Chemical Constituents from the Aerial Parts of Onosma Erecta (Boraginaceae)

Onosma erecta is a Greek endemic plant belonging of Boraginaceae family. The methanolic extract of its aerial parts afforded after chromatographic separations simple hydroxylated compounds such as cis-3-(hydroxymethoxy)propenoic acid, 4-methyl-2-hydroxypentanone, both appearing for the first time as natural products, as well as tricarballylic acid along with the N-oxides of four pyrrolizidine alkaloids (PAs) (1–4). Structures 1, 3 and 4 reported in the present work as well as their free bases after reduction, are new natural products, while structure 2 has been determined before [1]. The chemical structures of all compounds have been determined by means of 1D and 2D NMR spectroscopy and ESI-MS.