Nanoencapsulation of pharmaceutically active natural compounds into porous systems through sol-gel method leads to new drug delivery materials with sustained release behaviour of the entrapped pharmaceuticals. Properties of inorganic sol-gel-derived silica microparticles loaded with cotton (Gossypium hirsutum) seeds extract are reported. Xerogels obtained by heat or freeze drying were investigated by X-ray diffraction, dynamic light scattering, differential thermal analysis (DTA)/thermogravimetric analysis (TGA), UV-Vis and fluorescence spectroscopy. Effects of drying process on both silica particles and plant extract were evaluated. In vitro release was studied in release media with pH 1.1 and 7.4. The investigated biocomposite systems display a biphasic release profile wherein the diffusion prevails over the dissolution. Graphical Abstract