Comparative GC-MS profiling of wild Calamintha incana leaf essential oils: influence of geographical origin on chemical composition

Herbal medicine is widely practiced in Palestine, largely due to the region's diverse topography, which gives rise to varied climatic conditions and fosters rich biodiversity. Calamintha incana (C. incana) is among the most widely utilized medicinal plants in herbal teas, traditionally esteemed for its therapeutic effects and distinctive aroma. The essential oils extracted from wild C. incana are rich in volatile and semi-volatile secondary metabolites, whose composition can vary with geographic origin, environmental conditions, and harvest time. The current study aims to investigate these metabolites in the leaves of wild C. incana using steam distillation (SD) and gas chromatography–mass spectrometry (GC-MS). It is hypothesized that the bioactive compounds present in wild populations may possess therapeutic potential. Air-dried leaves were collected from ten different locations across Palestine. Essential oils were extracted via SD, yielding an average of approximately 0.4% (wt/wt). The oils were subsequently analyzed using GC-MS in electron impact (EI) mode. Seventeen components were separated with high resolution and identified by comparison with the NIST mass spectral library and Kovats retention indices (KIs) of authentic standards. The analysis revealed pulegone, p-menthan-3-one, and caryophyllene oxide as the major constituents. Pulegone was the dominant component in all samples, with concentrations ranging from 28.64% to 58.97%.