Efficacy of Laurus nobilis leaves essential oil for antimicrobial and antioxidant activities

Abstract

This study aims to characterize essential oils extracted (EOEs) from Laurus nobilis L. leaves via hydrodistillation (HD) using the Clevenger apparatus, microwave-assisted hydrodistillation (MWAHD), and water steam entrainment (WSE), and analyze their antimicrobial and antioxidant activity. The EOE yield obtained by MWAHD was 0.74% for a contact time of 40 min, whereas it reached 0.52 and 0.42% by HD and WSE for 200 min. Antioxidant activity results revealed that the extracted essential oils are excellent natural antioxidants and very effective oxidation inhibitors with a minimum concentration IC₅₀ of 0.254 (HD), 0.318 (MWAHD), and 0.025 mg/g (WSE). GC-MS analysis of the volatile compounds revealed the presence of 15 compounds in the Clevenger and MWAHD extracts, with 85.83 and 72.41% respectively, relative amounts, whereas 16 compounds were found in the WSE extract, representing 87.23% of the total compounds. All EOEs contained almost the same dominant components: 1,8 cineole (24.06% for HD; 12.04% for MWAHD and 29.94% for WSE), linalool acetate (10.86%, 11.74%, 12.72%), alpha-terpineol acetate (20.02%; 18.28%, 15.07 %), methyl isoeugenol (7.99%; 11.05% and 8.50%), iso eugenol (2.56%, 3.96% and 2.93%), limonene compounds (1.31%, 3.158% and 1.24%),  espatulenol (1.25%, 1.94%, 1.25%). and cadinol (1.01%, 1.59%, 0.11%), respectively. EOE's microbiological study was carried out using the disk method for bacterial sensitivity strain determination. EOEs were found to be effective against both Gram-positive and Gram-negative bacteria in this study, but the WSE approach was more effective, with a minimum inhibition and inhibition zone values of 1.56 mg/mL and 23.5 mm respectively. Further studies on the effect of dominant compounds in these EOEs could help to highlight their antibacterial and therapeutic importance, and hence their use in medical formulations.