Enzymes Inhibition, Antimicrobial, Antibiofilm and Anti-quorum Sensing Properties of Essential Oils from Selected Lamiaceae Plants

Objective Lamiaceae plants have high aromatic and medicinal qualities. This work reports the chemical composition of essential oils (EOs) from Thymus capitatus, T. fontanesii and Lavandula stoechas together with their inhibitory effects of selected enzymes and microbial virulence factors. Methods EOs were obtained by hydrodistillation and their chemical compositions determined by GC-FID/GC-MS. The enzyme inhibition of EOs on acetylcholinesterase (AChE), butyrylcholinesterase (BChE), α-amylase, α-glucosidase, urease and tyrosinase were investigated alongside antimicrobial, antibiofilm and quorum-sensing inhibitions (QSI) against a range of bacteria and fungi. Results In EOs from T. capitatus, T. fontanesii and L. stoechas, 36 (100%), 27 (100%) and 42 (100%) compounds were identified respectively. High amounts of oxygenated monoterpenoids were identified in T. capitatus (83.11%), T. fontanesii (72.77%) and L. stoechas (96.53%). At 200 µg/mL, L. stoechas EO exhibits the highest anticholinesterase activity of 56.63 ± 0.79% (AChE) and 71.45 ± 0.37% (BChE), compared to galantamine with 92.22 ± 0.18% (AChE) and 80.37 ± 0.27% (BChE). At 200 µg/mL, T. capitatus EO exhibits good inhibition of α-glucosidase (64.89 ± 0.82%) and α-amylase (62.44 ± 0.78%) compared to acarbose with inhibitions of 67.30 ± 0.45% (α-glucosidase) and 80.56 ± 0.52% (α-amylase). Urease and tyrosinase inhibitions were low. The EOs demonstrated strong antimicrobial activities with inhibition diameters reaching 45.0 ± 0.5 mm and minimal inhibitory concentrations (MIC) as low as 0.007 ± 0.32% v/v. At MIC and sub-MIC concentrations, the EOs inhibited biofilm formation in a concentration-dependent manner. Gram-positive and candida biofilms were relatively more susceptible. EOs inhibited violacein production against C. violaceum CV12472, with T. fontanesii EO being most potent. QSI zones against C. violaceum CV026 were large and L. stoechas EO was most active. EOs inhibited swimming and swarming motilities against P. aeruginosa PA01. Conclusion T. capitatus, T. fontanesii, and L. stoechas are rich in bioactive EOs which can be used to mitigate enzymes related ailments such as diabetes and Alzheimer's disease and attenuate virulence factors in pathogenic bacteria.