 0.97 mg/g DW, respectively), whereas the lowest was in Plantago lanceolata L. grown outdoors (0.73 ± 0.09 mg/g DW). The leaf texture of the plants grown outdoors and in the greenhouse was significantly different. This study underlines the importance of environmental and growing conditions for plants in order to obtain high concentrations of bioactive compounds either from a nutritional point of view or for use in natural medicine.