Study of the isoflavone content of different extracts of Medicago spp. as potential active ingredient

• Different extracts from seven species of Medicago were obtained.
• Genistin, daidzein and genistein were the main isoflavones in extracts.
• The total isoflavones content is higher in M. rigidula and lower in M. sativa.
• Alcoholic solvent is the best, however, hydro-alcoholic solvent has promising results.
• This was the first study demonstrating isoflavones profiles in extracts of these Medicago species.

This study focuses on the isoflavones composition of different extracts of Medicago species (M. minima, M. tornata, M. truncatula, M. rigidula, M. scutelata, M. segitalis and M. sativa), a leguminous crop used as animal feeding. There are some research studies on the isoflavones composition of Medicago sativa, but no comprehensive profile of isoflavones has been reported for these other six species. In this work, two glycosides (daidzin and genistin) and six aglycones (daidzein, glycitein, genistein, formononetin, prunetin and biochanin A) were determined by high performance liquid chromatography (HPLC/DAD) in three different extracts of these species: aqueous, hydroalcoholic and alcoholic. In all samples genistin, daidzein and genistein were the most abundant isoflavone compounds. The highest concentration of genistin was observed in the extracts of M. scutelata (5.2 and 9.6 mg/kg db, respectively, for hydroalcoholic and alcoholic extract), in amounts 2–4.5-fold higher than the other samples evaluated. Daidzein is also present in high amounts in M. scutelata (19.2 mg/kg db, alcoholic extract). Genistein is detected in several species at concentrations ranging from 0.7 (aqueous extract of M. tornata) to 16.1 mg/kg db (alcoholic extract of M. scutelata). In terms of total isoflavones content per species, results showed significant differences between M. rigidula and M. sativa, considering all type of solvents, being the highest and the lowest one, respectively. In a general way, the extractability of compounds significantly increased from aqueous to alcoholic extracts. The study demonstrates that some Medicago species possess an excellent potential as a source of these health promoting bioactive compounds.