Chemical composition, angiotensin I-converting enzyme inhibitory, antioxidant and antimicrobial activities of essential oil of Tunisian Thymus algeriensis Boiss. et Reut. (Lamiaceae)

The present study describes chemical composition, angiotensin I-converting enzyme (ACE) inhibitory, antioxidant and antimicrobial activities of the essential oil of wild growing Thymus algeriensis Boiss. et Reut. (Lamiaceae), a traditional medicinal plant which is mainly endemic in Tunisia and Algeria. The essential oil from the fresh leaves and flowers of T. algeriensis were extracted by hydrodistillation and analysed by GC and GC/MS. Fifty-seven compounds were identified accounting for 97.71% of the total oil, where oxygenated monoterpenes constituted the main chemical class (44.85%). The oil was dominated by camphor (7.82%), 4-terpineol (7.36%), α-pinene (6.75%), 1,8-cineole (5.54%) and cis-sabinene hydrate (5.29%). The T. algeriensis essential oil was found to possess an interesting inhibitory activity towards ACE with an IC50 value of 150 μg/ml. The obtained results also showed that this oil can act as radical scavengers (IC50 = 0.8 mg/ml) and displayed a lipid peroxidation inhibitory activity (IC50 = 0.5 mg/ml) as evaluated by 2,2-diphenyl-1-picrylhydrazyl and β-carotene bleaching methods, respectively. Furthermore, the oil was tested for antimicrobial activity against six bacterial strains and two fungal strains. The inhibition zones and minimal inhibitory concentration values of microbial strains were in the range of 13.5–64 mm and 1–6 μl/ml, respectively. The oil exhibited remarkable inhibitory activity against fungal and Gram-positive bacteria strains.

Research highlights▶ A new essential oil chemotype of Thymus algeriensis was reported. ▶ This oil possesses an inhibitory activity towards angiotensin I converting enzyme. ▶ The T. algeriensis oil exerted a strong antifungal activity. ▶ This oil can act as radical scavengers and displayed a lipid peroxidation inhibitory activity.