Comparative effects of sulfur and nitrogen fertilization and post‐harvest processing parameters on the glucotropaeolin content of Tropaeolum majus L.

Under natural conditions, the content of the bioactive compound glucotropaeolin in the vegetative tissue of Tropaeolum majus is too low to be used directly for the preparation of a mono‐drug. In the present study the influence of sulfur and nitrogen fertilization and the post‐harvest drying procedure on the glucotropaeolin content was evaluated in order to minimize losses of the active glucosinolate. In 2001, field experiments with three levels of nitrogen and sulfur fertilization were conducted on two different sites. Nitrogen fertilization had no consistent influence on the glucotropaeolin content while sulfur fertilization with 100 kg S ha^?1 enhanced the glucotropaeolin content in leaves and seeds significantly by factors of 1.4–2.1 and 1.6–1.8, respectively. The results of the post‐harvest treatment showed that a gentle drying procedure at 40°C in a ventilated oven induced an increase in the glucotropaeolin content in leaves of 1.4–3.2‐fold (from 10.7–25.5 to 30.9–44.6 µmol g^?1 dry weight) compared to sampling in liquid nitrogen followed by freeze‐drying of the samples. This paper delivers new insights into glucosinolate metabolism that will contribute significantly not only to warrant a high content of bioactive compounds in medicinal plants, but also to promote glucosinolate concentrations in various crops by appropriate post‐harvest treatments. Copyright © 2007 Society of Chemical Industry