HPLC-Ms characterization of phenylpropanoid glycosides from Aloysia polystachya (Griseb. et Moldenke)

Aloysia polystachya (Griseb. et Moldenke) is a herbaceous aromatic plant of the Verbenaceae family, widely distributed in subtropical regions of South America, mainly Paraguay and the north of Argentina, commonly known as “burrito” or “té-burro” (Botta, 1979). The leaves are prepared as an aqueous infusion or decoction, commonly used as dietary supplement or a tea substitute in daily life, as a remedy to treat all kind of gastrointestinal disorders, such as spasm or indigestion, pain, nausea, vomiting, dyspepsia and gastritis (Martìnez Crovetto, 1981; Martìnez & Pochettino, 1992; Filipov, 1994; Alonso & Desmarchelier, 2005). The leaves of Aloysia spp., among phenolic compounds, such as flavonoids, and phenolic acids, contain also phenylpropanoid glycosides, water-soluble compounds widely distributed, most of them deriving from medicinal herbs. Among them, verbascoside is the most abundant one in Aloysia spp.. To our knowledge, data on the chemical characterization of Aloysia polystachya (Griseb. et Moldenke) are poor in the literature, and, in particular, no study on the phenylpropanoid glycosides has been performed to date. In this work, HPLC-MS qualitative determination of the phenylpropanoid glycosides fraction, purified by Solid Phase Extraction (SPE), in Aloysia polystachya (Griseb. et Moldenke) extract was performed. Two different MS techniques have been coupled to HPLC: ion trap tandem-mass spectrometry (IT-MS), and the quadrupole-time of flight-mass spectrometry (Q-TOF-MS). The LC-IT-MS analyses were employed to support tentative structure identification, on the basis of m/z values of detected ions. The LC-Q-TOF-MS analysis enabled to calculate the accurate mass measurements, provided the most probable molecular formula, and is useful to identify the compounds present in the extract. Nine phenylpropanoid glycosides were identified in methanolic extract of the Aloysia polystachya (Griseb. et Moldenke) leaves. Among them, the compounds forsythoside A, plantainoside C, purpureaside D, martynoside and its two isomers were identified here for the first time. The results present here could be helpful in the future developing and validating of an analytical method to quantify the isolated compounds, and to assess the quality of Aloysia polystachya (Griseb. et Moldenke) leaves. Knowledge of the content of phenylpropanoid glycosides could further contribute to the chemotaxonomy of the genus.