A comparison of the antioxidant properties of steryl ferulates with tocopherol at high temperatures

Different effects of tocopherol natural extract on sunflower oil stability under frying and accelerated storage conditions: A comprehensive study on the fate of major and minor components of oil, and added tocopherols

The effect of adding a tocopherol-rich natural extract (TNE) at 0.1 % and 0.5 % on sunflower oil stability under frying and accelerated storage conditions was studied using 1H NMR and DI-SPME-GC/MS. The impact was more pronounced at the higher enrichment level under both conditions. During frying conditions, oil stability significantly decreased due to accelerated degradation of linoleate and minor components (tocopherols, squalene and sterols), along with a marked increase in oil viscosity. Additionally, the selective generation of aldehydes occurred, with the formation of alkanals, E-2-alkenals and toxic oxygenated α,β-unsaturated aldehydes being lagged. Under storage, TNE initially promoted linoleate degradation and the formation of monohydroperoxy-octadecadienoates but delayed their transformation into secondary or further compounds. Similarly, the degradation of oil minor components occurred more slowly. Tocopherol-derived metabolites varied depending on processing conditions. Pristane was the most abundant during frying, while 4,8,12,16-tetramethylheptadecan-4-olide predominated under storage conditions. Formyl derivatives were identified for the first time.

The Effect of High-Temperature Heating on Amounts of Bioactive Compounds and Antiradical Properties of Refined Rapeseed Oil Blended with Rapeseed, Coriander and Apricot Cold-Pressed Oils

Cold-pressed oils are rich sources of bioactive substances, which may protect triacylglycerols from degradation during frying. Nevertheless, these substances may decompose under high temperature. This work considers the content of bioactive substances in blends and their changes during high-temperature heating. Blends of refined rapeseed oil with 5% or 25% in one of three cold-pressed oils (rapeseed, coriander and apricot) were heated at 170 or 200 °C in a thin layer on a pan. All non-heated blends and cold-pressed oils were tested for fatty acid profile, content and composition of phytosterols, tocochromanols, chlorophyll and radical scavenging activity (RSA) analyzed by 2,2-diphenyl-1-picrylhydrazyl (DPPH), and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) assays. Moreover, the stability of phytosterols, tocochromanols, DPPH and ABTS values was determined in heated blends. All tocochromanols were lost during the heating process, in particular, at 200 °C. However, there were some differences between homologues. α-Tocopherol and δ-tocopherol were the most thermolabile and the most stable, respectively. Phytosterols were characterized by very high stability at both temperatures. We observed relationships between ABTS and DPPH values and contents of total tocochromanols and α-tocopherol. The obtained results may be useful in designing a new type of fried food with improved health properties and it may be the basis for further research on this topic.

An Insight into the Thermal Degradation Pathway of γ-Oryzanol and the Effect on the Oxidative Stability of Oil

Thermal stability and antioxidant ability of γ-oryzanol in oil have been widely studied. However, further research is needed to explore its thermal degradation products and degradation pathways. The thermal degradation products of γ-oryzanol in stripped soybean oil were identified and quantified by employing high-performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS) during heating at 180 °C. The results revealed that γ-oryzanol undergoes ester bond cleavage to form trans-ferulic acid and free sterols, and trans-ferulic acid generated intermediate compound 4-vinylguaiacol, which ultimately generated vanillin. Analysis of kinetic and thermodynamic parameters revealed the thermal stability ranking of the four components of γ-oryzanol as follows: CampFA > CAFA > 24MCAFA > SitoFA. Furthermore, γ-oryzanol exhibited superior antioxidant activity at lower temperatures. The results of this study provide a theoretical basis for a better understanding of the thermal stability and antioxidant properties of γ-oryzanol in oil under thermal oxidation conditions.

Phenolipids as new food additives: from synthesis to cell-based biological activities

Increasing interest has been shown in phenolic compounds for enhancing food quality, but their hydrophilicity restricts application in lipophilic systems. Therefore, in this study, twelve hydroxycinnamates derivatives (alkyl and steryl esters of sinapic acid (SA), caffeic acid (CA), and ferulic acid [FA]) were synthesised and evaluated for antioxidant and cytotoxic characteristics. CA esters had the highest radical scavenging activity (RSA) analysed by 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) assays. Values of inhibitory concentration (IC₅₀) of synthesised compounds were related to their structure and lipophilicity. The effect of these hydroxycinnamic acid esters on the antioxidant potential of real samples (rapeseed oil, margarine and mayonnaise) was estimated. None of the investigated derivatives significantly affected the viability of the model intestinal cells Caco2, while the octyl esters demonstrated a toxic effect at low concentrations. The synthesised esters exerted cytotoxic and anti-proliferative effects against transformed cell lines (HeLa and A549). Octyl esters were potent anticancer compounds on two human cancer cell lines. The synthesised phenolipids, as valuable and safe antioxidant additives, can find broader applications in the production of fat-based products to prevent oxidation processes, extend their shelf life and improve quality.

