Sideritis clandestina (Bory & Chaub.) Hayek subsp. peloponnesiaca (Boiss. & Heldr.) Baden (SCP) is endemic to the mountains of the Northern Peloponnese (Greece). This and other Sideritis taxa, collectively known as mountain tea, are widely ingested as beverages for refreshment or medicinal purposes. We describe a methodology for the characterization of SCP. Four iridoid glycosides (monomelittoside, melittoside, ajugoside, and 7-O-acetyl-8-epiloganic acid), two phenolic acid glycosides (vanillic and salicylic acid glycosides), and three caffeoyl ester glycosides (chlorogenic acid, verbascoside, and isoverbascoside) were isolated from SCP for the first time. We used ultrasound-assisted extraction of 3 g of plant material to produce petroleum ether and aqueous extracts, which we then analyzed using GC/MS and LC/MS. This was applied to eight samples from four different taxa. In total, 70 volatile and 27 polar metabolites were determined. The S. clandestina samples had a lower phenolic content and weaker antioxidant properties than S. raeseri and S. scardica. However, S. clandestina ssp. clandestina seemed to be the most aromatic taxon, with almost double the number of volatiles as the others. Τhis study could contribute to authentication and chemotaxonomic studies of Sideritis taxa.
Keywords: Lamiaceae; ajugoside; flavonoids; iridoids; melittoside; metabolomics; mountain tea; phenylethanoids; ultrasound-assisted extraction; verbascoside.