The aim of the present study was to examine changes in phenolic compounds during refining of rapeseed oil. In crude rapeseed oil, 4-vinylsyringol (canolol) is the dominant phenolic compound, ...accounting for 85% of total phenolics. Refining decreased the total amount of phenolic compounds by 90%. NMR and MS analyses of edible rapeseed oil phenolic extracts identified 4-vinylsyringol dimer as the dominant phenolic compound. This phenolic compound appears to form through acid-catalyzed dimerization-aromatic substitution of 4-vinylsyringol monomers. Analysis of rapeseed oils from different stages of the refining process suggest that 4-vinylsyringol dimer forms during the neutralization phase, when H3PO4 acts as a catalyst, or during bleaching, when acid-activated bleaching earth acts as the catalyst. Whether 4-vinylsyringol forms during one or the other phase appears to depend on the phospholipid content of the crude oil. These insights may be useful for designing rapeseed oil refining processes that maximize levels of 4-vinylsyringol dimer.
•4-Vinylguaiacol (4-VQ) and 4-vinylsyringol (4-VS) were added to stabilize oils.•4-VQ was more effective antioxidant than 4-VS.•Induction period (IP) increase was the lowest for olive oil and the ...highest for flaxseed oil.•4-VQ in similar degree affected IP of refined and cold-pressed rapeseed oil.
The aim of the work is to compare the antioxidant activity of 4-vinylguaiacol (4-VQ) and 4-vinylsyringol (4-VS) added to stabilize three (flaxseed, olive and rapeseed) commercial oils. The phenolics were added at concentration of 20, 40 and 80mg per 100g of oil. The oils were oxidized in a Rancimat test at 110°C. The linear dependences between the concentrations of each of these compounds and the induction period (IP) were found. Generally, 4-VQ was more effective, since the determined IP increase after its addition was from 5 to 25-fold higher than for the same addition of 4-VS. The highest increase was noted for flaxseed oil, for which 80mg 4-VQ addition per 100g of oil resulted in 50% IP increase. The highest absolute values of IP were reached by extra virgin olive oil, naturally abundant in phenolic compounds and with the lowest fatty acids oxidation index.
Sinapine (sinapoylcholine) is an antinutritive phenolic compound that can account for up to 2% of seed weight in brassicaceous oilseed crops and reduces the suitability of their protein-rich seed ...meal for use as animal feed. Sinapine biosynthesis draws on hydroxycinnamic acid precursors produced by the phenylpropanoid pathway. The 4-vinyl derivatives of several hydroxycinnamic acids have industrial applications. For example, 4-vinyl phenol (4-hydroxystyrene) is a building block for a range of synthetic polymers applied in resins, inks, elastomers, and coatings. Here we have expressed a modified bacterial phenolic acid decarboxylase (PAD) in developing seed of Camelina sativa to redirect phenylpropanoid pathway flux from sinapine biosynthesis to the production of 4-vinyl phenols. PAD expression led to a ∼95% reduction in sinapine content in seeds of both glasshouse and field grown C. sativa and to an accumulation of 4-vinyl derivatives of hydroxycinnamic acids, primarily as glycosides. The most prevalent aglycone was 4-vinyl phenol, but 4-vinyl guaiacol, 6-hydroxy-4-vinyl guaiacol and 4-vinylsyringol (Canolol) were also detected. The molar quantity of 4-vinyl phenol glycosides was more than twice that of sinapine in wild type seeds. PAD expression was not associated with an adverse effect on seed yield, harvest index, seed morphology, storage oil content or germination in either glasshouse or field experiments. Our data show that expression of PAD in brassicaceous oilseeds can supress sinapine accumulation, diverting phenylpropanoid pathway flux into 4-vinyl phenol derivatives, thereby also providing a non-petrochemical source of this class of industrial chemicals.
•A phenolic acid decarboxylase was expressed in developing Camelina sativa seeds.•Production of the antinutritive phenolic compound sinapine was reduced by 95%.•Hydroxycinnamic acids were converted to 4-vinyl phenols and accumulated as glycosides.•The quantity of 4-vinyl phenols was more than twice that of sinapine in wild type.•Seed yield appeared not to be affected in either glasshouse or field experiments.
► 4-Vinyl derivatives were prepared by thermal decarboxylation of hydroxycinnamic acids. ► Their antioxidant properties were determined under various conditions for the first time. ► Decarboxylation ...lowered reducing and radical-scavenging capacities of phenolic acids. ► In emulsion derivatives were better antioxidants than phenolic acids. ► Antioxidant activity of compounds in emulsion is mostly defined by their partition.
