Essential oil composition and biological activities of Coridothymus capitatus collected from two locations in...

Coridothymus capitatus (L.) Reichenb. f. (syn. Thymus capitatus) is a Mediterranean aromatic herb esteemed for its essential oil rich in bioactive phenolic compounds. In the current study, essential oils (EOs) were obtained by hydrodistillation from fresh and dried leaves of C. capitatus collected from Hebron and Bethlehem, Palestine, and evaluated for their chemical composition, antioxidant, antibacterial, and antifungal activities. Gas chromatography-mass spectrometry (GC-MS) analysis showed that oxygenated monoterpenes were the leading class (69.03-74.44%), with thymol and carvacrol as the major constituents. A clear chemotypic divergence was observed between the two locations, with thymol-rich oils in Hebron and carvacrol-rich oils in Bethlehem. Antioxidant activity was evaluated using the DPPH radical-scavenging assay over a concentration range of 0.333-33.33 µg/mL. At the highest experimentally tested concentration (33.33 µg/mL), DPPH inhibition ranged from 28.21 ± 0.76 to 34.40 ± 0.85ᵃ% among the EOs, with Hebron-fresh oil showing the highest activity. Antibacterial tests displayed substantial activity against Gram-positive and Gram-negative bacteria, with MICs between 25 and 100 µg/mL, while antifungal tests revealed strong inhibitory effects against phytopathogenic fungi, particularly Botrytis californica and Fusarium species, with MICs as low as 6.25 µg/mL. The geographical origin and post-harvest drying influenced the chemical composition and biological activities of the EOs, demonstrating chemotypic variation among Palestinian C. capitatus populations. This study provides a comprehensive comparison of EOs from C. capitatus populations from two geographically distinct regions of Palestine and evaluates the effects of post-harvest drying on their phytochemical composition and antioxidant, antibacterial, and antifungal activities. These findings contribute to understanding the chemotypic variation of Palestinian C. capitatus and highlight its potential as a natural source of bioactive compounds for food preservation, sustainable crop protection, and related applications. Coridothymus capitatus (L.) Reichenb. f. (syn. Thymus capitatus) is a Mediterranean aromatic herb esteemed for its essential oil rich in bioactive phenolic compounds. In the current study, essential oils (EOs) were obtained by hydrodistillation from fresh and dried leaves of C. capitatus collected from Hebron and Bethlehem, Palestine, and evaluated for their chemical composition, antioxidant, antibacterial, and antifungal activities. Gas chromatography-mass spectrometry (GC-MS) analysis showed that oxygenated monoterpenes were the leading class (69.03-74.44%), with thymol and carvacrol as the major constituents. A clear chemotypic divergence was observed between the two locations, with thymol-rich oils in Hebron and carvacrol-rich oils in Bethlehem. Antioxidant activity was evaluated using the DPPH radical-scavenging assay over a concentration range of 0.333-33.33 µg/mL. At the highest experimentally tested concentration (33.33 µg/mL), DPPH inhibition ranged from 37.50 ± 0.83% to 52.08 ± 0.36% among the EOs, with Hebron-fresh oil showing the highest activity. Antibacterial tests displayed substantial activity against Gram-positive and Gram-negative bacteria, with MICs between 25 and 100 µg/mL, while antifungal tests revealed strong inhibitory effects against phytopathogenic fungi, particularly Botrytis californica and Fusarium species, with MICs as low as 6.25 µg/mL. The geographical origin and post-harvest drying influenced the chemical composition and biological activities of the EOs, demonstrating chemotypic variation among Palestinian C. capitatus populations. These findings contribute to understanding the chemotypic variation of Palestinian C. capitatus and highlight its potential as a natural source of bioactive compounds for food preservation, sustainable crop protection, and related applications.