Abstract
► DART plus HRMS is required to detect the neurotoxin anisatin in star anise fruits and teas. ► No sample clean-up is required, the method is fast (seconds) and simple. ► Japanese star anise can be unambiguously distinguished from Chinese star anise. ► Semi-quantitative results can be obtained by standard addition.
After ingestion, products containing Chinese star anise (Illicium verum) contaminated or adulterated with Japanese star anise (Illicium anisatum) or other Illicium species, can cause epilepsy, hallucinations, and nausea due to the rare neurotoxic sesquiterpene dilactone anisatin that is present in Japanese star anise. Thus a rapid, simple and unambiguous method for distinguishing between the morphologically similar Chinese star anise and toxic Japanese star anise is important for food safety issues. Direct Analysis in Real Time (DART) ambient ionisation coupled with orbitrap high resolution mass spectrometry allowed the recording of mass spectra of anisatin in solid star anise fruits in seconds without any prior sample pretreatment. Spectra could be obtained in both positive ([M+NH4]+ at m/z 346.1496, C15H24NO8) and negative mode ([M−H]− at m/z 327.1074, C15H19O8) and gave the same outcome provided a mass resolution of at least 27,000 is available. The anisatin signal was typically >1000 times larger in Japanese star anise than in Chinese star anise thus allowing an unequivocal qualitative determination. Herbal teas containing star anise fragments too small to be visually recognised, could be analysed by preparing a tea in 6min and subsequently sampling ∼2μL of tea on a glass rod. None of the 8 investigated retail teas contained significant quantities of anisatin. Spiking a complex herbal tea containing Chinese star anise with an equally concentrated tea prepared from Japanese star anise provided a linear calibration curve (R2≥0.995) after normalising on a native constituent of Chinese star anise (standard addition method). This showed that adulteration down to 1% (w/w) is still measurable. Compared with existing PCR, TLC, GC–MS and HPLC–ESI-MS/MS procedures, the proposed DART–HRMS procedure is faster and simpler and moreover measures the actual biotoxin.