This study obtained essential oils (EOs) from fresh and dried leaves of Coridothymus capitatus collected from two geographically distinct Palestinian locations: Hebron and Bethlehem. Oils were produced by hydrodistillation from plant aerial parts. Chemical profiling was carried out using gas chromatography–mass spectrometry (GC-MS) to determine the relative composition of volatile constituents.
The analysis identified oxygenated monoterpenes as the dominant chemical class across the samples, comprising between 69.03% and 74.44% of the total oil composition. The two major phenolic monoterpenes detected were thymol and carvacrol, consistent with prior literature describing phenolic-rich profiles for this species.
GC-MS results revealed a clear chemotypic divergence between the populations sampled in Hebron and Bethlehem. Oils from Hebron were characterized as thymol-rich, whereas Bethlehem samples were characterized as carvacrol-rich. This spatial variation in the relative abundance of phenolic monoterpenes reflects chemotypic heterogeneity within Palestinian C. capitatus populations and aligns with reports of significant chemovarietal variability across the Mediterranean basin.
The study emphasizes that geographic origin is a principal determinant of essential oil profile in this species. Environmental and ecological differences across short distances in the Holy Land—including altitude, climate, precipitation, and soil characteristics—are discussed as likely contributors to the observed chemical polymorphism.
The investigators compared oils obtained from fresh and from dried leaves to assess the impact of post-harvest processing on phytochemical composition. The authors report that both geographic origin and post-harvest drying influenced the chemical composition and biological activities of the EOs. Specific compositional shifts attributable to drying were observed but numerical breakdowns of each component by fresh versus dried material are presented in the paper's tables (figures and tables referenced in the original manuscript).
Antioxidant capacity of the EOs was evaluated using the DPPH radical-scavenging assay across a concentration range of 0.333–33.33 µg/mL. At the highest experimentally tested concentration (33.33 µg/mL), the abstract reports DPPH inhibition using two different sets of values in duplicate text: one instance lists inhibition ranging from 28.21 ± 0.76 to 34.40 ± 0.85% among the oils, and another instance lists inhibition ranging from 37.50 ± 0.83% to 52.08 ± 0.36% among the oils. In both descriptions the Hebron-fresh oil is reported as showing the highest activity. The paper therefore reports antioxidant activity consistent with measurable but moderate radical-scavenging effects, and highlights the contribution of phenolic constituents such as thymol and carvacrol to this activity.
The essential oils were tested against a panel of Gram-positive and Gram-negative bacteria. The authors report substantial antibacterial effects, with minimum inhibitory concentrations (MICs) ranging from 25 to 100 µg/mL. These antimicrobial effects are attributed primarily to phenolic monoterpenes, which are known to disrupt microbial cell membranes, increase permeability, and cause leakage of intracellular contents.
The study indicates that both thymol- and carvacrol-rich oils demonstrated antibacterial activity, reinforcing the biological relevance of these phenolic constituents in conferring broad-spectrum antibacterial effects.
Antifungal testing revealed strong inhibitory effects of the oils against several phytopathogenic fungi. Notably, Botrytis californica and Fusarium species showed high sensitivity, with MICs reported as low as 6.25 µg/mL. Such low MIC values indicate potent antifungal activity in vitro, supporting potential use of C. capitatus EOs in sustainable crop protection strategies.
The antifungal activity is discussed in the context of membrane-disruptive mechanisms similar to those proposed for antibacterial effects, with phenolic monoterpenes implicated as the active constituents.
The authors conclude that C. capitatus populations in Palestine exhibit marked chemotypic variation tied to geographic origin and post-harvest handling. The dominance of oxygenated monoterpenes and the prominence of thymol and carvacrol underpin measurable antioxidant, antibacterial, and antifungal activities observed in the study.
Potential applications noted include use of these oils or their constituents in natural food preservation, as agents in sustainable crop protection, and in other contexts that may benefit from natural antimicrobial and antioxidant constituents. The study also highlights gaps in comparative data for Palestinian populations and underscores the influence of environmental and processing variables on EO composition and bioactivity.
Note: the abstract contains duplicated text reporting two differing ranges for DPPH inhibition at the highest tested concentration. Both ranges are included above as reported in the source; further detail and tabulated data are available in the full manuscript tables and figures referenced by the authors.