Antioxidant and cholinesterases inhibitory activities of Verbascum xanthophoeniceum Griseb. and its phenylethanoid glycosides

The members of Verbascum L. (Scrophulariaceae) are known to be rich in phenylethnoid glycosides, and among them Verbascum xanthophoeniceum is an endemic plant species for the Balkan region, Northwestern, and Southern Turkey. A scheme was developed for the isolation of the main active constituents that accumulate in plant aerial parts. The antioxidant activities of total methanol extracts, collected phenylethanoid glycosides fractions and specific active constituents (forsythoside B, verbascoside and leucosceptoside B) were then evaluated in 2,2′-diphenyl-1-picrylhydrazyl (DPPH·), oxygen radical absorbance capacity (ORACFL), hydroxyl radical averting capacity (HORACFL), ferric-reducing antioxidant power (FRAP), and superoxide anion ( O 2 - ) radical scavenging assays. In vitro acetylcholinesterase (AChE) and butyrylcholinesterase (BChe) inhibitory activities of abovementioned extracts, fractions and isolated pure compounds were also examined. Depending on the method used, forsythoside B, verbascoside and leucosceptoside B proved to be effective radical scavengers and cholinesterases inhibitors. On the basis of these findings it can be proposed that in addition to providing a potent source of antimicrobial and anti-inflammatory compounds, Verbascum plants could serve as attractive mines of powerful antioxidants for various purposes.