3个产区沉香燃烧烟气特征化学成分分析

Analysis for Characteristic Chemicals of Incense of Burning Agarwood from Three Production Zones

【目的】分析沉香主要成分在燃烧过程中的挥发或裂解方式,比较国产、惠安系和星洲系3个产区沉香燃烧释放的挥发性和半挥发性成分组成及差异,确认对沉香燃烧香气有贡献的气味活性化合物及其来源,解释沉香燃烧气味形成原因,为沉香产地识别和香气品质评价提供科学依据。【方法】采用水蒸馏和乙醇提取沉淀方法分离沉香树脂部分中倍半萜类和2-(2-苯乙基)色酮类(PECs)特征成分,应用热重(TG)分析倍半萜类、PECs化合物和木材部分的热质量损失模式,使用静态顶空气相色谱质谱联用(HS-GC-MS)分析不同产区沉香燃烧烟气中的挥发性成分并确认气味活性化合物,利用主成分分析(PCA)分析3个产区沉香燃烧释放的挥发性成分差异,收集燃烧沉香产生的烟尘,运用液相质谱(LC-MS/MS)联用分析其中PECs成分组成,通过HS-GC-MS分析加热后的PECs标准品,探究沉香中PECs化合物裂解机制及其对燃烧气味的影响。【结果】1)沉香中的倍半萜类化合物在200℃以内完全挥发,PECs化合物质量在150~350℃缓慢降低,木材在250℃以上迅速燃烧。2)沉香燃烧释放的挥发性成分主要为芳香族和倍半萜类化合物,其中芳香族化合物种类和含量明显增加,为沉香燃烧气体提供辛、甜、杏仁、花香等丰富的气味;国产沉香中2-甲氧基-4-乙烯基苯酚、3,4-二甲氧基苯酚、乙酰丁香酚等7种化合物释放量与样品乙醇提取物含量负相关,这些化合物主要为沉香燃烧烟气提供烟熏、粉尘和木材气味。3)倍半萜类关键香气化合物桉油烯醇、cis-桉叶-6-烯-11-醇、愈创木醇的相对含量在国产沉香中最高,惠安系沉香中次之,星洲系沉香中最低。4)沉香燃烧烟尘中含有多种Flidersia型2-(2-苯乙基)色酮类(FTPECs)化合物,但未检测到四氢2-(2-苯乙基)色酮类(THPECs)化合物。沉香四醇裂解释放苄基丙酮和苯甲醛,2-(2-苯乙基)色酮高温裂解不仅生成苯甲醛、苯乙醇等6种芳香族化合物,还能挥发进入空气。【结论】沉香的主要成分倍半萜类、PECs化合物和木材燃烧过程中热质量损失模式不同,倍半萜类化合物直接挥发进入空气,PECs化合物和木材裂解生成多种芳香族化合物,这些化合物具有多种气味,对沉香燃烧香气有重要影响。不同产区沉香燃烧后释放的化学成分存在一定差异,星洲系与惠安系和国产沉香差异较大。高温下不同种类PECs裂解生成芳香族化合物种类和含量不同,FTPECs可部分挥发进入空气中。

【Objective】In this study,the releasing or pyrolysis of main components in agarwood were analyzed,volatiles and semi-volatiles released by incense of agarwood from Guan-Xiang Zone,Hoi-An Zone and Sin-Chew Zone were analyzed and compared to identify the odorants and their origins,which explained for the mechanism behind odor formation of agarwood incense and provided references for production zone identification and odor qualification of agarwood.【Method】Sesquiterpenoids and 2-(2-phenylethyl)chromones(PECs)were isolated and purified from agarwood resin respectively by hydro distillation or ethanol extraction and precipitation.Thermo-gravity(TG)loss patterns of sesquiterpenoids,PECs and wood were analyzed by TG.Agarwood from 3 production zones were collected and the burning smoke were collected.The volatiles released by burning agarwood were analyzed and the odorants were identified by static headspace-gas-chromatograph-mass spectrum(HSGC-MS).The PECs in the dust from the smoke were analyzed and preliminarily identified by liquid chromatograph-mass spectrum.The products from different PECs under heating were analyzed and identified by HS-GC-MS.【Result】1)Sesquiterpenoids mostly diffused into air under 200℃,PECs pyrolyzed gradually between 150−350℃and wood burned quickly over 250℃.2)Volatiles released by burning agarwood were mainly aromatic compounds and sesquiterpenoids.Types and quantity of aromatic compounds increased,which enriched the agarwood incense with spicy,sweet,almond and floral odors.The release of 7 chemicals including 2-methoxy-4-vinylphenol 3,4-dimethoxyphenol and aceteugenol decreased along with the increase of ethanol extracts of Guan-Xiang zone agarwood.Those chemicals donated smoke,dusty and wood odors.3)The relative contents of key odor-active compounds such as(-)-spathulenol,cis-eudesm-6-en-11-ol,guaiol were highest in Guan-Xiang Zone agarwood and lowest in Sin-Chew Zone agarwood with Hoi-An Zone agarwood between them.4)PECs in the dust of agarwood smoke were mainly comprised with Flidersia type 2-(2-phenylethyl)(FPECs)chromones and no tetrahydro-2-(2-phenylethyl)chromones(THPECs)were detected.Agarotetrol pyrolyzed into benzylacetone and benzaldehyde,2-(2-Phenylethyl)chromone not only pyrolyzed into 6 aromatic compounds including benzaldehyde and benzyl alcohol,but became volatile under heating.【Conclusion】Sesquiterpenoids,PECs and wood in agarwood maintained different thermo-mass loss patterns.Sesquiterpenoids acted as volatiles while PECs and wood pyrolyzed into aromatic compounds.Both maintain various odor attributes which impacted on the odor of agarwood incense.Incenses of burning agarwood from 3 production zones differed in the volatile compositions.Agarwood from Sin-Chew Zone diverged with those from Guan-Xiang Zone and Hoi-An Zone.The types and quantity of aromatic compounds released by different PECs when heated differed.FTPECs partly became volatile under heating.