Recycling of Almond By-Products for Intestinal Inflammation: Improvement of Physical-Chemical, Technological and Biological Characteristics of a Dried Almond Skins Extract

Background: Almond skins are rich in bioactive compounds that undergo oxidation/degradation phenomena and are poorly soluble in water, reducing in vivo absorption and bioavailability, factors that influence the pharmacological activity of an active product. We developed a dried acetonic almond skins extract/cyclodextrin complex to improve extract solubility, dissolution rate and biological activity. Methods: A lyophilized acetonic almond skin extract was produced. To optimize complex formulation, phase solubility studies and complex characterization (absorption studies, differential scanning calorimetry (DSC), morphology, solubility studies) were performed. To evaluate a possible use in healthy products, tumor necrosis factor-α levels and reactive oxygen species release, as well as cicloxygenase-2 and inducible nitric oxide synthase expression in intestinal epithelial cells, were also evaluated. Results: Phase solubility studies showed a Bs-type profile. A 1:1 dried acetonic almond skins extract/cyclodextrin ratio was able to improve extract water solubility and dissolution rate (100% in 45 min). The UV-Vis spectra of complex revealed a hypsochromic and hyperchromic effect, probably due to a partial inclusion of extract in cyclodextrin cavity through weak bonds, confirmed by DSC and morphology studies. The technological improvement in the extract characteristics also led to better biological activity. In fact, the complex effectively reduces tumor necrosis factor-α levels with respect to the pure extract and significantly inhibits the reactive oxygen species release, even if only at the lower concentration of 5 μg/mL. Conclusion: The complex was able to overcome solubility problems and could be used in inflammatory disease.