The compounds 4-vinylphenol (4-VP), 4-vinylguaiacol (4-VG), 4-vinylsyringol (4-VS) and 4-vinylcatechol (4-VC) were prepared by thermal decarboxylation of the corresponding hydroxycinnamic acids p-coumaric, ferulic, sinapic and caffeic acid, respectively. For confirmation of the synthesised products LC–MS followed by NMR analysis was used. To evaluate their antioxidant potential, their reducing power and efficiency in scavenging the alkylperoxyl radical generated in an emulsion system, the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical and the superoxide anion radical (O2-) were determined. All tested 4-vinyl derivatives revealed weaker antioxidant activity in a homogeneous polar medium than the corresponding phenolic acids. In the emulsion system the activity for 4-vinyl derivatives was higher than was the activity of their corresponding phenolic acids, with 4-VG as the most active among the tested phenolic compounds.
4-Vinylsyringol, also referred to as canolol, is a highly active antioxidant and potent lipidperoxyl radical scavenger found in rapeseed. The canolol content of rapeseed can be increased through the ...decarboxylation of sinapic acid via roasting treatments. Different roasting conditions were tested and compared and an optimum for the canolol formation was found at 160
°C. The canolol content of the rapeseed samples with optimal roasting increased by a factor of 120 in relation to the unroasted sample. The rapeseed was ground, extracted and analysed by normal-phase HPLC/UV. The structure of canolol was confirmed by NMR and MS techniques. Several rapeseed oils were purchased in German food stores and analysed. No differences in canolol content were observed in both cold-pressed and rape kernel oil samples tested. Dehulled rapeseed samples demonstrated no significant difference in canolol content when compared to unpeeled rapeseed samples.
Different phenolic compounds were identified in commercial rapeseed oils, as well as in a commercial by-product of oil refining, the deodistillate. Reversed-phase HPLC analysis and the successive ...fragmentation procedure by ESI-MS
n
(electrospray ionisation mass spectrometry) showed a significant fragmentation pattern for new compounds, the
cis- and
trans-diastereomers of 4-vinylsyringol dimer
cis-4,6-dimethoxy-5-hydroxy-1-methyl-3-(3′,5′-dimethoxy-4′-hydroxyphenyl)indane and
trans-4,6-dimethoxy-5-hydroxy-1-methyl-3-(3′,5′-dimethoxy-4′-hydroxyphenyl)indane and the vinylsyringol trimer in trace amounts. The phenylindane were isolated by preparative HPLC and was clearly identified by nuclear magnetic resonance spectroscopy. Besides sinapic acid and its decarboxylated derivative, 4-vinylsyringol, this newly identified 4-vinylsyringol dimer was present in the deodistillate of processed rapeseed oil in significant amounts (sinapic acid, approx. 500
mg/kg, 4-vinylsyringol, approx. 200
mg/kg and 4-vinylsyringol dimer, approx. 3.50
g/kg). Additionally, the phenylindane was also detected in small amounts (6.4–63.0
mg/kg or trace amounts, respectively) in commercial rapeseed oils. The newly identified phenylindane compound had a high antioxidative potential (3.9 trolox-eq.) and might be an important phenolic compound in commercial deodistillate and rapeseed oils.
4-Vinylsyringol was produced by decarboxylation from sinapic acid. To evaluate the antioxidant activity of 4-vinylsyringol, 500 ppm of 4-vinylsyringol, sinapic acid, or α-tocopherol was added to ...soybean oil and the oxidation processes were monitored by the peroxide value (PV), the thiobarbituric acid reactive substances value (TBARS) assay, and
1
H-NMR spectroscopy. The results obtained by PV and TBARS indicated that soybean oil containing 4-vinylsyringol (SBO-VS) showed the highest oxidative stability.
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H-NMR analysis also showed concurring results. After 19 days of oxidation, the degradation rates of linoleic acid (4.2 %) and linolenic acid (4.4 %) in SBO-VS were significantly lower than those in other oils. Secondary oxidation products (i.e. aldehydes) were undetectable in SBO-VS by
1
H NMR, whereas concentrations of such compounds in soybean oils containing α-tocopherol or sinapic acid were 38.0 ± 0.4 and 2.75 ± 0.2 mM oil, respectively. In addition, synergistic antioxidant effect between any two antioxidants was not observed.
For a long time, beer staling has been a prime concern in brewery research. Yet, to improve flavor stability, better knowledge of all chemicals involved is still needed. From our aroma extract ...dilu-tion analyses (AEDA) applied to naturally aged lager beers emerged an old-beer-like odorant at RICP - SIL 5 CB = 1532 and RIFFAP = 2809, with a FD value close to that of trans-2-nonenal (the well-known cardboard off-flavor found in aged beers). Specific phenol extraction, GC cold trapping, and mass spectrometry (electron impact and chemical ionization) enabled us to identify it as 4-vinylsyringol. Although already mentioned in some fresh beers, this compound had never been highlighted as involved in the aging process of lager beers. Keywords: Beer; storage; aging; stale; flavor; GC olfactometry; 4-vinylsyringol
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