Samenvatting

During this research project the influence of selenium enriched growing environment on the phenolic composition on several Allium species is studied. Besides this, the influence on morphological properties is also monitored. Folin-Ciocalteu method is used to determine the total phenolic content and High Performance Liquid Chromatography coupled to a Diode Array detector is used for polyphenol composition. Eighteen polyphenols (i.e. gallic acid; 3,4-dyhydroxybenzoic acid; 4-hydroxybenzoic acid; chlorogenic acid; caffeic acid; syringic acid; p-coumaric acid; ferulic acid; sinapic acid; hyperoside; rutin; myricetin; quercitrin; rosmarinic acid; quercetin; luteolin; kaempferol; apigenin) were analyzed, from which seventeen were partially or base line separated. The calibration curves were constructed in the interval 12-200 µg/mL with R2 values ranging from 0.9849 to 0.9992, using injection volume of 2 µL. The limit of detection (LOD) and limit of quantification (LOQ) per compound is determined, with values ranging from 5.5 µg/mL to 22.8 µg/mL and from 16.6 to 68.5 µg/mL, - respectively.

The species of Allium that were analyzed showed diverse compositions of polyphenols. From the seventeen polyphenols that could be analyzed using this method, only one, 3 4-dyhydroxybenzoic acid, was not found in any of the samples. Gallic acid is found in five out of six species, and for three of these samples the amount decreases as the concentration of added selenium increases. The most diverse composition of polyphenols is found to be in Allium cepa, with ten polyphenols in the control and sample treated with 1 mg/L selenium and eleven polyphenols in the one treated with 5 and 20 mg/L selenium solution. Generally, the samples treated with 20 mg/L selenium were the most affected ones, with lower amounts and number of polyphenols in their composition. For some samples like Allium cepa and Allium ampeloprasum the phenolic content increases when growing environment was enriched with 1 mg/L selenium, for other cases like Allium senescens the amount increases when 5 mg/L selenium added.
This research project gives an overview on how selenium influences the phenolic composition in Allium species. Allium cepa is the species that showed the most interesting results, showing a significant difference in total phenolic content, and the compositions of polyphenols. Nevertheless, more research has to be done to have a complete picture of the processes.