Steryl Sinapate as a New Antioxidant to Improve Rapeseed Oil Quality during Accelerated Shelf Life

In recent years, steryl esters have become an attractive for the cosmetic, pharmaceutical, and food industries. Hence, the effect of exogenous antioxidant, β-sitosteryl sinapate on oxidative stability and antioxidant activity (AA) of refined rapeseed oil was evaluated by the accelerated shelf-life test. Oxidative parameters of refined rapeseed oil—peroxide value (PV), anisidine value (p-AnV), acid value (AV), and spectrophotometric indices (K₂₃₂, K₂₆₈)—increased during storage. However, the addition of β-sitosteryl sinapate caused a decrease of the primary and secondary oxidation products in the supplemented oils in comparison with the control sample. Moreover, oils with steryl ester had higher AA than oil without the synthetic antioxidant. The accelerated storage negatively affected the antioxidant potential of refined and enriched oils causing the AA decrease by 25–54% and 7–15%, respectively. Studies have consistently demonstrated beneficial associations between the presence of β-sitosteryl sinapate in oil samples and the inhibition of their oxidative degradation under the accelerated conditions. Additionally, the possibility of using the synchronous fluorescence (SF) spectroscopy and excitation–emission matrix (EEM) fluorescence spectroscopy for identification and observing changes in main fluorescent components present in non-supplemented and supplemented rapeseed oils during the accelerated storage was attempted.

A Simple and Efficient Method for Synthesis and Extraction of Ethyl Ferulate from γ-Oryzanol

Ethyl ferulate (EF) is a ferulic acid (FA) derivative with high commercial value. It is not found naturally and is mostly synthesized from FA via esterification with ethanol. The present work aimed to synthesize the EF from γ-oryzanol, a natural antioxidant from rice bran oil via acid-catalyzed transethylation at refluxing temperature of ethanol. The reaction was optimized by central composite design (CCD) under response surface methodology. Based on the CCD, the optimum condition for the synthesis of EF from 0.50 g of γ-oryzanol was as follows: γ-oryzanol to ethanol ratio of 0.50:2 (g/mL), 12.30% (v/v) H₂SO₄, and a reaction time of 9.37 h; these conditions correspond to a maximum EF yield of 87.11%. Moreover, the optimized transethylation condition was further validated using 12.50 g of γ-oryzanol. At the end of the reaction time, distilled water was added as antisolvent to selectively crystallize the co-products, phytosterol and unreacted γ-oryzanol, by adjusting the ethanol concentration to 49.95% (v/v). The recovery yield of 83.60% with a purity of 98% of EF was achieved. In addition, the DPPH and ABTS assays showed similar antioxidant activities between the prepared and commercial EF.

Antioxidant interaction of α-tocopherol, γ-oryzanol and phytosterol in rice bran oil

In this study, purified rice bran oil (RBO) was used as a lipid matrix model to study the individual and binary antioxidant capacity of the minor constituents (α-tocopherol, γ-oryzanol and phytosterol) added at different concentrations and ratios. The results revealed that concentration influenced on the oxidation stability and scavenging capacity, while ratio mainly affected the type of interaction or the degree of synergism or antagonism. It was important to notice that the antioxidant capacity of α-tocopherol would decrease under high concentration. Besides, the inhibition of phytosterol on α-tocopherol and the formation of hydrogen bond between γ-oryzanol and phytosterol were speculated by the interactions of these minor constituents. This work helps to select efficient combinations for stabilizing the anti-oxidation of nutrient enriched RBO or provide suggestions for moderate retain of minor constituents in RBO.

Synthesis of Steryl Hydroxycinnamates to Enhance Antioxidant Activity of Rapeseed Oil and Emulsions

In recent years, steryl esters have found potential applications in food, pharmaceutical and cosmetic industries. Therefore, three hydroxycinnamate steryl esters (HSEs): β-sitosteryl sinapate (β-SSA), β-sitosteryl caffeate (β-SCA), and β-sitosteryl ferulate (β-SFA) were synthesized by chemical approach and their antioxidant activity (AA) were analyzed by 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) assays. The values of inhibitory concentration (IC₅₀) of each ester needed to inhibit 50% of the DPPH radical (IC_50(DPPH) = 238.9, 78.3, 290.0 µmol/L for β-SSA, β-SCA, and β-SFA, respectively) and ABTS radical cation (IC_50(ABTS) = 174.6, 106.7, 206.0 µmol/L for β-SSA, β-SCA, and β-SFA, respectively) were estimated and compared with antioxidant potential of phenolic acids. Moreover, the effect of HSEs addition in the concentrations range between 0.01% and 0.5% on the AA of refined rapeseed oil, mayonnaise and margarine was evaluated. Chemical structures of the synthesized HSEs and their concentrations strongly affect the AA of fat products. Oil and emulsions supplemented with higher concentrations of HSEs had significantly higher AA than control samples. Unfortunately, lower concentrations of HSEs (0.01% and 0.02%) did not increase the AA of fat products. However, steryl phenolates added in higher amounts can be considered as potential antioxidants delaying the oxidation processes of studied fats.

