Data Sheet 1_Terpenoids as principal bioactive compound of Cissampelos oppositifolia essential oils: enhancing synergistic efficacy with conventional antibiotics.pdf

BackgroundThe rise of antibiotic resistance imposes the search for novel antimicrobial strategies as natural products or its combination with antibiotics. This study investigates the synergistic effects of terpenoids from Cissampelos oppositifolia (C. oppositifolia) essential oil in combination with antibiotics against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The aims were to evaluate the antimicrobial efficacy, analyze functional group modifications and assess molecular interaction.
MethodsEssential oil was extracted from C. oppositifolia by hydro-distillation. The EO was analyzed for terpenoid content via Thin Layer Chromatography (TLC). Antimicrobial activity was assessed using the disc diffusion method and Minimum Inhibitory Concentration determinations (MIC) by broth dilution followed by bactericidal essay (Time-killing). FTIR and UV spectroscopy were employed to detect functional group modifications in terpenoid-antibiotic combinations. Molecular docking studies assessed interaction energies between terpenoids and antibiotics.
ResultsTLC identified α-pinene, δ-carene, and caryophyllene in the EO. δ-Carene exhibited the highest synergy with antibiotics, showing the lowest MIC of 0.04 mg/mL against S. aureus ATCC-43300 and 0.05 mg/mL against E. coli MTCC-739. Time-kill assays demonstrated that α-pinene, δ-carene, and caryophyllene achieved complete bacterial eradication by 4 hours in combination with amoxicillin against E. coli, and by 2 hours against S. aureus in combination with erythromycin. FTIR analysis revealed peak shifts at 1599, 1774, and 2259 cm−1 for amoxicillin + α-pinene, and new peaks at 1648 and 1287 cm−1 for δ-carene + erythromycin. UV spectra indicated potential complex formations. Docking studies showed δ-carene’s strong interaction with erythromycin and amoxicillin, with interaction energies of -96.10 and -87.75 kcal/mol, respectively.
ConclusionTerpenoids from C. oppositifolia enhance the antimicrobial efficacy of antibiotics. Functional group modifications and complex formations suggest that these interactions may contribute to synergistic effects. These findings support the potential use of terpenoid-antibiotic combinations in overcoming antibiotic resistance and warrant further investigation into their mechanisms of action.

**背景** 抗生素耐药性问题日益严峻，推动学界探索以天然产物或其与抗生素联用作为新型抗菌策略。本研究针对对叶地不容（Cissampelos oppositifolia, C. oppositifolia）精油中的萜类化合物与抗生素联合使用时，对大肠杆菌（Escherichia coli, E. coli）及金黄色葡萄球菌（Staphylococcus aureus, S. aureus）的协同抗菌效果展开探究。本研究旨在评估联合疗法的抗菌效能、分析功能基团修饰情况，并解析其分子相互作用机制。
**方法** 采用水蒸馏法提取对叶地不容的精油；通过薄层层析（Thin Layer Chromatography, TLC）分析精油中的萜类成分。采用纸片扩散法评估抗菌活性，通过肉汤稀释法测定最低抑菌浓度（Minimum Inhibitory Concentration, MIC），并后续开展杀菌实验（时间-杀菌曲线法）。采用傅里叶变换红外光谱（Fourier Transform Infrared Spectroscopy, FTIR）与紫外光谱（Ultraviolet Spectroscopy, UV）检测萜类-抗生素联合体系的功能基团修饰情况；通过分子对接实验评估萜类化合物与抗生素之间的相互作用能。
**结果** 薄层层析检测结果显示，精油中含有α-蒎烯、δ-蒈烯与石竹烯。其中δ-蒈烯与抗生素的协同效果最为显著：其针对金黄色葡萄球菌ATCC-43300的最低抑菌浓度低至0.04 mg/mL，针对大肠杆菌MTCC-739的最低抑菌浓度为0.05 mg/mL。时间-杀菌曲线实验表明，α-蒎烯、δ-蒈烯与石竹烯分别与阿莫西林联用时，可在4小时内完全杀灭大肠杆菌；与红霉素联用时，可在2小时内完全杀灭金黄色葡萄球菌。傅里叶变换红外光谱分析显示，阿莫西林与α-蒎烯的混合体系在波数1599、1774与2259 cm⁻¹处出现峰位移；δ-蒈烯与红霉素的混合体系则在1648与1287 cm⁻¹处出现新特征峰。紫外光谱结果提示二者可能形成复合结构。分子对接实验证实，δ-蒈烯与红霉素、阿莫西林均存在较强相互作用，相互作用能分别为-96.10 kcal/mol与-87.75 kcal/mol。
**结论** 对叶地不容精油中的萜类化合物可增强抗生素的抗菌效能。功能基团修饰与复合结构形成的实验结果提示，此类相互作用可能是协同抗菌效果的重要来源。本研究结果证实，萜类-抗生素联合疗法在克服抗生素耐药性方面具有潜在应用价值，同时也为进一步解析其作用机制提供了研究方向。