The function of pressure for coalification is a long-term controversial issue, and the main cause is that the strata pressure and the tectonic stress were confused, which are two different actions of "pressure". The former benefits the physical coalification but retards the chemical coalification, whereas the latter may not only affect the physical structure of coal but also promote its chemical composition changes. In accordance with the organic molecule evolution of coal, there are two kinds of basic mechanisms of the influence of the tectonic stress on the chemical coalification: the tectonic stress degradation and the tectonic stress polycondensation. The stress degradation mechanism is a process of that, when the tectonic stress acted on the large molecule of coal in the form of mechanical force or kinetic energy, some chemical bonds of low decomposed energy, such as aliphatic side-chain and oxygenic functional groups, were broken up and then were degraded into free radicals of less molecular weight, and finally escaped from coal in the form of liquid organic matter (hydrocarbon). The stress polycondensation is considered that, under the control of the anisotropic tectonic stress, the condensed aromatic nucleus trend to be parallel arranged and to be enhanced through rotating or displacing of aromatic rings, the basic structural unit of coal (BSU) increases by directional development and preferential stack. X-ray diffraction (XRD), Fourier transformation infrared microspectroscopy (FTIR), and rock pyrolysis analysis (Rock-eval) were employed to study the deformed coal series and the non-deformed coal series. The results showed that, compared with the non-deformed coal, the deformed coal exhibits particular characteristics: weaker aliphatic absorbance peak and stronger aromatic absorbance peak, lower pyrolysed hydrocarbon yield, and more increscent BSU. The concepts of stress degradation mechanism and stress polycondensation mechanism presented here would not deny the dominant function of the temperature in coalification, but emphasize the "catalysis" of the tectonic stress in coalification.coalification, pressure factor, tectonic stress degradation, tectonic stress polycondensation, tectonically deformed coal Coal, a kind of organic rock, is very sensitive to geological environment factors, such as temperature, pressure, etc. Various tectonic-thermal events during the geological evolution process would lead to coal producing a series of physical, chemical, structural, and tectonic changes. The research of coalification factors is one of the basic works for coal resources evaluation, coalbed methane development and coal-mining gas prevention [1,2] . Organic macro-molecules in coal is composed of condensed aromatic nucleus of a plenty of side chains and functional groups [3] . They belong to non-crystal state materials that are lack of order in a long distance while better ordered in a short distance [4] . Coalification is a process of rich
Cultivation of the fungal strain Eurotium rubrum, an endophytic fungus that was isolated from the inner tissue of stems of the mangrove plant Hibiscus tiliaceus, resulted in the isolation of two new dioxopiperazine derivatives, namely, dehydrovariecolorin L (1) and dehydroechinulin (2), together with eight known dioxopiperazine compounds including variecolorin L (3), echinulin (4), isoechinulin A (5), dihydroxyisoechinulin A (6), preechinulin (7), neoechinulin A (8), neoechinulin E (9), and cryptoechinuline D (10). The structures of the isolated compounds were determined by extensive analysis of their spectroscopic data as well as by comparison with literature. Compounds 1, 2, 9, and 10 were investigated for their a,a-diphenyl-b-picrylhydrazyl (DPPH) radical-scavenging activity. In addition, the new compounds, 1 and 2, were evaluated for their cytotoxic activity against the P-388, HL-60, and A549 cell lines.Introduction. -A number of tryptophan-derived alkaloids, characterized by a reversed isoprenic chain in the C(2) position of the indole and a 2,5-dioxopiperazine moiety, have been isolated from the genus Aspergillus [1 -5]. These metabolites are of interest because of their activity in various pharmacological assay systems [6]. The genus Eurotium is the teleomorphs of Aspergillus, and is also a common source of tryptophan-derived alkaloids, i.e., echinulins and neoechinulins [7].This article describes the isolation, structure elucidation, and biological activity of two new dioxopiperazine derivatives (1 and 2) from the endophytic fungal strain Eurotium rubrum which was isolated from the inner tissue of stems of the marine mangrove plant Hibiscus tiliaceus. In addition, eight known dioxopiperazine derivatives, including variecolorin L (3) [8], echinulin (4) [9], isoechinulin A (5) [10], dihydroxyisoechinulin A (6) [4], preechinulin (7) [11], neoechinulin A (8) [12], neoechinulin E (9) [12], and cryptoechinuline D (10) [13], were also isolated and identified. It deserves to be mentioned that just at the time when we started to prepare this manuscript, compound 3 was reported as a new metabolite of Aspergillus variecolor B-17, a halotolerant fungal strain isolated from a sediment collection of a salt field in inner Mongolia, China [8].
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