Seasonal Variation in the Chemical Composition and Antimicrobial Activity of Essential oil Obtained from Moroccan Lavender Lavandula maroccana Murb. Collected from the Wild

Abstract

Background: Lavandula maroccana Murb. is renowned for its valuable essential oil (EO), with a complex chemical composition and potent antimicrobial properties, which can be subjected to environmental influences. The objective of the present study was to assess how seasonal variations affect the yield, chemical composition and antimicrobial activity of Lavandula maroccana Murb. EO. Methods: The plant materials were collected throughout the four seasons and subjected to EO extraction using hydro-distillation method. The chemical composition was analyzed using gas chromatography/mass spectrometry (GC/MS), while the antimicrobial properties were evaluated using disc diffusion and microdilution assays against four yeasts ( Candida albicans, C. glabrata, C. krusei, and C. parapsilosis), and six pathogenic bacteria ( Staphylococcus aureus, Micrococcus luteus, Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa and Klebsiella pneumoniae). Results: The highest EO yield was recorded from the samples collected in autumn (0.19%), while the spring harvest yielded the lowest EO production (0.06%). The GC/MS analysis identified 41 different compounds, with notable variations in the major compound, carvacrol, which ranged from 29.33% to 60.60%. The summer collections contained the highest concentration of carvacrol. Antimicrobial testing, revealed that EOs obtained from all seasons displayed substantial activity against both bacteria and yeast strains. Notably, the summer-harvested EO showed the most potent antimicrobial effects, with inhibition zone and MIC values ranging from 15.32 ± 0.45 mm to 24.09 ± 0.65 mm and 0.16 mg/mL to 2.50 mg/mL, respectively. Conversely, the spring-harvested EO showed the least antimicrobial activity. Conclusion: These findings emphasize the importance of harvesting L. maroccana during the summer and/or autumn to maximize the EO yield and carvacrol content, thereby enhancing its antimicrobial effectiveness.