Iranian Medicinal Plants Society Journal of Medicinal plants and By-products 2322-1399 15 3 2026 05 01 A Comparative Study of Headspace and Hydro-Distillation Techniques for Volatile Compounds in Thyme Species across Drought Stress and Phenological Stages 334 346 134808 10.22034/jmpb.2025.370397.2032 EN Shahrbanoo Abbasi Department of Plant Breeding and Biotechnology, Shahrekord University, Iran Sadollah Houshmand Department of Plant Breeding and Biotechnology, Shahrekord University, Iran Tayebeh Ahmadi Department of Medical Laboratory Science, College of Science, Knowledge University, Kirkuk Road, Erbil 44001, Iraq Journal Article 2025 08 14 Variations in essential oils and phenolic compounds of <em>T. daenensis</em>, <em>T. armeniacus</em>, and <em>T. vulgaris</em> were investigated at two phenological stages: 50 and 100% flowering. The volatile components of these species extracted using headspace and hydrodistillation techniques were analyzed via gas chromatography-mass spectrometry (GC-MS) under two water stress conditions (90 and 50% field capacity). GC-MS analysis identified the major constituents, including thymol (5.175–51.53%), carvacrol (1.77–24.52%), γ-terpinene (3.95–23.66%), and p-cymene (3.35–24.50%), in the three species using the hydrodistillation method. Maximum thymol content of 51.53% and 43.20% was recorded in <em>T. daenensis</em> during 100% flowering under 90 and 50% FC conditions, respectively. A decline in thymol content in <em>T. daenensis</em> and <em>T. vulgaris</em> was recorded as a decrease from 90 to 50% FC, while <em>T. armeniacus</em> showed an increase. In the headspace method, different compounds were identified as the primary components. Notably, thymol (7.68–54.34%) was identified as the dominant compound in <em>T. daenensis</em>. Drought stress significantly increased thymol composition at the 50% flowering stage but reduced it at the 100% flowering stage. Hierarchical clustering and principal component analysis revealed three distinct groups, separating the compounds identified by the headspace and hydrodistillation methods. The findings suggest that hydrodistillation is more reliable for determining the true concentrations of compounds. https://jmpb.areeo.ac.ir/article_134808_fc60788dff95d0dc36d77b3ffaab2087.pdf