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The impact of rice bran stabilization thermal treatments on oxidative stability, extractability, and antioxidant potential was investigated. Freshly milled rice bran samples of the variety “Ld 368 –red” were subjected to four heat treatments: steaming, hot air drying, microwave treatment, and a combination of microwave and steaming. Solvent extraction was used to obtain rice bran oil (RBO). The Phenolic, γ-oryzanol contents and antioxidant potential of RBO were analyzed. Oil yield, free fatty acid content (FFA), and peroxide value (PV) were measured during 50-days storage at room temperature, with data collected at an interval of 10 days. The highest extraction yield was in coupled treatment (22.26 %). The coupled treatment and microwave were the most effective for the stabilization of rice bran in terms of oxidative stability, which provided the lowest FFA value (2.950 % & 2.993 %) and PV (0.518 & 0.620 mEqv/kg oil) (p ≤ 0.05). The lowest increment of FFA (2.945 %) and PV (4.23 mEqv/kg) was detected in RB stabilized by coupled treatment in 50 days of storage time. The microwaved sample exhibited the highest total phenolic content (4.147±0.190 mg GAE/g of extract), γ-oryzanol content (1.536±0.0173 %), and the highest antioxidant activity/ lowest IC50 value among the stabilized sample.
Rice bran is a nutrient-rich and resource-dense byproduct of rice milling. The primary cause of rice bran utilization limitation is oxidative deterioration and inadequate storage facilities. Improving stability to extend the shelf-life of rice bran has thus become an utmost necessity. This study aimed to stabilize raw fresh rice bran (RB) by using dry heat methods at 120 °C (233, 143, and 88 min) and 130 °C (86, 66, and 50 min). The results indicated that after dry heat pretreatment, peroxidase levels were at 90%, and the storage stability of dry-heat-stabilized RB was better. However, with an increase in treatment temperature and time, the peroxidase activity improved while the lipase activity decreased to a certain extent without significant changes. The total saturated and unsaturated fatty acids were significantly unchanged during storage, while oleic/linoleic acid increased substantially by 1% at 120 °C for 88 min. The increase in treatment time and temperature was beneficial in controlling the fatty acid values. However, extended treatment time caused an increase in the peroxide value and MDA. The essential and non-essential amino acid ratios, which evaluate a protein’s nutritional value, remained relatively stable. The essential subunit of rice bran protein was not affected by the temperature and time of dry heat treatment and storage time.
Scope:
The purpose of the study is to characterize the chemical diversity in Rice bran (RB) lipidome and determine whether daily RB consumption for 4 weeks may modulate plasma lipid profiles in children.
Methods and results:
Untargeted and targeted lipidomics via ultra-performance liquid chromatography coupled with high-resolution tandem mass spectrometry (UPLC-MS/MS) were applied to identify bioactive RB lipids from a collection of 17 rice varieties. To determine the impact of RB (Calrose-USA variety) supplementation on plasma lipid profile, a secondary analysis of plasma lipidome was conducted on data recorded in a clinical study (NCT01911390, n = 18 moderately hypercholesterolemic children) before and after 4 weeks of dietary intervention (15 g/d) with a control or RB supplemented snack. Untargeted lipidomic revealed 118 lipids as the core of lipidome across all 17 varieties among which phospholipids were abundant and oxylipins present. Phytoprostanes and phytofurans were quantified and characterized. Lipidome analysis of the children plasma following RB consumption revealed the presence of novel polar lipids and oxylipins alongside putative modulations in endocannabinoids associated with RB consumption.
Conclusion:
The investigation of novel polar lipids, oxylipins, phytoprostanes, and phytofurans in RB extracts provides support for new health-promoting properties especially interesting for people at risk for cardiometabolic disease. This article is protected by copyright. All rights reserved.
