Table 1_Influence of growth stage on the chemical composition, antimicrobial, and antioxidant potential of Cymbopogon martinii (Roxb.) Wats. essential oil.docx

IntroductionCymbopogon martinii (Roxb.) Wats. essential oil (CMEO) exhibits significant variation in composition and bioactivity across different growth stages. Understanding these changes is crucial for optimizing its therapeutic and industrial applications.
MethodsCMEO was extracted at the vegetative, reproductive, and post-reproductive stages using hydro-distillation. Chemical composition was analyzed by GC-MS. Antimicrobial activity was assessed using disc diffusion and direct contact assays, while antioxidant potential was evaluated through DPPH, ABTS, and β-carotene bleaching assays. Correlation analysis was performed to link major bioactive compounds with biological activities.
ResultsA total of 59 compounds were identified, with the reproductive stage showing the highest diversity (49 compounds, 97.86%) and oil yield. Major compounds varied across stages: carveol (20.87%), trans-p-mentha-1(7),8-dien-2-ol (12.9%), and D-limonene (6.2%) dominated the vegetative phase; cis-piperitol (15.27%), cis-p-mentha-1(7),8-dien-2-ol (15.52%), and carvone (3.31%) were abundant in the reproductive phase; while the post-reproductive phase was rich in trans-p-mentha-1(7),8-dien-2-ol (19.58%) and carveol (11.32%). Antibacterial and antifungal activities were highest during the reproductive stage, particularly against Staphylococcus aureus and Alternaria alstroemeriae. Antioxidant potential peaked during the post-reproductive phase, with the lowest IC50 values.
DiscussionCorrelation analysis revealed negative associations between key bioactive compounds (e.g., carvone, D-limonene, α-methylcinnamaldehyde, and (S)-perillyl alcohol) and microbial/oxidative inhibition thresholds, confirming their contribution to CMEO bioactivity. These findings highlight the critical role of harvest timing in maximizing the chemical richness, antimicrobial efficacy, and antioxidant potential of CMEO.

引言 马丁香茅（Cymbopogon martinii (Roxb.) Wats.）精油（CMEO）的化学成分组成与生物活性会随生长阶段的不同发生显著变化。明晰这类变化规律，对于优化其治疗应用与工业开发价值至关重要。方法 本研究采用水蒸馏法，分别在营养生长期、生殖生长期以及生殖后期提取马丁香茅精油。通过气相色谱-质谱联用（Gas Chromatography-Mass Spectrometry, GC-MS）技术分析其化学成分组成；采用纸片扩散法与直接接触试验评估其抗菌活性；通过1,1-二苯基-2-三硝基苯肼（1,1-Diphenyl-2-picrylhydrazyl, DPPH）、2,2'-联氮-双-3-乙基苯并噻唑啉-6-磺酸（2,2'-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid), ABTS）以及β-胡萝卜素漂白试验测定其抗氧化能力。此外，通过相关性分析明确主要生物活性成分与生物学活性之间的关联。结果 本研究共鉴定出59种化学成分，其中生殖生长期的精油成分多样性最高（共49种成分，占总含量的97.86%），且精油得率也最高。各生长阶段的优势化学成分存在显著差异：营养生长期以香芹醇（20.87%）、反式-p-薄荷-1(7),8-二烯-2-醇（12.9%）以及D-柠檬烯（6.2%）为主；生殖生长期的优势成分为顺式-胡椒醇（15.27%）、顺式-p-薄荷-1(7),8-二烯-2-醇（15.52%）与香芹酮（3.31%）；而生殖后期则以反式-p-薄荷-1(7),8-二烯-2-醇（19.58%）与香芹醇（11.32%）为主要成分。抗菌活性方面，生殖生长期的抗菌与抗真菌活性最强，尤其对金黄色葡萄球菌（Staphylococcus aureus）与阿尔斯特雷梅里亚链格孢（Alternaria alstroemeriae）的抑制效果最佳。抗氧化能力则在生殖后期达到峰值，此时半抑制浓度（IC50）值最低。讨论 相关性分析结果显示，关键生物活性成分（如香芹酮、D-柠檬烯、α-甲基肉桂醛以及(S)-紫苏醇）与微生物/氧化抑制阈值呈负相关，证实了这些成分对马丁香茅精油生物活性的贡献。本研究结果明确了采收时机对最大化马丁香茅精油的化学成分丰富度、抗菌效果与抗氧化能力的关键作用。