Application of supercritical fluid chromatography to the analysis of hydrophobic metabolites

Polyphenols: Secondary Metabolites with a Biological Impression

Polyphenols are natural compounds which are plant-based bioactive molecules, and have been the subject of growing interest in recent years. Characterized by multiple varieties, polyphenols are mostly found in fruits and vegetables. Currently, many diseases are waiting for a cure or a solution to reduce their symptoms. However, drug or other chemical strategies have limitations for using a treatment agent or still detection tool of many diseases, and thus researchers still need to investigate preventive or improving treatment. Therefore, it is of interest to elucidate polyphenols, their bioactivity effects, supplementation, and consumption. The disadvantage of polyphenols is that they have a limited bioavailability, although they have multiple beneficial outcomes with their bioactive roles. In this context, several different strategies have been developed to improve bioavailability, particularly liposomal and nanoparticles. As nutrition is one of the most important factors in improving health, the inclusion of plant-based molecules in the daily diet is significant and continues to be enthusiastically researched. Nutrition, which is important for individuals of all ages, is the key to the bioactivity of polyphenols.

Supercritical fluid chromatography-mass spectrometry enables simultaneous measurement of all phosphoinositide regioisomers

Phosphoinositide species, differing in phosphorylation at hydroxyls of the inositol head group, play roles in various cellular events. Despite the importance of phosphoinositides, simultaneous quantification of individual phosphoinositide species is difficult using conventional methods. Here we developed a supercritical fluid chromatography-mass spectrometry method that can quantify the molecular species of all seven phosphoinositide regioisomers. We used this method to analyze (1) profiles of phosphoinositide species in mouse tissues, (2) the effect of lysophosphatidylinositol acyltransferase 1-depletion on phosphoinositide acyl-chain composition in cultured cells, and (3) the molecular species of phosphatidylinositol-3-phosphate produced during the induction of autophagy. Although further improvement is needed for the absolute quantification of minor phosphoinositide regioisomers in biological samples, our method should clarify the physiological and pathological roles of phosphoinositide regioisomers at the molecular species level.

Antioxidant Potential Overviews of Secondary Metabolites (Polyphenols) in Fruits

The rise in consumption of energy-dense foods has resulted in the displacement of several essential dietary gaps, causing numerous long-lasting diseases, including obesity, stroke, hypertension, and several forms of cancer. Epidemiological studies encourage more fruit consumption to prevent these diseases. The defensive mechanisms provided by these fruits against illness are due to the existence of several antioxidants. Recent studies proved that (poly) phenolic compounds are ideally the core phytochemicals with both functional and health-promoting properties found in the plant's kingdom, and low intake could result in the risk of certain diseases. Phytonutrients are powerful antioxidants that can modify metabolic activation and detoxification of carcinogens. The ideal motive of this review is to provide an overview as well as illuminate the polyphenolic merits of fruits in general. Fruits have several merits, including weight maintenance, proper health development, and satiety. There are many analytical methods for determining and measuring the phenolic content of different products. Phenolic compounds are of nutritional interest since they aid in the retardation and inhibition of lipids by acting as scavengers that prevent and protect the proliferation of oxidative chains. Future studies are required to help identify the physiological metabolic activities as well as to improve human health.

Comparison of Retention Behavior between Supercritical Fluid Chromatography and Normal-Phase High-Performance Liquid Chromatography with Various Stationary Phases

The retention behavior of a wide variety of stationary phases was compared in supercritical fluid chromatography (SFC) and normal-phase high-performance liquid chromatography (NP-HPLC). We also attempted to elucidate the retention behavior in SFC by investigating the selectivity of the different stationary phases. SFC separation conditions with polar stationary phases, such as silica gel (SL) and diol (Diol) phases, operate via adsorptions that include hydrophilic and ionic interactions similar to those in NP-HPLC. Moreover, non-polar stationary phases, such as pentabromophenyl (PBr), pyrenylethyl (PYE), and octadecyl (C₁₈), could be used despite the non-polar mobile phase conditions, because the dispersion and π-π interactions were stronger in SFC than in HPLC. These results reflect the selectivity of the stationary phase and its retention factor, thus providing useful information for the selection of appropriate stationary phases for particular analytes.