During the oxidation of lipids in food or in vivo, fatty acids are initially converted to hydroperoxides, which undergo decomposition to various secondary decomposition products, including aldehydes and alkyl-furans. Aldehydes and alkyl-furans reduce the sensory quality of food by contributing to rancidity, and aldehydes reduce nutritional value by reacting with some essential nutrients such as lysine and thiamine. In vivo, reactions of aldehyde with proteins and DNA contribute to the pathogenesis of physiological disorders. Conversion of fatty acid hydroperoxides to aldehydes is generally believed to involve free radical reactions. However, it was recently hypothesized that lysine can catalyze the non-radical conversion of hydroperoxides to aldehydes. Thus the aim of the present study was to determine such lysine-catalysed conversion of linoleic acid hydroperoxides to aldehydic products. Linoleic acid hydroperoxides were prepared by the photosensitized oxidation of linoleic acid. The mixture of hydroperoxides was reacted with lysine, in the presence of a radical scavenger, and the organic fraction analysed by gas chromatography-mass spectrometry (GC-MS). Hexanal was detected as a major aldehydic product. The alkylfuran, 2-pentylfuran was also surprisingly detected under these conditions, and a pathway for its lysine-catalysed formation via the highly cytotoxic aldehyde, 4-hydroxy-2-nonenal proposed. The results of this study imply that, in the prevention of lipid oxidation-associated food deterioration and development of physiological disorders, more attention should be paid to pathways not involving free radical reactions, and which cannot be prevented by radical scavenging antioxidants.
Rice is one of the most important crops throughout the world, as it contributes toward satisfying the food demand of much of the global population. It is well known that rice production generates a considerable number of by-products, among which rice bran deserves particular attention. This by-product is exceptionally rich in nutrients, since it contains a wide spectrum of macronutrients (proteins, fats, carbohydrates) as well as dietary fibers and bioactive compounds. However, rice bran is usually wasted or just used for the production of low-cost products. The lipidic fraction of rice bran contains an unsaponifiable fraction that is rich in such functional components as tocopherols, γ-oryzanol, tocotrienols, and phytosterols. This lipidic fraction can be extracted to obtain rice bran oil (RBO), a high value-added product with unique health properties as a result of its high concentration in γ-oryzanol, a powerful antioxidant mixture of bioactive molecules. Conventional extraction methods employ hexane as the solvent, but these methods suffer from some drawbacks linked to the toxicity of hexane for humans and the environment. The aim of the review presented herein is to point out the new green technologies currently applied for the extraction of RBO, by highlighting reliable alternatives to conventional solvent extraction methods that are in line with the twelve principles of green chemistry and a circular economy.
Rice bran is an invaluable by-product of paddy processing industry. It is rich in minerals, protein, lipids, and crude fiber. In addition, it also possesses compounds with anti-oxidant, anti-allergic, anti-diabetic, and anti-cancer properties. It forms a basis for the extraction of rice bran oil and preparation of various functional foods with health benefits and potential to prevent chronic health issues. Nevertheless, the rapid deterioration of bran upon storage acts as a major limitation in exploiting the full potential of rice bran. In this review, we have discussed three strategies to address rapid rancidity of rice bran and enhance its shelf life and storability vis-a-vis emphasizing the importance of rice bran in terms of its nutritional composition. One strategy is through exploitation of the null mutations in the genes governing lipases and lipoxygenases leading to nonfunctional enzymes (enzyme deficient approach), another strategy is through reducing the PUFA content that is more prone to oxidation (substrate deficient approach) and a third strategy is through enhancing the antioxidant content that effectively terminate the lipid peroxidation by donating the hydrogen atom.
Oxylipins are bioactive mediators that play diverse roles in (patho)physiology. We developed a sensitive and selective ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method for the simultaneous profiling of 57 targeted oxylipins derived from five major n-6 and n-3 polyunsaturated fatty acids (PUFAs) that serve as oxylipin precursors, including linoleic (LA), arachidonic (AA), alpha-linolenic (ALA), eicosapentaenoic (EPA), and docosahexaenoic (DHA) acids. The targeted oxylipin panel provides broad coverage of lipid mediators and pathway markers generated from cyclooxygenases, lipoxygenases, cytochrome P450 epoxygenases/hydroxylases, and non-enzymatic oxidation pathways. The method is based on combination of protein precipitation and solid-phase extraction (SPE) for sample preparation, followed by UPLC-MS/MS. This is the first methodology to incorporate four hydroxy-epoxy-octadecenoic acids and four keto-epoxy-octadecenoic acids into an oxylipin profiling network. The novel method achieves excellent resolution and allows in-depth analysis of isomeric and isobaric species of oxylipin extracts in biological samples. The method was quantitatively characterized in human plasma with good linearity (R = 0.990-0.999), acceptable reproducibility (relative standard deviation (RSD) < 20% for the majority of analytes), accuracy (67.8 to 129.3%) for all analytes, and recovery (66.8-121.2%) for all analytes except 5,6-EET. Ion enhancement effects for 28% of the analytes in tested concentrations were observed in plasma, but were reproducible with RSD < 17.2%. Basal levels of targeted oxylipins determined in plasma and serum are in agreement with those previously reported in literature. The method has been successfully applied in clinical and preclinical studies.
