Bioassay-guided fractionation of a thymol-deprived hydrophilic thyme extract and its antispasmodic effect

Abstract Ethnopharmacological relevance Extracts from Thymus vulgaris L. and Thymus zygis L. are traditionally used for bronchitis, catarrhs of the respiratory tract and supportive treatment of pertussis. A potential spasmolytic effect is thought to be due to the presence of the monoterpenoid phenols thymol and carvacrol in the extract. Based on previous data the present investigation aimed to clarify if thymol-deprived thyme extracts (as been in use within German drug market) have antispasmodic activity. Additionally compounds responsible for this effect had to be identified. Materials and methods Thyme fluid extract was subsequently fractionated by FCPC, LPLC, and HPLC and compounds isolated were identified by spectroscopic methods. Bioassay testing was done by quantification of antispasmodic activity in the preconstricted rat smooth muscle trachea model against papaverin as positive control. Results Thymol-deprived spissum extract (SE) had good antispasmodic activity (−37%, related to the maximum contraction). Bioassay-guided fractionation indicated that rosmarinic acid and apigenin do not contribute to this effect. Luteolin contributed significantly to the antispasmodic activity (−9%). Conclusions Thyme extracts have antispasmodic activity, which is at least due to synergistic effects of phenolic volatile oil compounds and the flavone luteolin. Specifications of thyme-containing preparations should refer to this flavone in addition to focusing on the volatile phenols.