Chemical Composition, Antioxidant, Anti-Diabetic, Anti-Acetylcholinesterase, Anti-Inflammatory, and Antimicrobial Properties of Arbutus unedo L. and Laurus nobilis L. Essential Oils.

The objectives of this work were to determine the phytochemical composition and antioxidant, anti-diabetic, antibacterial, anti-inflammatory, and anti-acetylcholinesterase properties of Arbutus unedo L. and Laurus nobilis L. EOs. The antioxidant effects were estimated using four complementary methods. In addition, the anti-diabetic activity was assessed by targeting three carbohydrate-hydrolyzing enzymes, namely α-amylase, α-glucosidase, and lipase. The anti-inflammatory and anti-acetylcholinesterase effects were evaluated by testing the inhibitory potential of both plants on lipo-oxygenase and acetylcholinesterase (AChE), respectively. The antimicrobial activity of these oils was evaluated using disc-diffusion, minimum inhibitory concentration (MIC), and minimum lethal concentration (MLC) tests. The chemical composition of L. nobilis essential oil (EO) was dominated by eucalyptol (36.40%), followed by α-terpineole (13.05%), α-terpinyl acetate (10.61%), linalool (10.34%), and northujane (5.74%). The main volatile compounds of A. unedo EOs were decenal (13.47%), α-terpineol (7.8%), and palmitic acid (6.00%). L. nobilis and A. unedo EOs inhibited α-amylase with IC 50 values of 42.51 ± 0.012 and 102 ± 0.06 µg/mL, respectively. Moreover, both oils inhibited the activity of α-glucosidase (IC 50 = 1.347 ± 0.021 µg/mL and IC 50 = 76 ± 0.021 µg/mL) and lipase (IC 50 = 21.23 ± 0.021 µg/mL and IC 50 = 97.018 ± 0.012 µg/mL, respectively). In addition, L. nobilis EO showed an anti-AChE activity (IC 50 = 89.44 ± 0.07 µg/mL) higher than that of A. unedo EO (IC 50 = 378.57 ± 0.05 µg/mL). Regarding anti-inflammatory activity, in vitro assays showed that L. nobilis significantly inhibits (IC 50 = 48.31 ± 0.07 μg/mL) 5-lipoxygenase compared to A. unedo (IC 50 = 86.14 ± 0.05 μg/mL). This was confirmed in vivo via a notable inhibition of inflammation recorded after 6 h of treatment in both plants at a dose of 50 mg/kg. The microbiological results revealed that EOs from both plants inhibited the growth of all tested organisms except P. aeruginosa , with the highest antimicrobial effect for L. nobilis . The results of these tests showed that these two plants possess remarkable biological and pharmacological properties, explaining their medicinal effects and suggesting them as promising sources of natural drugs.