STUDY OF METAL IONS EFFECTIVENESS TO INCREASE THE ANTIOXIDANT ACTIVITY OF RHAMNOLIPIDS IN NANOPARTICLE SYSTEMS

• Main Author: Keumala Fitri, Ika
• Format: Theses
• Language: Indonesia
• Subjects: Kimia
• Online Access: https://digilib.itb.ac.id/gdl/view/68112
• Institution: Institut Teknologi Bandung

High levels of free radicals in the body (oxidative stress) make antioxidants that can be entered into the body through food, beverages, and/or drugs (exogenous antioxidants) become important materials to be developed. Rhamnolipids have the ability as antioxidants at low concentrations but are not as good as antioxidants commonly sold in the market such as ascorbic acid. One strategy to overcome this is the use of nanotechnology in the form of the formation of hybrid nanoparticles between rhamnolipids and metal ions. This study aimed to synthesize rhamnolipid nanoparticles with the addition of three metal variations (Fe3+, Cu2+, and Co2+) using the coprecipitation method to study the physicochemical properties of the three nanoparticles and to study the effect of the addition of the three ions on the activity of rhamnolipids as an antioxidant. The synthesized nanoparticles were then characterized and studied for their physicochemical properties using UV-Vis spectrophotometry, Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), atomic absorption spectroscopy (AAS), transmission electron microscopy (TEM), and particle size analysis (PSA). The three nanoparticles were also tested for their activities using the DPPH assay method. The synthesis of metal ion-rhamnolipid nanoparticles resulted in brown rhamno-Fe solids, turquoise rhamno-Cu solids, and greenish-brown rhamno-Co solids. Based on the UV-Vis absorbance data, it was seen that there was a change in the metal ion ligand which was previously water to rhamnolipid. Encapsulation of rhamnolipid was further proven by looking at the absorption peak of about 3300 cm-1 in the FTIR spectrum of the three nanoparticles. In addition, the three nanoparticles also showed an absorption character around the fingerprint region which indicated the vibration of the metal ion bonding with the O atom of the rhamnolipid. Further EDS results showed the presence of C and O atoms from each nanoparticle which indicated the occurrence of rhamnolipid encapsulation. In addition, each nanoparticle was found to contain Fe in rhamno-Fe, Cu in rhamno-Cu, and Co in rhamno-Co. Based on the AAS results, the mole ratio of metal:rhamnolipid ions in each nanoparticle were 1:6 for rhamno-Fe, 1:4 for rhamno-Cu, and 1:6 for rhamno-Co; indicates that rhamno-Fe and rhamno-Co have an octahedral shape, while rhamno-Cu has a tetrahedral shape. Based on the ratio between the moles of metal ions and rhamnolipids, rhamnolipids may act as monodentate ligands. The three nanoparticles have a rough surface and each nanoparticle is spherical based on the results of SEM and TEM analysis. Each nanoparticle has a tendency to form aggregates, but still has high antioxidant activity with an increase in the maximum antioxidant inhibition of rhamno-Co by 40.39%, rhamno-Cu by 39.56%, and rhamno-Fe by 9.82% from inhibition. maximum standard rhamnolipid. The three nanoparticles also had better effectiveness with a decrease in the IC50 value of standard rhamnolipids of 0.37 mg/mL for rhamno-Fe, 0.14 mg/mL for rhamno-Cu, and 0.58 mg/mL for rhamno-Co. The difference in the effect on inhibition was most likely due to differences in the size of the nanoparticles, while the difference in IC50 of the three nanoparticles could be due to the number of rhamnolipids that became ligands for one metal ion. Based on the antioxidant test results of the three nanoparticles, rhamno-Co is the most promising nanoparticle to be further developed and applied in industry.