Microwave (MW) promoted high yield expedient synthesis of steryl ferulates--A class of novel biologically active compounds: A comparative study of their antioxidant activity with that of naturally occurring γ-oryzanol

Synthetic steryl ferulates [3-O-(trans-4-feruloyl)-sterols] are currently gaining considerable importance in recent years to be used as nutraceuticals and food additives as well as in pharmaceutical applications substituting γ-oryzanol - a class of naturally occurring steryl ferulates having potent antioxidant and other organoleptic properties. Considering the importance of this class of compounds coupled with green technology associated with microwave energy (MW) in organic synthesis, we report here an expedited and high yield synthesis of steryl ferulates from abundant steroids, viz., cholesterol, cholestanol, stigmasterol, stigmastanol, β-sitosterol, β-campesterol, β-campestanol and ergosterol applying MW energy in the crucial step of esterification process of sterols with trans-4-O-acetylferulic acid to furnish their esterified products, viz., 3-O-(trans-4-O-acetylferuloyl)-sterols for their eventual deprotection to their respective steryl ferulates. We further report an efficient and scalable process of producing acetylferulic acid. Testing of synthesized steryl ferulates against antioxidant assays has also been highlighted.

Effect of different germination conditions on antioxidative properties and bioactive compounds of germinated brown rice

This study investigates antioxidative activity and bioactive compounds of ungerminated brown rice (UBR) and germinated brown rice (GBR). We used two rice cultivars (Oryza sativa L.), Taiwan Japonica 9 (TJ-9) and Taichung Indica 10 (TCI-10), as the materials in our experiments. The conditions for inducing germination are soaking time in water 24, 48, or 72 h; temperature 26 or 36°C; incubation in light or darkness; and open or closed vessels, in which the antioxidative activities and bioactive compounds of GBR were determined. We found that, in order to maximize antioxidative activity and bioactive compounds, germination should be under higher temperature (36°C), long soaking time (72 h), darkness, and closed vessel. GBR contains much higher levels of antioxidative activity and bioactive compounds than ungerminated brown rice (UBR). We found a strong correlation between antioxidative activities (DPPH radical scavenging ability, reducing power, and Trolox equivalent antioxidant capacity) and bioactive compounds (γ-oryzanols, tocopherol, and tocotrienol). Higher temperature (36°C) is also conducive to the production of GABA in GBR. These results are considered very useful research references for the development of future functional foods and additives.

Edible coatings as encapsulating matrices for bioactive compounds: a review

Edible coatings can extend the shelf-life of many foods, controlling moisture and solute migration, gas exchange and oxidative reaction rates. Besides, edible coatings can be used as carriers of bioactive compounds to improve the quality of food products such as antioxidants, antimicrobials, flavors and probiotics. These approaches can be useful to extend shelf-life as well as provide a functional product. When edible coatings are used as a matrix holding bioactive compounds remarkable benefits arise; off odors and flavors can be masked, bioactive compounds are protected from the environment, and controlled release is allowed. In this sense, the present review will be focused on analyzing the potential use of encapsulation with edible coatings to incorporate bioactive compounds, solving the disadvantages of direct application.

Fat-soluble nutraceuticals and their composition in heat-processed wheat germ and wheat bran

Nutraceuticals availability in heat-processed foods is considered to be the index for healthy food. This study has made an attempt to optimize the temperature to retain nutraceuticals in wheat bran (WB) and wheat germ (WG). Heated WG (130 °C & 140 °C) and WB (140 °C & 150 °C) were analyzed for sensory profiles. Extracted oils were subjected to physicochemical parameter as well as its nutraceuticals. Increased oil yield, color values and reduced free fatty acids were found with varied temperatures. Fat-soluble compounds total tocols, steryl ferulates and carotenoids found in WG (0.316, 0.058 and 0.011%) and WB (0.228, 0.595 and 0.015%) and maximum reductions started in WG (0.183%, 0.034% and 0.004%) at 130 °C. The free radical-scavenging activities of control samples showed high EC50 values than processed samples; however, no differences were observed between two temperatures. Study may clearly spell out that the reduced nutraceuticals observed after subjecting food raw materials to optimum temperature eventually lead to its quality.

