Deciphering the interactions of genistein with β-cyclodextrin derivatives through experimental and microsecond timescale umbrella sampling simulations

Abstract

Genistein (GEN), an isoflavone, exhibits wide array of biological activities such as antioxidant, anti-inflammatory, cardioprotective and neuroprotective effects. However, despite of tremendous biological activities, its incorporation into functional foods and food supplements is limited due to its low aqueous solubility and instability. The present investigation unveils the molecular mechanism of inclusion of GEN inside the cyclodextrins (CDs) cavities with special emphasis on the correlation of experimental methods with molecular dynamics (MD) simulations. Herein, host – guest inclusion complexes (ICs) of GEN with two modified forms of β-cyclodextrins [Methyl-β-cyclodextrin (M-β-CD) & Hydroxypropyl-β-cyclodextrin (HP-β-CD)] were prepared using spray-drying to improve the aqueous solubility and the apparent stability of GEN. The ICs were characterized by fourier transform infra-red (FT-IR) spectroscopy, powder X-ray diffractometry (PXRD), scanning electron microscopy (SEM) and nuclear magnetic resonance spectroscopy (1H NMR and 2D-NOESY) providing appropriate evidences of the inclusion of GEN inside host cavities (CDs). The results of MD simulations demonstrated multiple conformations obtaining energy minimas of GEN/M-β-CD, whereas GEN/HP-β-CD only showed a single metastable structure. The results were further complemented by enhanced umbrella sampling simulations where GEN/M-β-CD demonstrated lower free energy of binding than GEN/HP-β-CD. Overall, this study presents basic mechanism behind GEN/CD inclusion complexes formation using experimental and computational approaches.