Isolation and characterization of isomeric tibetin spiroethers from the roots of Tanacetum dolichophyllum (Kitam.) Kitam

The roots of Tanacetum dolichophyllum (Kitam.) Kitam. (syn. Hippolytia dolichophylla (Kitam.) K.Bremer & Humphries) were collected from high altitude area of Munsyari, district Pithoragarh (Uttarakhand, India) yielded essential oil by steam distillation method and the oil was analysed by TLC and GC-MS. The GC-MS analysis of the essential oil sample showed the dominance of two constituents visible in sesquiterpene range. These constituents were isolated by column chromatography. The structures of these compounds were determined on the basis of ¹H-NMR,¹³C NMR, COSY, 135-DEPT, and HRMS (ESI-TOF) spectral data. The two major compounds were identified as isomeric C₁₄-Tibetin spiroethers, namely (E)-2-(2',4'-heptadiyn-1'-ylidene)-1,6-dioxaspiro[4.4]non-3-ene and (Z)-2-(2',4'-heptadiyn-1'-ylidene)-1,6-dioxaspiro[4.4]non-3-ene.