Research on dehydrogenation of gomphrenin in heated ammonia solutions of organic solvents

In this report, the influence of ammonia on dehydrogenation of gomphrenin pigment, isolated from purple inflorescences of Gomphrena globosa L., in selected organic solvents (methanol, ethanol, acetone and acetonitrile) at 40°C is presented. Betacyanins are water-soluble, vacuolar plant pigments. Due to their numerous pro-health properties, they can be applied in the pharmaceutical industry and as food colorants. However, as most of natural products, they are less stable than synthetic dyes, therefore, further studies need to be carried out on their stability, but also on determination of their degradation products as well as degradation mechanisms. For the experiments of the ammonia treatment, prolonged isolation of gomphrenin from the plant material including extraction, preliminary purification, preparative HPLC fractionation, concentration and liofilization were performed. The tested pigment dissolved in organic solvents was treated by ammonia and the samples for analysis were taken during and after reaction. For identification of obtained derivatives of gomphrenin, high-performance liquid chromatography with diode-array and mass spectrometric detection (LC-DAD-ESI-MS) was performed. As a result of heat processing, the mixture of decarboxylated and dehydrogenated gomphrenin derivatives was detected. Based on the experimental results, it can be stated that gomphrenin is characterized by the greatest stability in methanolic solutions while it is the most labile in the acetonitrilic ones.