Department of Range and Watershed Management, Faculty of Natural Resources and Earth Sciences, University of Kashan, Kashan, Iran.
PLoS One. 2022 Oct 6;17(10):e0273987. doi: 10.1371/journal.pone.0273987. eCollection 2022.
The diversity found in the chemical compounds of a single species in different regions results in different biologic characteristics which can be considered as a strong source for identifying new chemotypes. Hymenocrater incanus Bunge and Dracocephalum kotschyi Boiss. are exclusive species of the Lamiaceae family which grow in the western and central habitats of Iran. This study was designed and carried out to determine the yield, identify the chemical compounds, and evaluate the antimicrobial characteristics of the essential oil (EO) of these two species in Iran for the first time.
The flowering twigs of the species D. kotschyi and H. incanus were collected from the villages of Totmach and Kamu in Isfahan province respectively, in May 2019. The EO of these plants was extracted and separated using the water distillation method, utilizing the Clevenger device. The EO compounds were analyzed using a gas chromatograph coupled with a mass spectrometer (GC-MS). The evaluation of antimicrobial characteristics was carried out by determining the growth inhibition zone implementing the Agar method, the minimum inhibition concentration (MIC), and the minimum bactericidal/fungicidal concentration (MFC/MBC) utilizing liquid dilution culture.
The results indicated that the highest yield belonged to the EO of D. kotschyi at %2.6 (w/w). In this EO there were citral (%25.44), neral (%20.87), α-pinene (%14.48), trans-geranic acid methyl ester (%9.74), and D-limonene (%6.87). Moreover, H. incanus had the dominant compounds (-)-Spathulenol (%12.61), caryophyllene (%10.00), linolenic acid (%8.54), 1,8-cineole (%5.95), palmitic acid (%5.35), and α-cadinol (%5.17). The largest diameter of growth inhibition zone belonged to the H. incanus EO against the Gram-positive bacteria S. pyogenes (17.67mm). The strongest inhibition activities in the form of growth inhibition diameter exhibited by the D. kotschyi EO were against the Gram-negative bacteria S. paratyphi-A serotype ( 12 mm), K. pneumoniae, and Sh. dysenteriae (~ 11 mm) which was significant compared to the Gram-positive rifampin (~ 8 mm).
It can be seen that these species are new chemotypes with special and novel chemical compounds which can potentially be used to manufacture natural antibiotics against some bacterial strains.
同一物种在不同地区的化合物多样性导致不同的生物学特性，这可以被认为是识别新化学型的强大来源。Hymenocrater incanus Bunge 和 Dracocephalum kotschyi Boiss. 是唇形科特有的物种，生长在伊朗西部和中部的栖息地。本研究旨在首次确定这两个物种在伊朗的产率、鉴定化合物，并评估其精油（EO）的抗菌特性。
2019 年 5 月，分别从伊斯法罕省的托塔马赫和卡穆村采集了 D. kotschyi 和 H. incanus 的开花小枝。利用克利夫兰装置，通过水蒸馏法从这些植物中提取和分离精油。使用气相色谱-质谱联用仪（GC-MS）分析 EO 化合物。通过琼脂法测定抑菌圈、最小抑菌浓度（MIC）和最小杀菌/抑菌浓度（MBC/MFC）利用液体稀释培养来评估抗菌特性。
结果表明，D. kotschyi 的 EO 产率最高，为 2.6%（w/w）。在这种精油中，有柠檬醛（25.44%）、橙花醛（20.87%）、α-蒎烯（14.48%）、反式香叶酸甲酯（9.74%）和 D-柠檬烯（6.87%）。此外，H. incanus 的主要化合物为（-）-spathulenol（12.61%）、石竹烯（10.00%）、亚麻酸（8.54%）、1,8-桉叶素（5.95%）、棕榈酸（5.35%）和α-卡波烯醇（5.17%）。抑菌圈直径最大的是 H. incanus EO 对革兰氏阳性菌 S. pyogenes（17.67mm）的抑制作用。D. kotschyi EO 以抑菌圈直径形式表现出最强的抑制活性，对革兰氏阴性菌 S. paratyphi-A 血清型（12mm）、K. pneumoniae 和 Sh. dysenteriae（11mm）的抑制作用显著优于革兰氏阳性菌利福平（8mm）。
可以看出，这些物种是具有特殊和新颖化学化合物的新型化学型，可能被用于制造针对某些细菌株的天然抗生素。
