松花粉热降解甾族分子生物标志化合物及其热演化特征

Characteristics and Thermal Evolvution of the Steroid Biomarkers from Pyrolysis of Pine Pollens

松花粉热模拟实验饱和烃馏分中检出大量的甾族系列生物标志化合物,包括甾烯酮、甾烯、规则甾烷、异构化甾烷、重排甾烷、4-甲基甾烷及孕甾烷,芳烃馏分中还检出芳构化甾烷,从而提供了该类生物标志物植物花粉来源的直接证据.甾族化合物模拟温度150℃时开始断裂出来,250～350℃时达到排出高峰,400℃时含量急剧下降,500℃以后因强烈地热降解而无法检出. 250℃模拟样品中的甾族化合物以甾烯丰度最高,还检出了大量的甾烯酮和规则甾烷.它们都是以C29和C28两个碳数为主,且表现出C29>>C28的特点,每个碳数均以ααα20(R+S)两种构型成对出现和相对丰度20R>20S为主要特征.300℃样品中检出C29重排甾烯,350℃时甾烯被大量还原,达到规则甾烷形成的高峰.400℃以后的样品除检出ααα(20R+20S)构型的生物甾烷外,αββ构型异构化甾烷可明显检出,而且也可检出相对丰度较高的C29和C28αβ重排甾烷.规则甾烷的ααα20R构型向20S构型的转化,也随热模拟温度的升高逐渐增强.450℃和500℃的高温模拟样品中检出了较明显的孕甾烷和甲基孕甾烷C21和C22.此外,松粉低温热模拟样品的芳烃馏份中检出单、三芳甾烷.

A large number of steroid compounds were identified by GC-MS analyses from the saturated fractions of thermal simulation samples of pine pollens. They are sterenone,sterene,sterane,iso-sterane,dia-sterane,4-methyl-sterane and pragnane,and aromatic sterane were identified from the aromatic fractions. Consequently, the direct evidence for steroid biologic biomarkers of originating from plant pollens in organic deposit were provided. Steroid compounds begin to appear by the cracking at 150℃ thermal simulation. The expulsion peak stage is from 250℃ to 350℃,and at 400℃ the content of steroid compounds decreases sharply. Steroid biomarkers can not be examined because of strong pyrolysis at the higher temperature stage over 500℃. The sterene is of a highest relative abundance among steroid compounds in the simulation sample at 250℃. Plentiful sterenone and sterane also were identified in the sample,and main carbon numbers are C 28 and C 29. Sterenone,sterene and sterane show the characteristics originating from higher plant and the content of C 29 is much higher than C 28 without exception . All carbon numbers take ααα20(R+S) two constructure and 20R is higher than 20S. Rearrange sterenes were identified in the sample at 300℃. Expulsion peak of steranes occur at 350℃ as a result of the intense deoxidization of sterenes. Relatively abundent C 29 and C 28αβ dia-steranes can be evidently identified besides ααα(20R+20S) biologic model steranes and αββ model iso-steranes in the samples over 400℃. The transformation of steranes from ααα20R model to 20S model gradually intensify along with the rising of thermal simulation temperature. C 21 pragnane and C 22 methyl pargnane were identified in the high temperature simulation samples at 450℃ and 500℃ and they are of clear distinctive characteristics. Moreover, ring A ,ring C aromatic sterane and ring A,B,C aromatic sterane were identified from the low temperature aromatic fractions of thermal simulation of pine pollens.