Isolation of chlorophylls from stinging nettle (Urtica dioica L.)

This study was aimed to assess the feasibility of extracting chlorophylls from stinging nettle (Urtica dioica L.) by solvent extraction. In preliminary, the investigation concerned three parts of raw material (leaves, stalk and whole plant), different preservation techniques (blanching and drying) and different storage temperatures of preserved material (−20 °C for blanched and 4 °C for dried sample). Extracts were analysed for chlorophyll A and chlorophyll B, respectively, by means of HPLC method. Afterwards, optimization of single-step conventional extraction was carried out by examining the influence of the following process parameters on the extraction yield and isolation efficiency of chlorophylls: type of organic solvent, content of water in ethanol/water mixtures, ratio solvent/material, temperature, time of extraction and pH of the extraction mixture. Furthermore, to improve the yield and/or the selectivity of the extraction, multi-step conventional extraction experiments as well as other solid–liquid extraction techniques (soxhlet and ultra-sound assisted) were performed and compared.