Preparation and Performance Evaluation of Pinus sylvestris L. Essentıal Oil Loaded Nanoemulsions for Possible Antimicrobial Topical Skin Applications

Abstract

The leaf essential oil of Pinus sylvestris L. has high potential for use in pharmaceutical and cosmetic applications, and is important for its antimicrobial, anti-inflammatory, and antioxidant properties. However, due to the low physicochemical stability and the potential for skin sensitization upon direct application of essential oils, they need to be formulated in appropriate dosage forms for topical application. Nanoemulsions are kinetically stable oil/water systems with droplet sizes of 20-200 nm and are suitable carrier systems for increasing the stability and bioavailability of essential oils and reducing skin sensitization. This study aimed to develop a nanoemulsion-structured lotion form containing essential oil as an internal phase. Initially, the chemical composition of the essential oil was determined by GC-FID/MS; a total of seven compounds were identified, revealing that the oil contained a large proportion of monoterpenes. The biological activity of Pinus sylvestris L. leaf essential oil is due to its high concentration of α-pinene, β-pinene and limonene. Following, preformulation studies were carried out by preparing nanoemulsions containing various ratios of essential oil, surfactant (Kolliphor HS15) and co-surfactant (Transcutol) by using the ultrasonication method. Between 12 formulations, 1% (w/w) essential oil loaded 4 formulations that had different surfactant and co-surfactant content were selected as optimized formulas for further characterization. Droplet sizes, PdI values, and pH values of these formulas were found to be in the range of 21.62-93.59 nm, 0.090-0.249, zeta potentials (+3 to -8 mV) and (4.14-5.14) respectively. Additionally, no significant changes in these parameters were observed during the 30-day stability studies (p>0.05). Antimicrobial analyses were performed by the CLSI microdilution method, and MIC values were determined. Compared to the essential oil, essential oil loaded nanoemulsions showed lower MIC values; formulations that had 1:2 and 1:3 surfactant:cosurfactant ratios, respectively, in particular, provided 4-25 times greater inhibition against Grampositive bacteria and Streptococcus spp. These results demonstrate that P. sylvestris L. essential oil loaded nanoemulsion structured lotion forms are promising stable formulas for possible antimicrobial dermatologicalapplications.