Phenolic Compounds and Iridoids of the Aerial Part of Leonurus deminutus V. I. Krecz. (Lamiaceae)

Abstract

Objective: The genus Leonurus L. comprises seven Siberian species, among which Leonurus deminutus V. I. Krecz. is widespread in Irkutsk oblast. This plant is used in folk medicine in the form of infusions, tinctures, and juices for treatment of anxiety disorders, irritability, insomnia, and hypertension and is a promising agent for introduction into pharmaceutical practice. In this regard, the aim of this study was to investigate the composition and content of the main biologically active substances (flavonoids, phenylpropanoids, and iridoids) of the aerial part of L. deminutus. Methods: HPLC-DAD-ESI-MS method was used for the analysis. The quantitative determination of the revealed phenolic compounds was carried out by the MC-HPLC-UV method. The iridoid profiling analysis of the aerial parts of L. deminutus was performed using the HPLC-DAD-ESI-MS method. Results and Discussion: The study revealed the presence of 20 phenolic compounds in the aerial organs of L. deminutus, of which 11 substances were isolated and identified for the first time: 4-O-caffeoylquinic acid, 5-O-caffeoylquinic acid, caffeoylmalic acid (isomer 9), rutin, nicotiflorin, isoquercitrin, leonosides A and B, astragalin, apigenin 5-O-glucoside, and genkwanin 5-O-glucoside. Conclusions: It was found that the aerial part of L. deminutus contained 13.76 mg/g total flavonoids and 75.4 mg/g total phenylpropanoids. The following iridoids were for the first time detected and identified in the aerial parts of L. deminutus: harpagide, ajugol isomer, 8-acetylharpagide, and ajugoside. According to the literature, these substances are characteristic of other representatives of the genus Leonurus L., as confirmed by the present study via comparative analysis of the alcoholic extracts of L. deminutus and L. cardiaca by TLC.