α-Terpineol, terpinen-4-ol, and δ-terpineol, isomers of terpineol, are among the compounds that give Cinnamomum longepaniculatum leaf oil its distinguished pleasant smell. The objective of this study was to evaluate the antimicrobial activity of these three isomeric terpineols. The determination of antibacterial activity was based on the minimum inhibition concentration (MIC) and minimum bactericide concentration (MBC). Changes in time-kill curve, alkaline phosphatase (AKP), UV-absorbing material, membrane potential, and scanning electron microscopy (SEM) were measured to elucidate the possible antimicrobial mechanism. α-Terpineol, terpinen-4-ol, and δ-terpineol demonstrated good inhibitory effects against several gram-negative bacteria, particularly Shigella flexneri. MIC and MBC of α-terpineol and terpinen-4-ol were similar (0.766 mg/mL and 1.531 mg/mL, respectively) for S. flexneri, while the MIC and MBC values of δ-terpineol were 0.780 mg/mL and 3.125 mg/mL, respectively. Time-kill curves showed that the antibacterial activities of the tested compounds were in a concentration-dependent manner. Release of nucleic acids and proteins along with a decrease in membrane potential proved that α-terpineol, terpinen-4-ol, and δ-terpineol could increase the membrane permeability of Shigella flexneri. Additionally, the release of AKP suggested that the cell wall was destroyed. SEM analysis further confirmed that S. flexneri cell membranes were damaged by α-terpineol, terpinen-4-ol, and δ-terpineol. Our research suggests that these three isomeric terpineols have the potential of being used as natural antibacterial agents by destroying the cell membrane and wall, resulting in cell death. However, the specific antibacterial activity differences need further investigation.

α萜品醇，萜品烯-4-醇，和δ萜品醇，萜品醇的异构体，是这样的化合物，让间樟油樟叶油其杰出的令人愉快的味道。本研究的目的是评估这三种异构松油醇的抗菌活性。抗菌活性的测定基于最小抑制浓度（MIC）和最小杀菌剂浓度（MBC）。测量了时间-杀灭曲线、碱性磷酸酶 (AKP)、紫外线吸收材料、膜电位和扫描电子显微镜 (SEM) 的变化，以阐明可能的抗菌机制。α-萜品醇、萜品烯-4-醇和δ-萜品醇对几种革兰氏阴性菌，尤其是弗氏志贺氏菌显示出良好的抑制作用. α-萜品醇和萜品烯-4-醇的 MIC 和 MBC 对弗氏S. flexneri相似（分别为 0.766 mg/mL 和 1.531 mg/mL），而 δ-萜品醇的 MIC 和 MBC 值为 0.780 mg/mL 和 3.125毫克/毫升，分别。时间-杀灭曲线表明，受试化合物的抗菌活性呈浓度依赖性。核酸和蛋白质的释放以及膜电位的降低证明α-萜品醇、萜品烯-4-醇和δ-萜品醇可以增加福氏志贺菌的膜通透性。此外，AKP 的释放表明细胞壁被破坏。SEM 分析进一步证实S. flexneri细胞膜被α-萜品醇、萜品烯-4-醇和δ-萜品醇破坏。我们的研究表明，这三种异构萜品醇有可能通过破坏细胞膜和细胞壁，导致细胞死亡而被用作天然抗菌剂。然而，具体的抗菌活性差异需要进一步研究。