Investigation of antioxidant and antibacterial properties of liposomal formulation of Ulva lactuca extract

Ulva lactuca (Ulvophyceae; Ulvaceae), also known as sea lettuce, is a green macroalgae species that grows in rocky and shallow waters and spreads widely around the world. U. lactuca contains bioactive compounds such as alkaloids, flavonoids, tannins, steroids, saponins and anthraquinones and is known to have many positive effects on health, including antioxidant and antimicrobial effects. On the other hand, liposomes have biocompatible, non-toxic and biodegradable properties. Liposomes are used in the pharmaceutical, food, chemistry and cosmetic industries. Although it has different composition and physical properties according to the application area, there are many different preparation methods. Because of their amphipathic nature, liposomes can encapsulate both hydrophobic and hydrophilic compounds. Depending on a particular release profile, controlled release can be made. Liposomes, which have the ability to be modified with target-specific ligands, increase the integration with the target region. In addition, it protects the therapeutic agent from the metabolism system in the body, thus increasing the effectiveness of the therapeutic agent. In this thesis study, algae materials of U. lactuca collected from Marmara (Bursa) and Aegean (İzmir) seas were extracted at Bursa Technical University and Ege University. Extraction was carried out with Ethanol/Water (80/20 V/V) solvent at 40 °C and room temperature with two separate methods. The antioxidant and antibacterial properties of the obtained extract and the extract-loaded liposomal formulations were investigated. In order to understand the antioxidant capacity of extracts and extract-loaded liposomal formulations, their total phenolic content was investigated by Folin Ciocioultiou method and antioxidant activity was investigated by DPPH radical scavenging activity. According to the results of the total phenolic content determination with the Folin Ciocioultiou method, at a concentration of 100 µg/mL; TPC of Marmara extract was calculated as 5.306 mg GAE/g, while TPC of Aegean extract was found as 7.5 mg GAE/g. The EC50 values of Marmara and Aegean extracts were calculated as 429.21 µg/mL and 834.29 µg/mL, respectively. These values are approximately 30 to 60 times higher than the standard antioxidant ascorbic acid. For the antibacterial effect of U. lactuca extract, firstly, disk diffusion test was performed. Then, their antibacterial activities were evaluated with Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBK) tests. In the disk diffusion test, inhibition zone were 8 mm was determined for each sample, while the liposomal formulations of U. lactuca Marmara and Aegean extracts were determined as 1250 µg/mL against E.coli ATCC 25922 in the MIC test. Both samples were found to be less effective against S. aureus ATCC 25923 and had MIC values of 2500 µg/mL. In the MIC test, it was found that the antibacterial effect of the extract-loaded liposomes was higher than the extracts. It was concluded that MBK values could be reached at higher concentrations than MIC values.