The effect of in vitro digestion on steryl ferulates from rice (Oryza sativa L.) and other grains

Polished and cargo rice, wild rice, rice bran, corn bran, and wheat bran were subjected to a static in vitro digestion model, to monitor changes in their steryl ferulate content and composition. Free sterols, possible hydrolysis products of steryl ferulates, were also measured. Additionally, steryl ferulate bioaccessibility was calculated as the percentage of steryl ferulates liberated from the grain matrix into the digestive juice. Steryl ferulate content ranged between 6.1 and 3900 μg/g and decreased by 1-63% due to digestion. A parallel increase in free sterols of more than 70% was observed in all samples. Additionally, bioaccessibility of steryl ferulates was found to be almost negligible. These findings suggest that intestinal enzymes immediately hydrolyze steryl ferulates, which are liberated from the grain matrix, and thus they are practically unavailable for absorption in the small intestine. This further indicates that the hydrolysis products of steryl ferulates could be bioactive in the gut.

Characterization of high-value bioactives in some selected varieties of Pakistani Rice (Oryza sativa L.)

The present study reports the composition and variation of fatty acids, sterols, tocopherols and γ-oryzanol among selected varieties namely Basmati Super, Basmati 515, Basmati 198, Basmati 385, Basmati 2000, Basmati 370, Basmati Pak, KSK-139, KS-282 and Irri-6 of Pakistani rice (Oryza sativa L). Oil content extracted with n-hexane from different varieties of brown rice seed (unpolished rice) ranged from 1.92% to 2.72%. Total fatty acid contents among rice varieties tested varied between 18240 and 25840 mg/kg brown rice seed. The rice tested mainly contained oleic (6841-10952 mg/kg) linoleic (5453-7874 mg/kg) and palmitic acid (3613-5489 mg/kg). The amounts of total phytosterols (GC and GC-MS analysis), with main contribution from β-sitosterol (445-656 mg/kg), campesterol (116-242 mg/kg), Δ(5)-avenasterol (89-178 mg/kg) and stigmasterol (75-180 mg/kg) were established to be 739.4 to 1330.4 mg/kg rice seed. The content of α-, γ- and δ-tocopherols as analyzed by HPLC varied from 39.0-76.1, 21.6-28.1 and 6.5-16.5 mg/kg rice seed, respectively. The amounts of different γ-oryzanol components (HPLC data), identified as cycloartenyl ferulate, 24-methylene cycloartanyl ferulate, campesteryl ferulate and β-sitosteryl ferulate, were in the range of 65.5-103.6, 140.2-183.1, 29.8-45.5 and 8.6-10.4 mg/kg rice seed, respectively. Overall, the concentration of these bioactives was higher in the Basmati rice cultivars showing their functional food superiority. In conclusion, the tested varieties of Pakistani rice, especially the Basmati cultivars, can provide best ingredients for functional foods.

Minor components in food oils: a critical review of their roles on lipid oxidation chemistry in bulk oils and emulsions

Food oils are primarily composed of triacylglycerols (TAG), but they may also contain a variety of other minor constituents that influence their physical and chemical properties, including diacylglycerols (DAG), monoacylglycerols (MAG), free fatty acids (FFA), phospholipids (PLs), water, and minerals. This article reviews recent research on the impact of these minor components on lipid oxidation in bulk oils and oil-in-water emulsions. In particular, it highlights the origin of these minor components, the influence of oil refining on the type and concentration of minor components present, and potential physicochemical mechanisms by which these minor components impact lipid oxidation in bulk oils and emulsions. This knowledge is crucial for designing food, pharmaceutical, personal care, and other products with improved stability to lipid oxidation.

Effects of genotype and environment on steryl ferulates in wheat and rye in the HEALTHGRAIN diversity screen

The effects of genetic and environmental factors on the content and composition of steryl ferulates in wheat and rye were studied. The wheat and rye genotypes were grown at the same location in Hungary over three consecutive years (28 genotypes) or at four different locations across Europe during a single year (12 genotypes). The steryl ferulates were analyzed using HPLC. The genotype and growing location significantly affected the content and composition of wheat steryl ferulates, whereas the year of growth did not result in considerable variation. Less variation was observed in rye, due to fewer genotypes. Campestanyl and sitostanyl ferulates were the main species in both cereals. Knowledge of the natural variation in steryl ferulates and other bioactive compounds allows cultivators and plant breeders to select genotypes with high, stable levels of beneficial compounds. Thus, it is possible to enhance the intake of health-promoting compounds from natural sources.