Plantago L. species aqueous extracts: Chemical characterization and in vitro biological activity of plantains leaf teas

Abstract

Genus Plantago L. belongs to the group of traditionally used medicinal plants, recognized and accepted by modern medicine. The aim of this study was to analyze and valorise functional potential of water extracts (teas) prepared from six Plantago species: P. altissima L., P. argentea Chaix, P. holosteum Scop., P. lanceolata L., P. major L. and P. media L. Detailed chemical characterization of plantains teas was performed by spectrophotometry, HPLC-MS/MS and HPLC-DAD methods. Samples’ potential to inhibit α-amylase and tyrosinase, was evaluated by in vitro assays, while anti-inflammatory activity assessment was done by using U937 monocytes as in vitro model system, considering modulatory effect on production of metabolites of cyclooxygenase (COX) pathway of arachidonic acid metabolism: prostaglandin E₂ (PGE₂) and thromboxane A₂ (TXA₂). Dominant compounds in plantains teas were iridoids aucubin (97.4 mg per cup of a tea (tc) of P. media) and catalpol (53.2 mg/tc, P. altissima), and phenylethanoids acteoside (406 mg/tc, P. media) and plantamajoside (70.3 mg/tc, P. major). Most abundant flavonoids were luteolin and luteolin-7-O-glucoside, while chlorogenic and vanillic acid were dominant phenolic acids. P. media tea exhibited the highest α-amylase inhibition capacity, while P. holosteum, P. argentea, and P. altissima teas demonstrated the strongest inhibitory activity against tyrosinase. To the best of our knowledge, this is the first study investigating these bioactivities of the aforementioned plant species. Five Plantago teas reduced PGE₂ production (from 15.8 % to 28.1 %), while four samples reduced TXA₂ production (from 16 % to 28.2 %). P. altissima tea reduced COX-2 mRNA expression by 9.1 folds. In general, Plantago teas demonstrated remarkable in vitro biological activity, with P. media standing out for its broad range of potential curative properties based on the applied in vitro assays. Furthermore, this is one of the first studies to reveal the comprehensive chemical composition of Plantago teas. The findings provide significant insights into the bioactivity of poorly investigated species, highlighting the need for further research on these plants, which may have applications in the food, cosmetic, and pharmaceutical industries.