Exhausted roots of licorice: an unexplored potential source of bioactive compounds

Licorice, the dried roots of Glycyrrhiza species (Fabaceae family) is one of the oldest and most widely used herbal drugs in both eastern and western countries. Due to its sweet taste, it is also used in the preparation of candies and as a fl avoring additive in food and tobacco industries. Numerous authors have reported that the chemical constituents of licorice have biological effects such as anti-infl ammatory, anti-ulcer, anti-hepatotoxic, anti-microbial, anti-viral and anti-oxidant benefi ts. The traditional and industrial productions of candies mainly use hot water or steam distillation in order to produce licorice extract. The result of this process is an aqueous extract and a solid residue consisting of exhausted licorice roots. This residue is normally used as soil conditioner in local agricultural activities; some alternative uses have been proposed, like the production of activated carbon, but nothing concerning the extraction of bioactive compounds. In order to characterize the chemical composition of the exhausted licorice roots, a metabolomic approach has been used that has proven to be a fast, reliable and highly effi cient method for the simultaneous determination of a high number of compounds. High Performance Liquid Chromatography - High Resolution Mass Spectrometry (HPLC-HRMS) measurements, combined with statistical methods, revealed the metabolites composition of the licorice residues. Many of the identified compounds in this matrix are known for their effects on human health, like glycyrrhizin, the main – and the most studied - constituent of licorice roots. Two different extraction solvents were tested and the relevant extracts were analyzed to elucidate the composition differences and the extraction effi ciency. The dried extracts were also tested for biological activity. Preliminary results show a moderate bioactivity for the methanol/water extracts on some staphylococcus aureus strains. This is the fi rst report concerning possible alternative uses of this kind of material and we believe that the residues analyzed in this work can be characterized as raw material for the extraction of some chemical compounds with pharmacological activity