Mass spectrometry investigation of nucleoside adducts of fatty acid hydroperoxides from oxidation of linolenic and linoleic acids

New insights into the off-flavor improvement of soymilk by three grinding processing: Dry-blanching grinding, wet-blanching grinding, and wet-anaerobic grinding

Advances in grinding strategies have been beneficial to eliminating the off-flavor of soymilk and improving the quality soy products. Herein, four grinding processing, dry-blanching grinding (D-BG), wet-blanching grinding (W-BG), wet-anaerobic grinding (W-AG) and traditional grinding (TG) were employed and found to impose a significant impact on off-flavor components, accompanied by changes of hydroperoxides and free radicals. The results showed that all three methods could significantly hinder the formation of C6 aldehydes. C8 Alcohols and (E)-2-heptenal could be removed by D-BG, but lipids in dehulled soybean were prefer to be oxidized during storage, resulting in the accumulation of hydroperoxides and radicals. W-BG and W-AG have higher levels of 1-octen-3-ol, and soaking at an alkaline pH and increasing the number of rinses is beneficial for its removal. Gas chromatography-olfaction-mass spectrometry (GC-O-MS) combined with sensory evaluation showed that off-flavor profile of d-BGS, W-BGS and W-AGS was different. D-BG and W-AG possessed better flavor quality.

Conjugated linoleic acid (CLA) as a functional food: Is it beneficial or not?

Conjugated linoleic acid (CLA) has attracted great attention in recent years as a popular class of functional food that is broadly used. It refers to a group of geometric and positional isomers of linoleic acid (LA) with a conjugated double bond. The main natural sources of CLA are dairy products, beef and lamb, whereas only trace amounts occur naturally in plant lipids. CLA has been shown to improve various health issues, having effects on obesity, inflammatory, anti-carcinogenicity, atherogenicity, immunomodulation, and osteosynthesis. Also, compared to studies on humans, many animal researches reveal more positive benefits on health. CLA represents a nutritional avenue to improve lifestyle diseases and metabolic syndrome. Most of these effects are attributed to the two major CLA isomers [conjugated linoleic acid cis-9,trans-11 isomer (c9,t11), and conjugated linoleic acid trans-10,cis-12 isomer (t10,c12)], and their mixture (CLA mix). In contrast, adverse effects of CLA have been also reported, such as glucose homeostasis, insulin resistance, hepatic steatosis and induction of colon carcinogenesis in humans, as well as milk fat inhibition in ruminants, lowering chicken productivity, influencing egg quality and altering growth performance in fish. This review article aims to discuss the health benefits of CLA as a nutraceutical supplement and highlight the possible mechanisms of action that may contribute to its outcome. It also outlines the feasible adverse effects of CLA besides summarizing the recent peer-reviewed publications on CLA to ensure its efficacy and safety for proper application in humans.

Widespread occurrence of in-source fragmentation in the analysis of natural compounds by liquid chromatography-electrospray ionization mass spectrometry

RATIONALE

The in-source fragmentation (ISF) of analyte or co-eluting substances produces unintentional fragment ions, which hampers identification and quantification by liquid chromatography-mass spectrometry (LC/MS). Natural compounds derived from plants also contain fragile moieties that may undergo ISF. However, the characteristics of ISF of natural compounds in LC/MS are still unclear.

METHODS

The ISF behavior of 214 natural compounds was assayed in LC with Q/orbitrap MS in electrospray ionization (ESI) mode and the extent of ISF was evaluated.

RESULTS

Up to 82% of tested compounds underwent ISF and half of the tested natural compounds that contain more than one fragile moiety underwent successive and severe ISF to generate serial structurally related ISF products. The major ISF-altering moieties for natural compounds were hydroxyl, lactone, glycosyl and ether, resulting in neutral loss of H₂ O or CO, deglycosylation or cleavage of ether bond, respectively. Some compounds such as terpenoids underwent severe ISF and less than 1% parent form can be observed. For natural compounds, ISF products with similar structures are more likely to cause interference in analysis because the ISF products may share identical mass-to-charge ratio and similar MS² fragmentation patterns with precursor ions of the homologs in plants. Furthermore, severe ISF may cause a false negative in the identification of the parent form.

CONCLUSIONS

In summary, ISF was a highly frequent phenomenon for analysis of natural compounds by LC/ESI-MS, and extensive and successive ISF of natural products may cause misannotation and misidentification with homologs in plants. The study should raise awareness of ISF interference during the analysis of natural compounds.

Comprehensive separation of a wide variety of compounds from olive leaves by counter-current chromatography with three-phase solvent system

The three-phase solvent system counter-current chromatography has been of great research interest, because it can separate compounds with a wide range of polarity. The solvent system of n-hexane/methyl tert-butyl ether/acetonitrile/water (5:5:7:5, v/v) was used for counter-current chromatographic comprehensive separation of olive leaves. The study adopted the normal elution mode. The middle phase and the lower phase (at a volume ratio of 7:3) were pumped into the column simultaneously, followed by eluting with the upper, middle and lower phases in sequence. The retention rate of the stationary phase measured by the experiment was 73.5%. The upper phase was used to eluted the nonpolar compounds, then the mobile phase was switched to the middle phase to elute the moderately hydrophobic compounds, finally, the polar compounds were eluted by the lower phase remaining in the chromatographic column. This method successfully separated eight compounds in one step within 270 minutes and five compounds were identified. The logP values of these five compounds were 7.44, 7.86, 4.16, -0.11, 0.96, respectively, covering a wide range of polarities. The present study demonstrated that the three-phase solvent has a strong extraction capacity for ingredients from extremely hydrophilic compounds to extremely hydrophobic compounds. This article is protected by copyright. All rights reserved.

Native electrospray ionization mass spectrometry combined with molecular docking for the characterization of ginsenoside-myoglobin interactions

RATIONALE

The interactions between proteins and ligands are involved in many biological processes and early stages of drug development. Native electrospray ionization mass spectrometry (native ESI-MS) has played an important role in the characterization of protein-ligand interactions. Herein, native ESI-MS combined with molecular docking was used for the characterization of ginsenoside-myoglobin (Mb) interactions.

METHODS

The binding of ginsenosides (Rb₃ , Rc, Rd, Re) to Mb was determined by native ESI-MS. Titration experiments were performed for the calculation of the dissociation constants (K_d ) of the complexes. Molecular docking was used to simulate the binding of ginsenosides with Mb by AutoDock.

RESULTS

The ginsenoside-Mb complex with stoichiometric ratio 1:1 was observed by native ESI-MS. The K_d values determined by the direct calculation method were matched with those obtained by the curve fitting method. However, the relative standard deviations (RSDs) obtained by direct calculation were larger than those obtained by curve fitting. From the molecular docking, it was inferred that hydrophobic interactions, hydrogen bonding and Van der Waals forces participate in the binding of ginsenosides to proteins.

CONCLUSIONS

The ginsenoside-Mb interactions can be characterized by ESI-MS combined with molecular docking. This approach can be helpful to investigate the interactions between natural drugs and proteins in various diseases.