Occurrence of tropane alkaloids, pyrrolizidine alkaloids and mycotoxins in rooibos: a comprehensive safety assessment.

Abstract

Rooibos is a naturally caffeine-free herbal tea, widely consumed in Europe and perceived as a safe drink. However, contamination by natural toxins can pose a potential food safety concern for regular consumers. This study investigated the presence of 32 pyrrolizidine alkaloids (PAs), 16 tropane alkaloids (TAs), and 56 mycotoxins in 203 rooibos samples purchased from 18 European countries, using UHPLC-MS/MS. PAs were detected in 98% of the samples and were dominated by Senecio-type alkaloids, particularly senecionine N-oxide, senecionine, and retrorsine N-oxide. The mean and median total PA concentrations were 47 and 33 μg/kg, respectively, and all 2024 samples were below the EU maximum level of 400 μg/kg. TAs were rarely detected, with atropine present in only two samples and at low concentrations. Mycotoxin analysis revealed widespread contamination by Alternaria toxins, especially tenuazonic acid, detected in all samples, followed by alternariol monomethyl ether, alternariol, and tentoxin. Transfer experiments showed significant migration of PAs and Alternaria toxins into infusions. Preliminary exposure estimates have suggested a limited risk at mean contamination levels, although highly contaminated samples may contribute significantly to cumulative exposure to PAs. A comparison of results obtained between 2020 and 2026 suggested lower median PA contamination after implementation of the EU limit, despite sporadic exceedances.