Comparative Evaluation of the Essential Oil Chemical Variability and Antimicrobial Activity between Moroccan Lavender Species

Abstract

Background: The present study was conceived to compare the chemical composition and the related antimicrobial activity of essential oils (EOs) obtained from nine commonly used Moroccan lavender species, namely L. mairei, L. multifida, L. tenuisecta, L. maroccana, L. latifolia, L. pedunculata subsp. atlantica, L. stoechas, L. angustifolia and L. dentata. It aimed to classify these widely used Moroccan lavenders, based on their chemical profiles and antimicrobial effectiveness against some human pathogenic microorganisms. Methods: Plant aerial parts were steam-distilled and the obtained EOs were initially analyzed using gas chromatography/mass spectrometry (GC/MS), then investigated for their antimicrobial activity against six bacteria and four candida strains, using disc diffusion and broth microdilution methods. Results: The chemical analyses showed that all the EOs investigated were classified as oxygenated monoterpene-rich oils (61.78%–92.46%). Hierarchical cluster analysis (HCA) based on the EO chemical compositions enabled the classification of these Moroccan lavender species into four distinct chemical groups: a carvacrol group (Group I), comprising the species L. tenuisecta, L. maroccana and L. mairei, a carvacrol/camphor group (Group II), represented by the species L. multifida, a camphor group (Group III), composed of L. dentata, L. stoechas, L. pedunculata subsp. atlantica, L. latifolia, and a camphor/endo-borneol/1,8 cineole group, represented by L. angustifolia (Group IV). The highest antimicrobial activity was observed for oils obtained from L. tenuisecta, L. maroccana and L. mairei (carvacrol group), with inhibitory zone diameters ranging from 10.30 ± 0.16 to 35.34 ± 0.85 mm, and minimum inhibitory concentration (MIC) and minimum microbicidal concentration (MMC) ranging from 0.039 mg/mL to 5 mg/mL. L. multifida EO (carvacrol/camphor group) showed potent activity, while the lavender EOs from groups III and IV demonstrated the weakest activity. Conclusions: These results support the potential use of some native Moroccan lavenders, particularly those characterized by carvacrol and/or carvacrol/camphor rich oils, as promising sources of natural antimicrobials to combat some human infectious diseases.