Synthesis and Characterization of Betulinic Acid-Aminopropyltriethoxysilane Compounds and Their Assembly onto Nanoporous Alumina Surfaces as Potential Therapeutic Agents

The present study describes the synthesizing and attaching of betulinic acid-aminopropyl triethoxysilane (BA-APTES) on top of the nanoporous alumina (NA) surface. The NA was fabricated by using electrochemical anodization process under an applied voltage of 40 V for 20 hours resulting in average pore size of 45 nm characterized by Scanning Electron Microscope (SEM). The well-recognized therapeutic compound, betulinic acid (BA) was first extracted from the bark of Melaleuca cajuputi plant and further purified by column chromatography. The purified BA was incorporated with APTES using 1-hydroxybenzotriazole hydrate (HOBt) and O-(Benzotriazol-1-yl)-N,N,N’-tetramethyluronium hexafluorophosphate (HBTU) as a peptide coupling agent. The synthesized BA-APTES was silanized on top of the fabricated NA surface. The aromatic portion of 1H and 13C of the synthesized BA-APTES compound was validated by means of Nuclear Magnetic Resonance (NMR). The FTIR spectra show emerging peaks at 2900 cm-1 and 1250 cm-1 signifying the present of aldehyde and also aliphatic amine on NA, respectively. With the aid of XPS analysis, the chemical composition of BA-APTES has evidenced that the presence of the compounds on the surface of NA membrane. Hence, the authors suggest that the modified NA surface has a potential to be applied as a new material for therapeutic agent.