Compound composition table of Taihang Chrysanthemum hydrosol with different pretreatments and different open states

为研究太行菊（Opisthopappus taihangensis）在不同开花期纯纯露的挥发性成分差异，以及冻干预处理对其芳香成分的影响，采用超声辅助蒸汽蒸馏法提取太行菊萌芽期、初开期和盛开期鲜花和冻干花精油。使用顶空二维气相色谱联合四极杆串联飞行时间高分辨率质谱法分析挥发性成分。通过计算相对香气活性值（ROAV），采用OPLS-DA模型筛选不同太行菊纯香精中关键差异芳香成分（ROAV > 1，VIP > 1，P < 0.05）。结果表明：太行菊纯香精共鉴定出217种化合物，其中太行菊花（THC-F）纯香精中共有187种化合物，主要由醇类、醚类和酮类组成，主要挥发性成分为桉树醇（4.63–17.57 mg/kg）和顺式菊花醇（2.04–16.14 mg/kg），具有薄荷香、果香甜味和松脂香气;太行菊花冷冻干燥后得到的纯提取物（THC-FD）含有90种化合物，主要是酯类和醚类。主要挥发性成分为桉树醇（0.16–14.90 mg/kg）和（Z）-菊花乙酸醇（2.04–7.84 mg/kg），具有薄荷、柠檬和松脂的香味。OPLS-DA模型分析（ROAV > 1，VIP > 1，P < 0.05）表明，桉树醇和对伞花烯是区分不同开放状态下纯香精与太行菊花的关键芳香成分;桉树醇、醋酸冰片和柠檬醛是区分冻干太行菊花纯提取物和鲜花纯提取物的关键芳香成分。研究表明，挥发性成分丰富、香气更浓郁的盛开期是太行菊提取纯精的最佳时机。此外，冷冻干燥处理可以产生相对较多的酯类化合物和柠檬醛，这些都是关键的芳香成分，为提取具有独特香气的纯香精提供了有价值的参考。

This study aimed to investigate the differences in volatile components of hydrosols of Opisthopappus taihangensis at different flowering stages, as well as the effect of freeze intervention treatment on its aromatic components. Ultrasound-assisted steam distillation was used to extract essential oils from fresh and freeze-dried flowers of O. taihangensis at the bud stage, initial flowering stage, and full bloom stage. Volatile components were analyzed using headspace two-dimensional gas chromatography combined with quadrupole tandem time-of-flight high-resolution mass spectrometry. Key differential aromatic components in different hydrosols of O. taihangensis were screened using the OPLS-DA model by calculating the relative odor activity value (ROAV), with the criteria of ROAV > 1, VIP > 1, and P < 0.05.

The results showed that a total of 217 compounds were identified in the hydrosols of O. taihangensis, among which 187 compounds were found in the hydrosols of fresh O. taihangensis flowers (THC-F), mainly composed of alcohols, ethers, and ketones. The main volatile components were eucalyptol (4.63–17.57 mg/kg) and cis-chrysanthemol (2.04–16.14 mg/kg), which had mint, fruity sweetness, and pine resin aromas. The hydrosol from freeze-dried O. taihangensis flowers (THC-FD) contained 90 compounds, mainly esters and ethers. Its main volatile components were eucalyptol (0.16–14.90 mg/kg) and (Z)-chrysanthemyl acetate (2.04–7.84 mg/kg), which had mint, lemon, and pine resin aromas.

Analysis using the OPLS-DA model (with the criteria ROAV > 1, VIP > 1, P < 0.05) indicated that eucalyptol and p-cymene were the key aromatic components for distinguishing hydrosols at different flowering stages from those of fresh O. taihangensis flowers, while eucalyptol, bornyl acetate, and citral were the key aromatic components for distinguishing the hydrosols of freeze-dried O. taihangensis flowers from those of fresh flowers.

The study demonstrated that the full bloom stage, which has abundant volatile components and a more intense aroma, is the optimal time for extracting hydrosols from O. taihangensis. In addition, freeze-drying treatment can produce relatively more ester compounds and citral, which are key aromatic components, providing a valuable reference for extracting hydrosols with unique aromas.