Quantitative determination of major alkaloids in Cinchona bark by Supercritical Fluid Chromatography

Chinoline alkaloids found in Cinchona bark still play an important role in medicine, for example as antimalarial and antiarrhythmic drugs. For the first time Supercritical Fluid Chromatography has been utilized for their separation. Six respective derivatives (dihydroquinidine, dihydroquinine, quinidine, quinine, cinchonine and cinchonidine) could be resolved in less than 7 min, and three of them quantified in crude plant extracts. The optimum stationary phase showed to be an Acquity UPC² Torus DEA 1.7 μm column, the mobile phase comprised of CO₂, acetonitrile, methanol and diethylamine. Method validation confirmed that the procedure is selective, accurate (recovery rates from 97.2% to 103.7%), precise (intra-day ≤2.2%, inter-day ≤3.0%) and linear (R² ≥ 0.999); at 275 nm the observed detection limits were always below 2.5 μg/ml. In all of the samples analyzed cinchonine dominated (1.87%-2.30%), followed by quinine and cinchonidine. Their total content ranged from 4.75% to 5.20%. These values are in good agreement with published data, so that due to unmatched speed and environmental friendly character SFC is definitely an excellent alternative for the analysis of these important natural products.

Supercritical fluid chromatography for lipid analysis in foodstuffs

The task of lipid analysis has always challenged separation scientists, and new techniques in chromatography were often developed for the separation of lipids; however, no single technique or methodology is yet capable of affording a comprehensive screening of all lipid species and classes. This review acquaints the role of supercritical fluid chromatography within the field of lipid analysis, from the early developed capillary separations based on pure CO₂ , to the most recent techniques employing packed columns under subcritical conditions, including the niche multidimensional techniques using supercritical fluids in at least one of the separation dimensions. A short history of supercritical fluid chromatography will be introduced first, from its early popularity in the late 1980s, to the sudden fall and oblivion until the last decade, experiencing a regain of interest within the chromatographic community. Afterwards, the subject of lipid nomenclature and classification will be briefly dealt with, before discussing the main applications of supercritical fluid chromatography for food analysis, according to the specific class of lipids.

Chromatographic behavior of small organic compounds in low-temperature high-performance liquid chromatography using liquid carbon dioxide as the mobile phase

Low-temperature high-performance liquid chromatography, in which a loop injector, column, and detection cell were refrigerated at -35ºC, using liquid carbon dioxide as the mobile phase was developed. Small organic compounds (polyaromatic hydrocarbons, alkylbenzenes, and quinones) were separated by low-temperature high-performance liquid chromatography at temperatures from -35 to -5ºC. The combination of liquid carbon dioxide mobile phase with an octadecyl-silica (C18 ) column provided reversed phase mode separation, and a bare silica-gel column resulted in normal phase mode separation. In both the cases, nonlinear behavior at approximately -15ºC was found in the relationship between the temperature and the retention factors of the analytes (van't Hoff plots). In contrast to general trends in high-performance liquid chromatography, the decrease in temperature enhanced the separation efficiency of both the columns.

Supercritical fluid chromatography for the separation of isoflavones

The first protocol for the analysis of isoflavones by supercritical fluid chromatography is reported. Optimum results were obtained on an Acquity UPC(2) BEH 1.7 μm column, using a solvent gradient of supercritical carbon dioxide and methanol (with phosphoric acid as additive) for elution. The method enables the baseline separation of nine isoflavones (aglyca and glycosides) in 8 min, and is suitable for their quantitative determination in dietary supplements containing soy (Glycine max), red glover (Trifolium pratense) and kudzu (Pueraria lobata). Method validation confirmed that the assay is selective, linear (R(2)≥0.9994), accurate (recovery rates from 97.6 to 102.4%), as well as precise on the short- and long-term level (intra-day precision ≤2.1%), and shows an on-column detection limit of 0.2 ng and below. This, together with an excellent performance shown in the analysis of real samples, indicates that SFC is well suited for the fast and accurate determination of isoflavones in complex matrices. Disadvantages compared to the established approaches were not observed, so that SFC has to be considered in this case as an (at least) equivalent analytical alternative.

Techniques for analysis of plant phenolic compounds

Phenolic compounds are well-known phytochemicals found in all plants. They consist of simple phenols, benzoic and cinnamic acid, coumarins, tannins, lignins, lignans and flavonoids. Substantial developments in research focused on the extraction, identification and quantification of phenolic compounds as medicinal and/or dietary molecules have occurred over the last 25 years. Organic solvent extraction is the main method used to extract phenolics. Chemical procedures are used to detect the presence of total phenolics, while spectrophotometric and chromatographic techniques are utilized to identify and quantify individual phenolic compounds. This review addresses the application of different methodologies utilized in the analysis of phenolic compounds in plant-based products, including recent technical developments in the quantification of phenolics.

