Effect of MCM-41 on the dissolution rate of the poorly soluble plant growth regulator, the indole-3-butyric acid

The paper reports a new property of MCM-41 mesoporous materials, that is the improvement of the apparent solubility and the dissolution rate of water poorly soluble compounds. The indole-3-butyric acid (IBA), a plant growth regulator, was used as a model poorly soluble compound. The inclusion compound MCM-41-IBA was prepared and the final percent loading resulted 30%. The complex, analyzed by FT-IR, revealed the presence of hydrogen bonds between IBA and MCM-41 silanols, while XR diffraction and differential scanning calorimetry (DSC) demonstrated that the adsorbed IBA was in an amorphous form. This observation paralleled the in vitro release tests that showed for the adsorbed IBA a higher dissolution rate if compared to its crystalline form. In fact, IBA when is included on MCM-41 had twice the solubility of free IBA in water. Then new IBA features when included in the complex revealed to be very interesting for practical purposes, since its effect, as plant growth hormone, is limited by the low solubility. In fact the aqueous dispersion of MCM-41-IBA (500 ppm of IBA) resulted very useful to increase the rooting ability of Olea europaea L. cultivar Leccino, cuttings. (c) 2006 Elsevier Inc. All rights reserved.