Influence of Cultivation and Post-harvest Treatments on the. Glucotropaeolin Content of Tropaeolum majus. E. Bloem. 1. , S. Haneklaus. 1. , J. Thiele. 1.
Influence of Cultivation and Post-harvest Treatments on the Glucotropaeolin Content of Tropaeolum majus E. Bloem1, S. Haneklaus1, J. Thiele1, M. Kleinwächter2, D. Selmar2, E. Schnug1 1
Institute of Plant Nutrition and Soil Science, Federal Agricultural Research Centre (FAL), Bundesallee 50, 38116 Braunschweig, Germany 2 Institute of Plant Biology, Technical University Carolo-Wilhelmina, Mendelssohnstr. 4, 38106 Braunschweig, Germany
The medicinal plant nasturtium (T. majus) is used traditionally to combat infections of the urinary tract because of its high glucotropaeolin (GTL) content. When leaves should be used as an exclusive source for a phytopharmaceutical, a minimum GTL concentration of about 160 µmol g-1 would be required to permit a daily intake of at least 130 mg GTL with only six tablets. Both, biotic and abiotic factors, as well as the post-harvest treatments influence the GTL content. The aim of the presented studies is to determine the influence on the GTL content of seed density, sulphur supply and the different genotypes used. In addition, comparative analysis of various post-harvest treatments, i.e. drying practices, had been performed. A seed density of 30 x 30 cm reduced the individual plant biomass by 30 - 50% in comparison to a density of 60 x 60 cm, but the total biomass was up to 2.3-fold higher per hectare. The GTL content of leaves was not influenced by seed density. The GTL content in different plant parts regresses in the order seeds ≥ buds > flowers > leaves > stems, corresponding to mean contents of 70, 65, 35, 23 and 13 µmol / g d.w. In soils with a low sulphur supply, sulphur fertilisation significantly increased the GTL content of leaves, stems, seeds and whole plants by 3.4, 4.3, 1.1 and 2.3 µmol / g d.w. per kg S, respectively. A comparison of different drying techniques showed that freeze-drying and drying in a ventilated kiln at 40° C preserved the GTL best. Unavoidable losses of intact GTL occur with higher drying temperatures and account for in medium 30% during drying at 60° C and were as high as 85% at higher drying temperatures of 80°C.
