A rapid and highly specific method to evaluate the presence of pyrrolizidine alkaloids in Borago officinalis seed oil

摘要

Pyrrolizidine alkaloids (PAs) are complex molecules, present in plants as free bases and N-oxides. They are known for their hepatotoxicity, and consequently there is a health risk associated with the use of medicinal herbs that contain PAs. Unfortunately, there is no international regulation of PAs in foods, unlike those for herbs and medicines: in particular, for herbal preparation or herbal extracts, the total PA content must not exceed 1 μg/kg or 1 μg/l, respectively. Borago officinalis seed oil is a source of γ-linolenic acid, and its use is increased in both pharmaceutical and health food industries. Even if studies based on gas chromatography and TLC methods showed that PAs are not co-extracted with oil, the development of a rapid and sensitive method able to evaluate the presence of PAs in commercially available products is surely of interest. The presence of PAs in a commercially available Borago officinalis seed oil was tested either in the oil sample diluted with tetrahydrofuran/methanol (MeOH)/H_2O (85/10/5 v:v:v) or after extraction with MeOH/H_2O (50/50 v:v) solution The samples were analysed by electrospray ionization in positive ion mode and in high mass resolution (60 000) conditions. In both cases to evaluate the effectiveness of the method, spiking experiments were performed adding known amount of two PA standards to the borage seed oil. A limit of detection in the order of 200 ppt was determined for these two compounds, strongly analogous to Borago officinalis seed oil PAs. Consequently, if present, PAs level in Borago officinalis seed oil must lower than 200 ppt.