Profiling of polyphenols in glandular trichomes of Mentha × piperita L. ‘Multimentha’

Abstract Mentha is an aromatic and medicinal plant which is widely used as food, medicinal spice, flavoring agent and in pharmaceutical industries. Beyond its characteristic sensory attributes, mint is cultivated predominantly for its essential oil, which is biosynthesized in specialized glandular structures called peltate trichomes. In addition to its aromatic properties, Mentha possesses a diverse range of non-volatile constituents, including phenolic acids and flavonoids, which significantly contribute to its pharmacological potential. Phenolic compounds were detected in extracts of whole leaves where they play a pivotal role in plant defense. Our histochemical assays indicated that peltate glandular trichomes contained polyphenols. The analysis by ultra-high-performance liquid chromatography coupled to mass spectrometry verified the presence of flavones, flavanones and phenolic acids in trichomes that were isolated by abrasion of the leaf surface with a cover glass combined with extraction of exudates that were liberated from the damaged glandular subcuticular space by shortly dipping the abraded leave into aqueous methanol (70%). This suggests that glandular trichomes are not only sites for the biosynthesis of secondary plant metabolites up to phenylpropenes, but also are capable of subsequent biosynthesis of rosmarinic acid and flavonoids.