Antioxidant, Antibacterial, and SIRT1/SIRT3/hTERT Promoter‐Upregulating Effects of Synergistic Rosmarinus officinalis and Salvia officinalis Essential Oils

In this study, the effect of a combination of Rosmarinus officinalis and Salvia officinalis essential oils (EOs) was evaluated. The chemical profile of EOs was determined by Gas Chromatography/Mass Spectrometry (GC/MS). The antibacterial effect of EOs alone was evaluated by the broth micro-dilution method, and the antioxidant activity was determined by 2,2-Diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging and Ferric Reducing Antioxidant Power (FRAP) methods. The antioxidant and antibacterial interaction of the combination of EOs was evaluated through the determination of the fractional inhibitory concentration index (FICI) using the checkerboard method. The anti-aging activity of R. officinalis, S. officinalis, and their combination in a 1:1 (w/w) ratio was evaluated on SIRT1, SIRT3, and hTERT promoters in the human keratinocyte cell line HaCaT. The GC/MS analysis revealed that R. officinalis EO was dominated by 1,8-cineole (28.43% ± 0.32%) and α-pinene (26.62% ± 0.53%). α-thujone (23.98% ± 0.17%), α-pinene (17.59% ± 0.02%), camphor (15.84% ± 0.1%), and 1,8-cineole (15.76% ± 0.11%) were found as the main constituents of S. officinalis EO. Regarding the antioxidant and antibacterial activities, the results showed that R. officinalis EO tested alone showed significant efficacy. The results showed interesting synergistic effects in scavenging DPPH radical (FICI = 0.75) and in ferric reducing power (FICI = 0.50). Moreover, this combination exhibited a synergistic effect against E. hirae (FICI = 0.38), S. aureus (FICI = 0.63), and E. coli (FICI = 0.75), while the additive effect was shown against P. aeruginosa (FICI = 1). The expression level of the SIRT1 promoter in HaCaT cells treated with R. officinalis EO and its combination with S. officinalis EO is significantly higher than that of resveratrol. The results of endogenous SIRT3 expression revealed that the individual EOs and their association induced strong activity, while the strong hTERT promoter expression level was found when the HaCaT cells were treated with R. officinalis EO.