Salvia mirzayanii and Salvia hypoleuca Essential Oils: Chemical Composition, Alpha-Glucosidase Inhibitory, and Synergistic Effects of Selected Components

Background: Salvia is one of the most important genera belonging to the Lamiaceae family that has been used in various applications in folk medicine and the pharmaceutical and food industries. Objectives: This study investigated the chemical composition, antioxidant activity, and α-glucosidase inhibitory activity of Salvia mirzayanii Rech. f. and Esfand. and Salvia hypoleuca Benth. essential oils (EOs). Additionally, the enzyme inhibitory activity of the mixture of compounds was evaluated to find whether the synergistic effect is responsible for the desired activity or not. Methods: The constituents of S. mirzayanii and S. hypoleuca EOs collected from Fars and Alborz provinces, Iran, were determined using gas chromatography-mass spectroscopy (GC-MS) analysis. They were evaluated for their α-glucosidase inhibitory activity by the determination of para-nitrophenol (pNP), derived from the enzymatic degradation of para-nitrophenol-D-glucopyranoside (pNPG) as the substrate. The activity of the selected components was also tested. Moreover, the antioxidant activity of EOs was evaluated based on the radical scavenging capability (2,2-Diphenyl-1-picrylhydrazyl [DPPH]) assay, and their total phenolic content (TPC) was determined using the Folin-Ciocalteu method in terms of gallic acid equivalent (GAE). Results: In total, 66 compounds were detected in the S. mirzayanii and S. hypoleuca EOs. The results showed that S. mirzayanii EO had more potent antioxidant activity (half-maximal inhibitory concentration [IC50] = 0.77 ± 0.00 mg/mL), higher TPC (78.26 ± 1.26 mg GAE/g EO), and a greater inhibitory effect toward α-glucosidase (IC50 = 55.15 ± 1.60 mg/mL) than S. hypoleuca EO. Furthermore, caryophyllene oxide (IC50 = 19.94 ± 0.26 mg/mL), α-pinene (IC50 = 17.59 ± 0.19 mg/mL), and linalool (IC50 = 38.00 ± 0.22 mg/mL) showed high levels of α-glucosidase inhibitory activity among the major constituents. In addition, the combination of linalool: 1,8-cineole: α-terpineol (40: 35: 25) inhibited this enzyme synergistically (combination index [CI] < 1). Conclusions: The findings indicated that S. mirzayanii EO had a high potential for developing efficient anti-type 2 diabetes agents.