Investigation of the effects of hypericum perforatum L. extract on the effectiveness of hyaluronic acid based gel formulation In Vitro conditions

The skin protects the body against external factors, regulates heat, sense perception, regulates moisture and is involved in some metabolic processes. Starting from the age of 20, the skin loses its elasticity and its moisture level decreases due to external effects caused by environmental factors such as reactive oxygen species (ROS), DNA mutations, telomere shortening, hormonal changes, UV radiation (UVR), smoking, chemicals and trauma. Therefore, in order to increase skin elasticity and keep the skin moist, it is important to provide components suitable for the skin and connective tissue and to choose the safest formula that can effectively penetrate the skin. The microemulsion systems used in the formulation are transparent, thermodynamically stable and have great potential in topical applications, especially in personal care products. Recently, Hyaluronic Acid-based formulations are significantly effective in moisturizing the skin, maintaining skin elasticity and being a natural antioxidant and antimicrobial substance, especially due to their high water retention capacity (1000 times their own weight). However, in order to develop formulations and increase their effect on the skin, they should be developed with excipients. Hypericum perforatum L.. plant reduces inflammation in the skin by inhibiting cytokine production with Flavonoids and Polyphenols in its content, while providing protection against free radicals with hypericin and delaying the aging process by supporting the skin repair process. The aim of this thesis is to create moisturizing products by adding St. John's Wort oil to the hyaluronic acid-based gel formulation and to determine the microbial safety and subsequent skin membrane permeability of the products created. Within the scope of the proposed project, firstly Hypericum perforatum L.. plant was provided in oil form due to its ease of use in formulations. Then, hyaluronic acid-based gel (HA) formulation was created using auxiliary components. Hypericum perforatum L.. oil was added to the created formulation and Hyaluronic Acid-Hypericum perforatum L. complex gel (HAHP) formulation was created. In order to determine the product safety of the obtained HAHP and HA formulations, microbial analyses were performed to determine the Total Bacteria Count, Salmonella and Staphylococcus Aereus, E. Coli and Coliform microorganisms. After the microbial analysis, a preservative efficacy test was applied to the products. Then, HA and HAHP formulations were subjected to a 60-day stability test at 25 °C and 45 °C, 60% humidity. Then, in vitro skin permeability of HA and HAHP formulation on the skin surface was comparatively analyzed using the Franz Diffusion Cell method. When the hyaluronic acid-based gel formulation was applied in nominal amounts of the determined formula, the HA and HAHP product turned into a gel form. As a result of microbial analysis of HA and HAHP products, total microorganism count for HA was found to be 18, total mold and yeast count: 11, Staphylococcus aereus: 1, Eschericia Coli and Coliform: 2, Salmonella: 0 and Candida Albicans: 0. For HAHP, total microorganism count was found to be 11, total mold and yeast count: 5, Staphylococcus aereus: 1, Eschericia coli and Coliform: 0, Salmonella: 0 and Candida albicans: 0. According to the preservative efficacy test results, the antimicrobial effect of Hypericum Perforatum in the formulation of HAHP was also utilized and it was determined that it resulted in a 12.5% logarithmic decrease compared to the HA product and its effectiveness was higher. According to the 60-day stability results of the products, it was observed that they were within the determined acceptance limits and no pHysical difference occurred. HA and HAHP in vitro membrane permeabilities were found to be 5.22×10−8 mol/cm² and 3.47×10−8 mol/cm², respectively. The information and outputs to be obtained within the scope of the project will enable the comparative determination of the moisturizing effect of Hyaluronic Acid-based gels and their forms combined with oils on the skin surface and the in vitro skin permeability, and will determine their microbial and protective effectiveness. We also believe that we have shed light on the missing data in the literature for other studies to be conducted on this subject. Keywords: Formulation, Skin, Microbial, Stability, Microbial, Skin Epithelial Cell, Hyaluronic Acid, Hypericum perforatum L. Oil, Franz Diffusion, Skin Permeability