[Development progress of stationary phase for supercritical fluid chromatography and related application in natural products].

Supercritical fluid chromatography (SFC) is an environment-friendly and efficient column chromatography technology that was developed to expand the application range of high performance liquid chromatography (HPLC) using a supercritical fluid as the mobile phase. A supercritical fluid has a temperature and pressure that are above the critical values as well as relatively dynamic characteristics that are between those of a gas and liquid. Supercritical fluids combine the advantages of high solubility and diffusion, as their diffusion and viscosity coefficients are equivalent to those of a gas, while maintaining a density that is comparable with that of a liquid. Owing to the remarkable compressibility of supercritical fluids, analyte retention in SFC is significantly influenced by the density of the mobile phase. Thus, the column temperature and back pressure are crucial variables that regulate analyte retention in SFC. Increasing the back pressure can increase the density and solubility of the mobile phase, leading to reductions in retention time. The column temperature can affect selectivity and retention, and the degree to which different analytes are affected by this property varies. On the one hand, increasing the temperature reduces the density of the mobile phase, thereby extending the retention time of the analytes; on the other hand, it can also increase the energy of molecules, leading to a shorter retention time of the analyte on the stationary phase. CO2, the most widely employed supercritical fluid to date, presents moderate critical conditions and, more importantly, is miscible with a variety of polar organic solvents, including small quantities of water. In comparison with the mobile phases used in normal-phase liquid chromatography (NPLC) and reversed-phase liquid chromatography (RPLC), the mobile phase for SFC has a polarity that can be extended over a wide range on account of its extensive miscibility. The compatibility of the mobile phase determines the diversity of the stationary phase. Nearly all stationary phases for HPLC, including the nonpolar stationary phases commonly used for RPLC and the polar stationary phases commonly used for NPLC, can be applied to SFC. Because all stationary phases can use the same mobile-phase composition, chromatographic columns with completely different polarities can be employed in SFC. The selectivity of SFC has been effectively expanded, and the technique can be used for the separation of diverse analytes ranging from lipid compounds to polar compounds such as flavonoids, saponins, and peptides. The choice of stationary phase has a great impact on the separation effect of analytes in SFC. As new stationary phases for HPLC are constantly investigated, specialized stationary phases for SFC have also been continuously developed. Researchers have discovered that polar stationary phases containing nitrogen heterocycles such as 2-EP and PIC are highly suitable for SFC because they can effectively manage the peak shape of alkaline compounds and provide good selectivity in separating acidic and neutral compounds.The development of various stationary phases has promoted the applications of SFC in numerous fields such as pharmaceuticals, food production, environmental protection, and natural products. In particular, natural products have specific active skeletons, multiple active groups, and excellent biological activity; hence, these materials can provide many new opportunities for the discovery of novel drugs. According to reports, compounds related to natural products account for 80% of all commercial drugs. However, natural products are among the most challenging compounds to separate because of their complex composition and low concentration of active ingredients. Thus, superior chromatographic methods are required to enable the qualitative and quantitative analysis of natural products. Thanks to technological improvements and a good theoretical framework, the benefits of SFC are gradually becoming more apparent, and its use in separating natural products is expanding. Indeed, in the past 50 years, SFC has developed into a widely used and efficient separation technology. This article provides a brief overview of the characteristics, advantages, and development process of SFC; reviews the available SFC stationary phases and their applications in natural products over the last decade; and discusses prospects on the future development of SFC.

SIRT5 promotes non-small cell lung cancer progression by reducing FABP4 acetylation level.

This study evaluates the role of SIRT5 in non-small cell lung cancer (NSCLC) progression and explores the underlying mechanism. The expression and correlation of SIRT5 and FABP4 in lung cancer were analyzed by the GEPIA database. The expression levels of SIRT5 and FABP4 in NSCLC cells were measured by qRT-PCR and western blot. The effect of SIRT5 and FABP4 on NSCLC cell development was determined. The interaction between SIRT5 and FABP4 was analyzed by co-immunoprecipitation (Co-IP). Tumor mass and volume were measured in nude mice to study the effect on the growth of NSCLC transplanted tumors. GEPIA database analysis showed that SIRT5 was highly expressed, while FABP4 was lowly expressed in lung cancer, which was consistent with the detection results of SIRT5 and FABP4 expressions in NSCLC cell lines. The expression of SIRT5 was negatively correlated with FABP4. Transfection of sh-SIRT5 in NSCLC cells led to a decrease in NSCLC cell malignancy, which was counteracted by sh-FABP4 transfection. Western blot and Co-IP showed that SIRT5 reduced FABP4 expression by inducting the deacetylation of FABP4. Nude mice in the sh-SIRT5 + sh-FABP4 group had significantly reduced tumor mass and volume compared with those in the sh-FABP4 group, while the tumor mass and volume in the sh-SIRT5 + sh-FABP4 group were increased in comparison to those in the sh-SIRT5 group. To conclude, collected evidence showed that SIRT5 promoted NSCLC cell development by reducing FABP4 acetylation level.