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 silicate 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%. DSC and X-ray powder diffraction analyses showed that the adsorbed IBA molecules do not undergo crystallization process within the pores, but are organized in an amorphous form. This fact, combined to the high superficial area of IBA when loaded in MCM-41, improves the whole solubilization process.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. The 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. The property of MCM-41 highlighted in this work could also be exploited in many other fields, such as pharmaceutics, where compound solubility characteristics of compounds are very important.