Synthesis, characterization, and cytotoxic activity of fructose-metal borate esters

Calcium fructoborate (CaFB) is one of the most promising organic complexes in boron chemistry due to its chemical stability and biological activity. The toxicological safety, high bioavailability, and multiple mechanisms of action of organic boron compounds render CaFB not only a nutritional supplement but also a metabolic regulatory agent. Although boron is a necessary micronutrient for plant metabolism, its biochemical role in human physiology has remained controversial for many years. Current research, however, clearly demonstrates that boron is not merely a trace element but also a bioactive compound effective in regulating metabolic processes. Beyond its antioxidant and anti-inflammatory properties, its effects on cellular energy metabolism, mineral balance, and hormone regulation are also becoming increasingly well understood. In this study, the synthesis of CaFB was reproduced based on patented methods described in the literature, and fructoborate esters with different metal ions (Na, Mg, Ca) were synthesized. The structural characterization of the synthesized compounds, obtained by crystallization or precipitation from aqueous solutions in the solid state, was carried out using elemental analysis, melting point determination, infrared spectroscopy (FT-IR), thermal analysis (TGA/DTA), and mass spectrometry (GC-MS). Furthermore, the cytotoxic activities of these compounds were evaluated in MCF-7 (breast cancer) and MCF-12A (normal breast epithelial) cell lines using the MTT assay. Among the tested compounds, CaBF-mono and CaBF-di exhibited the highest cytotoxic activity against MCF-7 cells, with IC₅₀ values of 8.488 and 8.614 µg/mL, respectively, whereas NaBF-di showed moderate activity (IC₅₀ = 31.500 µg/mL), and MgBF-mono exhibited no significant cytotoxic activity (IC₅₀ > 100 µg/mL). In contrast, the synthesized compounds exhibited relatively low cytotoxicity against normal MCF-12A cells, demonstrating a selective activity profile against cancer cells. These preliminary findings indicate that fructose-boron ester compounds represent a promising group of candidates warranting further investigation in terms of their cytotoxic and selective activity profiles.