Potential bioactive phenolics of Macedonian Sideritis species used for medicinal “Mountain Tea”

Abstract

Twenty four phenolic compounds have been characterised in medicinal Sideritis species (aerial parts) from Macedonia by liquid chromatography–UV diode array coupled to ion-trap mass spectrometry with electrospray ionisation interface (negative mode). Three new phenylethanoid glycosides, alyssonoside, echinacoside, and forsythoside were detected for the first time in the genus of Sideritis, along with two known phenylethanoid glycoside verbascoside and leucoseptoside A. Three hydroxycinnamic acids, such as, 3-caffeoylquinic acid, 5-caffeoylquinic acid and feruloylquinic acid, five flavonoid 7- O-diglycosides of apigenin, hypolaetin, 3′- O-methylhypolaetin, isoscutellarein and 4′- O-methylisoscutellarein and 11 acetylated flavonoid 7- O-diglycosides. The phenolic profile of different parts of two wild and cultivated grown Sideritis species from Macedonia has been analysed using water and methanol extracts to give an insight of the nature of the flavonoids in their glycosylated forms and combinations with phenolic acids present in the plants. The structures of flavonoid glycosides were analysed before and after alkaline hydrolysis. The effect of sugar substitution and acetylation on the flavonoids and ESI ionisation and fragmentation are discussed.