Optimization of extraction of pyrrolizidine alkaloids from plant material

Various techniques of extraction of pyrrolizidine alkaloids (PAs) from comfrey have been developed and compared. Different extraction media: methanol, ethanol, 1% methanolic solution of tartaric acid, 2.5% HCl solution, 5% CH 3 COOH solution, alkaline chloroform-methanol mixture at various temperatures (room temperature, 50-60°C, solvent's boiling point) have been used in various extraction techniques (percolation, electric basket, ultrasonic water bath) and various extraction times. Total concentration of pyrrolizidine alkaloids (PAs) was estimated from UV-VIS spectrophotometric studies according to Dann--Mattocks procedure. For the most promising extraction techniques one determined recoveries of monocrotaline added to crude pre-extracts. Extraction and co-extraction processes were investigated using UV-VIS spectra of the adducts of3,4-dehydro-PAs and Ehrlich's reagent. The best result of PAs extraction from comfrey was obtained using 1% methanolic solution of tartaric acid and electric basket technique at the temperature 100 ± 5°C for 2 h. Possible applications of the method have been discussed.