Content of selected biologically active compounds in tea infusions of widely used European medicinal plants

Herbal tea infusions are a very important source of flavonoids and other biologically active compounds in human medicine and nutrition. Melissa officinalis, Agrimonia eupatoria, Sambucus nigra, Achillea millefolium, Filipendula ulmaria, Betula pendula and Glechoma hederacea were selected as common European medicinal herbs and sources for tea infusion preparations. Quercetin, rutin, catechin, chlorogenic acid, and squalene were determined in the prepared infusions. Free quercetin was not found in any of the infusions, but tea infusions did contain rutin and other quercetin glycosides, the content of which was, after acid hydrolysis, determined as quercetin. The highest levels of total quercetin were found in infusions from Filipendula ulmaria and Sambucus nigra (120 and 108 mg L-1, respectively) corresponding to the content of rutin found also in these two infusions (25.2 and 194 mg L-1, respectively). The Sambucus nigra infusion contained the largest content of chlorogenic acid (166 mg L-1), and infusions from Melissa officinalis, Agrimonia eupatoria, Betula pendula and Glechoma hederacea contained only small amounts of squalene.