Pyrrolizidine alkaloids in Tussilago farfara from Bulgaria

Abstract

Tussilago farfara L. (Asteraceae) is widespread in Bulgaria and commonly known as ‘podbel.’ Although T. farfara is a common and widely used herb in folk medicine in the past and today, a study of alkaloid content from Bulgarian populations, which is the aim of this study, has not been done yet. Conventional processing of the dried and powdered plant material (Farfarae folium) including a mild reduction with Zn/HCl of the methanol extracts to convert N-oxides to tertiary bases resulted in the preparation of crude alkaloid mixture (CAM) of pyrrolizidine alkaloids (PAs). The alkaloids were identified by gas chromatography–mass spectrometry analysis of the CAM. A total of four PAs were detected in Farfarae folium herbal substance. Senkirkine and senecionine were found to be major alkaloids, together with integerrimine and seneciphylline, as minor components. The alkaloid content was relatively low (0.0055%) or 55 µg/g. All of the above-mentioned alkaloids were unsaturated at 1,2 position and belonged to the group of the highly hepatotoxic macrocyclic diesters. The content of PAs has to be controlled in processes of T. farfara herbal gathering and herb production, quality control of food, nutrient supplements and other coltsfoot based products. The good botanical identification of T. farfara and morphologically closer PA content species is a prerequisite for quality monitoring and control of plant based products. Microscopic differentiation of the leaves of coltsfoot and butterbur (Petasites spp.) was established and described.