Metabolic Characterization of Four Members of the Genus Stachys L. (Lamiaceae)

Abstract

Several members of Stachys L. (among the largest Lamiaceae genera) have been traditionally used as medicinal plants. With 54 Stachys taxa (species and subspecies) occurring in mainland and/or insular Greece, the present study aimed to investigate the metabolic profiling of four range-restricted local Stachys members: Stachys candida and S. chrysantha (protected and endangered local Greek endemics), S. leucoglossa subsp. leucoglossa (local Balkan endemic), and S. spinulosa (local Balkan subendemic). In this investigation, the infusions of their above-ground parts were characterized using NMR and HPLC-PDA-MS techniques. Thus, 1D- and 2D-NMR spectra were obtained to compare the chemical fingerprints of these plants. Furthermore, previously isolated compounds from Stachys spp. were used to identify specific constituents. NMR screening revealed the presence of: (i) phenylethanoid glycosides, mainly acteoside in S. candida and S. chrysantha (section Candida, Swainsoniana phyloclade), and (ii) flavone 7-O-allosylglucoside (isoscutellarein 7-O-[6‴-O-acetyl-β-D-allopyranosyl]-(1→2)-β-D-glucopyranoside) and iridoids (monomelittoside or/and melittoside) in S. leucoglossa subsp. leucoglossa (section Olisia, Swainsoniana/Olisia phyloclade, Swainsoniana phyloclade) and caffeoylquinic acid (chlorogenic acid) in S. spinulosa (section Campanistrum, Stachys phyloclade). In total, 26 compounds were detected by HPLC-PDA-MS belonging to flavonoids, phenylethanoid glycosides, and phenolic acids. Among them, chlorogenic acid was identified in all samples as one of their main metabolites. The present study complements previous studies with first reports of constituents detected in the studied taxa, reports for the first time on the metabolic characterization of S. spinulosa, and discusses the chemotaxonomic significance of such findings.