Unexpected Occurrence of Caffeine in Sleep-Inducing Herbal Teas

Abstract

Caffeine acts as a weak psychostimulant and is known to cause trouble with sleeping. Therefore, the presence of caffeine in sleep-aid herbal teas was somewhat surprising, and confirmatory investigations were conducted to exclude any possible misidentification. The botanicals of the sedative mixtures were analysed individually by ultra performance liquid chromatography (UPLC) coupled with a time-of-flight high-resolution mass spectrometer (TOF-HRMS), and caffeine was detected in linden (Tilia spp.) extracts. The presence of caffeine was unambiguously confirmed by means of its characteristic mass spectrum acquired during direct analyses of powdered linden by thermal desorption coupled to a GC×GC-TOF-MS. Caffeine content was determined in 11 linden-based samples, with a validated UPLC-MS/MS method using two mass transitions. Concentrations were between traces and 110 mg kg(-1) in the herbal material while those in the corresponding prepared sleep-inducing hot beverages ranged from traces to 226 μg per cup.

Do linden trees kill bees? Reviewing the causes of bee deaths on silver linden (Tilia tomentosa)

“…Intriguingly, Naef et al [41] reported caffeine (figure 1) in T. cordata nectar, and Mathon et al [72] detected caffeine in Tilia sp. flower tea.…”

“…Their effects on bumblebee foraging behaviour and persistence to return to empty flowers should furthermore be tested experimentally with artificial flowers. Intriguingly, Naef et al [41] reported caffeine (figure 1) in T. cordata nectar, and Mathon et al [72] detected caffeine in Tilia sp. flower tea.…”

For antagonists and mutualists: the paradox of insect toxic secondary metabolites in nectar and pollen

“…(Kretschmar and Baumann 1999), and Tilia spp. (Malvaceae) (Naef et al 2007;Mathona et al 2014). The flowers of these species are characterised by being small white and generally indistinct but with a strong aroma so these species may employ odour as the primary tool for attraction.…”

“…it may explain the phenomenon of dead bees under these trees-bees that overvalue the food source and continue to forage long after the tree has stopped producing nectar and ultimately run out of energy and drop to the ground and die since the nectar of Tilia spp. is reported to contain caffeine (Naef et al 2007;Mathona et al 2014).…”