Acylated iridoid glycosides from the flowers of Verbascum lasianthum Boiss. ex Bentham

Verbascum, commonly known as “Mullein“, is represented by 228 species in the flora of Turkey [1]. During our field expeditions on Turkish folk medicine, we have recorded that the flowers of Verbascum lasianthum Boiss. ex Bentham are used for hemorrhoids in southwest Anatolia [2]. Verbascum species have been known to be rich in iridoid glycosides. Verbascum is well known for its variety of iridoids being of value for taxonomic evaluation of this genus. In previous studies, we described the isolation of nine iridoid glycosides and two phenylethanoid glycosides from the roots of V. lasianthum [3, 4]. In a continuation of the studies on Verbascum lasianthum, chromatographic studies (VLC, HPLC and CC) on the water soluble parts of the methanolic extract resulted in the isolation two new iridoid glycosides, 6-O-(4'''-O-trans-p-coumaroyl)-α-L-rhamnopyranosylaucubin (1), 6-O-(4'''-O-trans-p-methoxycinnamoyl)-α-L-rhamnopyranosylaucubin (2), and five known iridoid glycosides, sinuatol (3), aucubin (4), geniposidic acid (5), catalpol (6), ajugol (7) as well as a known saponin, ilwensisaponin A (8) from the flowers of Verbascum lasianthum. Their structures were determined by spectroscopic methods (UV, IR, 1D, 2D NMR and MS).

1: R=H; 2: R=CH₃

References: 1. Huber-Morath, A. in P. H. Davis (ed) (1978), Flora of Turkey and the East Aegean Islands, University Press, Edinburgh, Vol. 6, pp. 461–603. 2. Tuzlaci, E., Erol, M.K. (1999), Fitoterapia 70: 593–610. 3. Akdemir, Z.S. et al. (2004) Turk. J. Chem. 28: 101–110. 4. Akdemir, Z.S. et al. (2004) Turk. J. Chem. 28: 227–234.