Resolving phytosterols in microalgae using offline two-dimensional reversed phase liquid chromatography-supercritical fluid chromatography coupled with quadrupole time-of-flight mass spectrometry.

Sterols are unsaponifiable lipids resulting from plant metabolism that exhibit interesting bioactive properties. Microalgae are a major source of specific phytosterols, most of which are still not fully characterized. The similarity in sterol structures and the existence of positional isomers make the separation of phytosterols challenging. A method was developed based on an offline two-dimensional (2D) system, reversed-phase liquid chromatography (RPLC)-supercritical fluid chromatography (SFC)/quadrupole time-of-flight (Q-ToF) mass spectrometry, for the identification of sterols in microalgae. Subsequent positive-mode MS/MS was used to confirm the identified phytosterols. The 2D chromatogram exhibited a pattern related to the positions of the double bonds, which were confirmed by standard injection, enabling structural elucidation. The analysis of the unsaponifiable fraction of two algae, namely Scenedesmus obliquus, a freshwater microalgae, and Padina pavonica, a marine macroalgae, highlighted the ability of the method to distinguish a large number of sterol isomers.

Off-line two-dimensional liquid chromatography separation for the quality control of saponins samples from Quillaja Saponaria.

Quil-A is a purified extract of saponins with strong immunoadjuvant activity. While specific molecules have been identified and tested in clinical trials, Quil-A is mostly used as a totum of the Quillaja Saponaria bark extract. Quality control of the extract stability is usually based on the monitoring of specific saponins, whereas the comparison of samples with an initial chromatogram seems more appropriate. A reference fingerprint based on comprehensive two-dimensional liquid chromatography offers a rapid detection of nonconform samples. To fulfill quality control constraints, off-line configuration using basic instrumentation was promoted. Hence, reversed-phase liquid chromatography × reversed-phase liquid chromatography and hydrophilic interaction chromatography × reversed-phase liquid chromatography methods with ultraviolet and single-quadrupole mass spectrometry detection were kinetically optimized. The reversed-phase liquid chromatography × reversed-phase liquid chromatography method used a pH switch between dimensions to maximize orthogonality. Despite diagonalization, it led to a high peak capacity of 831 in 2 h. On the other hand, the combination of hydrophilic interaction chromatography and reversed-phase liquid chromatography offered a larger orthogonality but a lower, yet satisfactory peak capacity of 673. The advantages of both methods were illustrated on degraded samples, where the reversed-phase liquid chromatography × reversed-phase liquid chromatography contour plot highlighted the loss of fatty acid chains, while the hydrophilic interaction chromatography × reversed-phase liquid chromatography method was found useful to evidence enzymatic loss of sugar moieties.

Biochemical Characterization of the α-l-Rhamnosidase DtRha from Dictyoglomus thermophilum: Application to the Selective Derhamnosylation of Natural Flavonoids.

α-l-Rhamnosidases are catalysts of industrial tremendous interest, but their uses are still somewhat limited by their poor thermal stabilities and selectivities. The thermophilic DtRha from Dictyoglomus thermophilum was cloned, and the recombinant protein was easily purified to homogeneity to afford 4.5 mg/L culture of biocatalyst. Michaelis-Menten parameters demonstrated it to be fully specific for α-l-rhamnose. Most significantly, DtRha demonstrated to have a stronger preference for α(1 → 2) linkage rather than α(1 → 6) linkage when removing rhamnosyl moiety from natural flavonoids. This selectivity was fully explained by the difference of binding of the corresponding substrates in the active site of the protein.

Two-dimensional multi-heart cutting centrifugal partition chromatography-liquid chromatography for the preparative isolation of antioxidants from Edelweiss plant.

The Edelweiss plant has been recognized as a very valuable source of anti-aging principles due to its composition of antioxidants compounds: leontopodic acid A and 3,5-dicaffeoylquinic acid. In this work, off-line multi-heart cutting CPC-LC separation was set up at industrial scale in order to isolate and produce new high quality reference material of these two antioxidants from Edelweiss. For this purpose, CPC and HPLC methods were developed and optimized at laboratory scale and a comprehensive CPCxHPLC analysis of the crude extract was established. Thereby, the CPC method led to a first separation of the target compounds according to their partition coefficient in the solvent system and the HPLC method was performed on the recovered fractions to lead to a second separation. A 2D CPCxHPLC plot was established in order to know the fractions to select at the industrial scale. Then, the CPC and HPLC methods were transferred at industrial scale and the multi-heart cutting CPC-LC was performed in off-line mode. Using CPC with methyl ter-butyl ether-water 1:1 (v/v) solvent system and LC with Denali C18 column, 2g of crude extract sample were injected and leontopodic acid A and 3,5-dicaffeoylquinic acid were recovered with purity over 97%. The compounds were identified by MS and NMR.