From the ethereal extract of Melilotus neapolitana Ten., an herbaceous plant living in the Mediterranean macchia, a new aromatic metabolite was isolated. The structure 1-(2,4-dihydroxyphenyl)2-(4-hydroxy-2-methoxyphenyl)1,3-propandiol, was elucidated on the basis of its mass spectrum and 1D and 2D NMR spectroscopic data (DQ-COSY, TOCSY, HSQC, HMBC). The relative configuration was determined from NOESY/ROESY experiments and computational calculations. The compound was tested for its potential allelopathic effect on two wild plant species living in the same habitat as M. neapolitana.