Fast separation of triterpenoids by supercritical fluid chromatography/evaporative light scattering detector

The screening of plant material, the chemical composition, the abundance and the biological activity of triterpenoids are of a major economical importance. The classical analytical methods, such as TLC, GC, and HPLC are either little resolutive, or require derivatization steps, or fail in sensitivity. The supercritical fluid chromatography/evaporative light scattering detector (SFC/ELSD) coupling provides high resolution, fast analysis and higher responses for the analysis of triterpenoids. After the initial screening of seven stationary phases to select the well suited one, analytical conditions (modifier percentage, from 10 to 3%; backpressure (from 12 to 18 MPa) and temperature (from 15 to 25 °C) were studied to improve the separation, and ELSD detection of a standard mixture composed of 8 triterpenoids (oleanolic acid, erythrodiol, β-amyrin, ursolic acid, uvaol, betulinic acid, betulin, lupeol). Applied to apple pomace extracts, this method allows the separation of about 15 triterpenoid compounds, in less than 20 min, with isocratic conditions. Moreover, the ELSD response is dramatically higher than the one provided by UV detection, and avoids derivatization steps. An attempt to identify some compounds was done by collecting chromatographic peaks and further analyzing them with mass spectrometry. Complete identification or molecular formula could be proposed for 11 compounds. However, due to the presence of position and orientation isomers the absolute identification remains difficult, despite some retention rules deduced from the standard analysis.

Application of supercritical fluid carbon dioxide to the extraction and analysis of lipids

Supercritical carbon dioxide (SCCO2) is an ecofriendly supercritical fluid that is chemically inert, nontoxic, noninflammable and nonpolluting. As a green material, SCCO2 has desirable properties such as high density, low viscosity and high diffusivity that make it suitable for use as a solvent in supercritical fluid extraction, an effective and environment-friendly analytical method, and as a mobile phase for supercritical fluid chromatography, which facilitates high-throughput, high-resolution analysis. Furthermore, the low polarity of SCCO2 is suitable for the extraction and analysis of hydrophobic compounds. The growing concern surrounding environmental pollution has triggered the development of green analysis methods based on the use of SCCO2 in various laboratories and industries. SCCO2 is becoming an effective alternative to conventional organic solvents. In this review, the usefulness of SCCO2 in supercritical fluid extraction and supercritical fluid chromatography for the extraction and analysis of lipids is described.

Metabolic profiling of lipids by supercritical fluid chromatography/mass spectrometry

This review describes the usefulness of supercritical fluid chromatography (SFC) for the metabolic profiling of lipids. First, non-targeted lipid profiling by SFC/MS is described. The use of SFC/MS allows for high-throughput, exhaustive analysis of diverse lipids, and hence, this technique finds potential applications in lipidomics. Development of a polar lipid profiling method with trimethylsilyl (TMS) derivatization widens the scope of applicability of SFC/MS. SFC is a high-resolution technique that is suitable for non-targeted profiling aimed at the simultaneous analysis of many components. Next, targeted lipid profiling by SFC/MS is described. SFC is useful for the separation of lipids, such as carotenoids and triacylglycerols, which have numerous analogs with similar structures. In addition, SFC/MS shows the maximum efficiency for the target analysis of lipids in a biological sample that includes many matrices. Finally, a high-resolution, high-throughput analytical system based on SFC/MS is stated to be suitable for lipidomics because it is useful not only for the screening of lipid mixtures (as a fingerprint method) but also for the detailed profiling of individual components.

Application of supercritical fluid chromatography/mass spectrometry to lipid profiling of soybean

A metabolomics technology for lipid profiling based on supercritical fluid chromatography (SFC) coupled with mass spectrometry (MS) was applied to analyze lipids of soybean. Principal component analysis (PCA) was used to discriminate twelve soybean cultivars according to their suitability for different processed foods such as natto, tofu, edamame, and nimame. By PCA assay, triacylglycerol (TAG) was found as the main variable for discrimination of soybean cultivars. Therefore, a high-throughput and high-resolution TAG profiling method by SFC/MS was developed to more effective discrimination. By investigating several columns, three Chromolith Performance RP-18e columns connected in series were chosen as the most effective column for TAG profiling. Diverse TAGs were separated effectively for 8 min without purification. Additionally, each TAG was identified successfully by the programmed cone voltage fragmentation even without MS/MS analysis and any standard sample.