Pyrone derivatives from Helichrysum italicum.

Chemical investigation of aerial parts of Helichrysum italicum yielded two new pyrone derivatives (1 and 2) along with ten known compounds. The structures of the new compounds were established by 1D and 2D NMR spectra as well as by HRESIMS data. Compound 1 represented a rare dimer of substituted α- and γ-pyrone units. DFT-NMR and TDDFT-ECD calculations were carried out to determine the absolute configuration of 1 but failed, representing the limitation of TDDFT-ECD calculation for the configurational assignment. All compounds were measured for their antibacterial and cytotoxic activity but proved to be inactive.