Compounds released by sequential chemolysis from cuticular remains of the Cretaceous Gymnosperm Squamastrobus tigrensis (Patagonia, the Argentine)
Compounds released by sequential chemolysis from cuticular remains of the Cretaceous Gymnosperm Squamastrobus tigrensis (Patagonia, the Argentine)
复制标题
DOI：
10.1016/s0146-6380(99)00034-0
复制
发表时间：
1999-01-01
影响因子：
3
通讯作者：
Archangelsky, S
中科院分区：
文献类型：
--
作者：
Almendros, G;Dorado, J;Archangelsky, S
对在巴塔哥尼亚地区发现的白垩纪裸子植物鳞状裸子体角质层遗骸的化学成分进行了分析，其中包括：(I)超声波处理后的脂肪提取；(Ii)BF3-MeOH的进一步酯交换；(Iii)最终残留物的反复温和的NaBO2-H_2O_2降解。在连续处理后释放的化合物组合被认为反映了不同水平的角质层结构中的脂类形态模式。特别是，经过所有处理后，在C-9和C-10具有最大值的一系列同源的α，欧米伽-烷二酸的优势表明了一个基于大分子的聚亚甲基网络；该网络的单元包含链内不饱和或取代，其位置与前体不饱和C-16和C-18酸的位置相似。现存植物的切削素和亚麻黄素的低产量被解释为化石角质层强烈的微生物蚀变和/或成岩转化。结合红外光谱和分析热解的数据，这表明鳞毛虫遗骸由一种大分子烷基混合物组成，其中原始的C主链被去功能化，被重新氧化，并受到新形成的非水解桥的可能贡献而发生额外的缩合。这种缺乏纤维素的材料似乎包括一小部分蚀变木质素，并经历了广泛的氧化，但没有进一步的热蚀变导致脱羧基。这种成岩作用的一个可能结果是，一部分树脂组分转化为低分子量烷基苯和烷基萘，而另一部分凝聚成非常稳定的不可水解性残留物。这种残留物的化学稳定性不是由于芳构化作用，而是由于改变的脂肪族生物大分子的二次缩合。(C)1999爱思唯尔科学有限公司。保留所有权利。
The chemical composition of morphologically well-preserved cuticular remains of the Cretaceous Gymnosperm Squamastrobus tigrensis found in the Bajo Tigre locality (Patagonia) was analysed by a progressive chemical degradation sequence involving: (i) lipid extraction after ultrasonic treatments; (ii) further BF3-MeOH transesterification; and (iii) repeated mild NaBO2-H2O2 degradation of the final residue. The compound assemblages released after the successive treatments were considered to reflect lipid speciation patterns in the different levels of the cuticular structure. In particular, after all the treatments, the dominance of a homologous series of alpha,omega-alkanedioic acids with maxima at C-9 and C-10 indicates a polymethylene network based on macromolecules; the units of this network contain in-chain unsaturations or substitutions in positions similar to those in precursor unsaturated C-16 and C-18 acids. The low yields of omega-hydroxyacids typical of cutins and suberins of extant plants are interpreted as an intense microbial alteration and/or diagenetic transformation of the fossil cuticle.In conjunction with data from infrared spectroscopy and analytical pyrolysis, this suggests that the Squamastrobus remains consist of a macromolecular alkyl mixture in which the original C backbone has been defunctionalized, reoxidized, and subjected to additional condensation by the probable contribution of newly-formed, nonhydrolyzable bridges. It appears that this cellulose-lacking material includes a small moiety of altered lignin, and has been subjected to extensive oxidation, but not to further thermal alteration leading to decarboxylation. A possible result of this diagenetic alteration is that a portion of the resin constituents were transformed into lower molecular weight alkylbenzenes and alkylnaphthalenes, whereas another portion condensed into a very stable, nonhydrolyzable residue. The chemical stability of this residue is not due to aromatization, but to secondary condensation of altered aliphatic biomacromolecules. (C) 1999 Elsevier Science Ltd. All rights reserved.