Senecio angustifolius as the major source of pyrrolizidine alkaloid contamination of rooibos tea (Aspalathus linearis)

Abstract

Pyrrolizidine alkaloids (PAs) and their N-oxides (PANOs) were detected in commercial rooibos tea which resulted in an investigation into the source of the contamination. Field studies showed that Senecio angustifolius occurs as a common weed throughout the production area and that it contains high levels of the same PAs (and in the same ratios) as those found in contaminated rooibos tea. The weed superficially resembles rooibos tea plants and is easily overlooked during weeding and harvesting. Analysis of a large number of plant material samples, collected from plantations from seven regions in the production area, showed that the rooibos plant (Aspalathus linearis) does not produce PAs. The detection of PAs in some rooibos plant materials from fields heavily infested with Senecio angustifolia can be explained by the recently demonstrated process of lateral transfer of PAs.