The infusion of the semi-fresh flowering aerial parts of Sisymbrium officinale (L.) Scop. (Brassicaceae), commonly known as hierba del canto in Spanish, is a popular remedy for the treatment of sore throats, coughs, and hoarseness, but little is known about its chem. and pharmacol. HPLC-UV/PDA analyses of the dichloromethane and methanol exts. of both the fresh and the dried plant material showed the occurrence of some biochem. reactions during the drying process. The freeze-dried residue of the infusion (SOw) prepd. according to the traditional recipe, was re-dissolved in methanol obtaining a sol. fraction (SOw_s) and a ppt. (SOw_p). Further fractionation of SOw_s allowed the identification of adenine, adenosine, and guanosine that were present in significant quantities only in the traditionally prepd. aq. ext. Polysaccharides were detected in the SOw_p fraction and their mol. wt. evaluated by DOSY expts. When they all were tested for the topical anti-inflammatory activity in the murine Croton oil-induced ear edema model, only a modest effect was obsd. at high concns. Satn. Transfer Difference-NMR expts. for the study of the binding activity between the plant metabolites and the Lens culinaris lectin gave partial data on the active principles. This work affords new data on the phytochem. of the plant but the question about the identity of the active principles responsible for the traditional use of S. officinale remains open.