Speciation and molecular characterization of thiophenic and sulfide compounds in petroleum by sulfonation and methylation followed by electrospray mass spectrometry.

Thiophenes and sulfides are the dominant sulfur-containing compounds in petroleum and have been widely of concern in the fields of petroleum refining and geochemistry. In this study, a novel approach was developed for selective separation and characterization of petroleum-derived thiophenic and sulfide compounds. Thiophenic compounds were selectively converted to sulfonates in the presence of vitriolic acid and can be characterized by negative ion electrospray mass spectrometry. Thiophenic sulfonates were further separated from the oil by silica chromatography and enabled the molecular characterization of sulfides in the residual oil. Various model sulfur compounds and a vacuum gas oil were used to validate the method; thiophenic and sulfide biomarker compounds in a well-documented crude oil were selectively characterized. The results indicate that the approach is feasible for molecular characterization of thiophenic and sulfide compounds, which is complementary to recently developed methods for separation and/or ionization of sulfur compounds in petroleum.

ß­elemene inhibits oxygen­induced retinal neovascularization via promoting miR­27a and reducing VEGF expression.

The present study aimed to investigate the significant role of ß-elemene in mouse models of oxygen-induced retinopathy (OIR). C57BL/6J neonatal mice were used to establish OIR models. They were divided into four groups: Normoxia, OIR, OIR control and OIR­treated. Mice in the OIR group were exposed to 75±5% oxygen for 5 days and returned to a normal oxygen environment on postnatal day 12 (P12). The OIR treated group was intravitreally injected with 1 µl ß­elemene on P12 and subsequently returned to a normal oxygen environment for 5 days (P12­P17). Retinas were obtained on P17. Retinal neovascularization (RNV) was detected using adenosine diphosphatase staining and analyzed by counting the nuclei of neovascular endothelial cells. Vascular endothelial growth factor (VEGF) expression was determined by reverse transcription­quantitative polymerase chain reaction, immunohistochemistry and western blot analysis. MicroRNA (miRNA/miR) microarrays were used to screen out differentially expressed miRNAs between the OIR and ß­elemene­treated groups. Binding the 3'­untranslated region (UTR) of VEGF and miR­27a was confirmed using luciferase assays. It was found that high oxygen concentrations accelerated RNV and increased the number of preretinal neovascular cells; ß­elemene treatment reduced these effects. VEGF mRNA and protein expression was higher in the OIR and OIR control groups, compared with the normoxia and OIR­treated groups. Further, it was shown that miR­22, miR­181a­1, miR­335­5p, miR­669n, miR­190b, miR­27a and miR­93 were upregulated in the OIR­treated group, and downregulated in the OIR group. The prediction websites TargetScan and miRanda revealed that VEGF contained a potential miR­27a binding site in its 3'­untranslated region (UTR). Luciferase assays demonstrated that miR­27a directly bound to the 3'­UTR of VEGF. In vitro experiments demonstrated that miR­27a inhibited VEGF expression. In addition, ß­elemene treatment upregulate miR­27a expression in vivo and in vitro. When miR­27a expression was depleted by miR­27a inhibitor, the protective effect of ß­elemene on RNV was eliminated. The present study demonstrated that ß­elemene reduced RNV in mouse OIR models via miR­27a upregulation, leading to reduced VEGF expression. This finding may contribute to the development of novel therapeutic strategies for human retinopathy.