Bioassay-guided isolation of anti-inflammatory and antinociceptive glycoterpenoids from the flowers of Verbascum lasianthum Boiss. ex Bentham

Abstract

Infusions of Verbascum lasianthum flowers have been used for hemorrhoids in Turkish folk medicine. In order to evaluate the scientific basis for this practice, in vivo anti-inflammatory and antinociceptive activities of Verbascum lasianthum Boiss. ex Bentham flowers were investigated. A methanolic extract of the flowers was shown to possess significant inhibitory activity in the carrageenan-induced hind paw edema model and in p-benzoquinone-induced writhings in mice. Through bioassay-guided fractionation and isolation procedures eight compounds, 6- O-(4‴- O- trans- p-coumaroyl)-α- l-rhamnopyranosylaucubin ( 1), 6- O-(4‴- O- trans- p-methoxycinnamoyl)-α- l-rhamnopyranosylaucubin ( 2), sinuatol ( 3), aucubin ( 4), geniposidic acid ( 5), catalpol ( 6), ajugol ( 7) and ilwensisaponin A ( 8) were isolated and their structures were elucidated by spectral techniques. An iridoid glucoside, aucubin ( 4) and a triterpenoid saponin, ilwensisaponin A ( 8) were found to possess significant antinociceptive and anti-inflammatory activities, per os without inducing any apparent acute toxicity or gastric damage. Results of the present study support the continued and expanded utilization of plants employed in Turkish folk medicine.