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Revisiting the caffeine-free status of rooibos and honeybush herbal teas using specific MRM and high resolution LC-MS methods

Stander, Maria A., Joubert, Elizabeth, De Beer, Dalene
Subtropical plant science 2019 v.76 pp. 39-43
Aspalathus linearis, Cyclopia genistoides, Cyclopia intermedia, Cyclopia subternata, caffeine, detection limit, herbal tea, ions, liquid chromatography, mass spectrometry, reference standards
Two endemic South African herbal teas, namely rooibos (Aspalathus linearis) and honeybush (Cyclopia spp.), are especially valued for their caffeine-free status. No recent evidence based on state-of-the-art analytical methodology with low limits of detection (e.g. below 1 μg/L) is available. The current study provides such evidence. Randomly selected samples of fermented rooibos (n = 10) and honeybush herbal teas from four species (n = 10 each), namely C. intermedia, C. subternata, C. genistoides and C. longifolia, were analysed and no caffeine detected. Similarly, no caffeine was detected in green rooibos and C. genistoides herbal teas (n = 10 each) indicating that it is absent in the plant. Method specificity was shown to be important since peaks with molecular ion [M+H]+ and product ions resembling those of caffeine were detected, although the retention time and accurate mass did not match those of an authentic reference standard for caffeine.