Quantitative Analysis of Isoflavones from Fabaceae Species and Their Chemopreventive Potential on Breast Cancer Cells

The <i>Fabaceae</i> family is known for the presence of isoflavones-phytoestrogens with potential chemopreventive effects against hormone-dependent cancers. This study aimed to optimize isoflavones extraction using a fractional factorial design and to quantitatively and qualitatively analyze 32 <i>Fabaceae</i> species native to Polish flora by HPLC-UV-VIS to indicate new, rich plant sources of isoflavones. The optimal extraction method was a 60 min reflux with 50% methanol and a plant material-to-solvent ratio of 1:125. The highest isoflavone levels were found in <i>Trifolium medium</i> (26.70 mg/g d.m.), <i>Genista tinctoria</i> (19.65 mg/g d.m.), and <i>Trifolium pratense</i> (12.56 mg/g d.m.). The obtained extracts were further evaluated for cytotoxic and antiproliferative activity against MCF7 and MDA-MB-231 human breast cancer cells. <i>Genista tinctoria</i> showed the highest cytotoxicity against MCF7, while <i>Cytisus scoparius</i> and <i>Ononis arvensis</i> were most effective against MDA-MB-231 at a dose of 500 µg/mL. The extracts were also characterized by varied, potent antioxidant properties, important in chemoprevention. A strong correlation was observed between isoflavone content and cytotoxic and antiproliferative activity exclusively in the estrogen receptor-positive MCF7 cell line. Importantly, the tested extracts demonstrated no toxic effects on normal human liver (HepG2), thyroid (Nthy-ori 3-1), or breast (MCF10A) cells, indicating a favorable safety profile.