Rice bran oil (RBO) is gaining popularity among other traditionally used cooking oils because of its better cooking quality, prolonged shelf life and well-balanced fatty acid composition as well as the presence of many antioxidant components. RBO has lower viscosity and relatively high smoke point, which make it as healthy cooking oil. RBO is rich in vitamin E (both tocopherols and tocotrienols) and bioactive phytonutrients, which include phytosterols, γ-oryzanol, squalene and triterpene alcohols. All of these compounds exhibit high antioxidant, anti-inflammatory, hypocholesterolaemic, antidiabetic and anticancer activities. The dietary intake of RBO has been reported to lower the levels of blood cholesterol, blood pressure and blood glucose and can help to reduce inflammation and symptoms of metabolic syndrome. RBO helps to boost the immune system and prevent the process of premature ageing and age-related neurodegenerative diseases. Because of its cardiac-friendly phytochemicals and antioxidant potentials, RBO has been categorized as healthy edible oil for human consumption and has attained the status of “heart-healthy oil”. As per scientific evidences, it is suggested that a daily intake of 50 g of RBO besides dietary and lifestyle modifications may be considered enough to attain its beneficial effects in reducing the risk of chronic diseases, in particular the cardiovascular diseases. This chapter discusses the nutritional and phytochemical components of RBO, their mechanism of action as well as health benefits in the prevention and management of chronic diseases.
Oxylipins formed from polyunsaturated fatty acids (PUFAs) are the main mediators of PUFA effects in the body. They are formed via cyclooxygenase, lipoxygenase, and cytochrome P450 pathways, resulting in the formation of prostaglandins, thromboxanes, mono-, di-, and tri-hydroxy fatty acids (FAs), epoxy FAs, lipoxins, eoxins, hepoxilins, resolvins, protectins (also called neuroprotectins in the brain), and maresins. In addition to the well-known eicosanoids derived from arachidonic acid, recent developments in lipidomic methodologies have raised awareness of and interest in the large number of oxylipins formed from other PUFAs, including those from the essential FAs and the longer-chain n-3 (ω-3) PUFAs. Oxylipins have essential roles in normal physiology and function, but can also have detrimental effects. Compared with the oxylipins derived from n-3 PUFAs, oxylipins from n-6 PUFAs generally have greater activity and more inflammatory, vasoconstrictory, and proliferative effects, although there are notable exceptions. Because PUFA composition does not necessarily reflect oxylipin composition, comprehensive analysis of the oxylipin profile is necessary to understand the overall physiologic effects of PUFAs mediated through their oxylipins. These analyses should include oxylipins derived from linoleic and α-linolenic acids, because these largely unexplored bioactive oxylipins constitute more than one-half of oxylipins present in tissues. Because collated information on oxylipins formed from different PUFAs is currently unavailable, this review provides a detailed compilation of the main oxylipins formed from PUFAs and describes their functions. Much remains to be elucidated in this emerging field, including the discovery of more oxylipins, and the understanding of the differing biological potencies, kinetics, and isomer-specific activities of these novel PUFA metabolites.
Oxylipins, including eicosanoids, affect a broad range of biological processes, such as the initiation and resolution of inflammation. These compounds, also referred to as lipid mediators, are (non-) enzymatically generated by oxidation of polyunsaturated fatty acids such as arachidonic acid (AA). A plethora of lipid mediators exist which makes the development of generic analytical methods challenging. Here we developed a robust and sensitive targeted analysis platform for oxylipins and applied it in a biological setting, using high performance liquid chromatography coupled to tandem mass spectrometry (HPLC-MS/MS) operated in dynamic multiple reaction monitoring (dMRM). Besides the well-described AA metabolites, oxylipins derived from linoleic acid, dihomo-γ-linolenic acid, α-linolenic acid, eicosapentaenoic acid and docosahexaenoic acid were included. Our comprehensive platform allows the quantitative evaluation of approximately 100 oxylipins down to low nanomolar levels. Applicability of the analytical platform was demonstrated by analyzing plasma samples of patients undergoing cardiac surgery. Altered levels of some of the oxylipins, especially in certain monohydroxy fatty acids such as 12-HETE and 12-HEPE, were observed in samples collected before and 24 h after cardiac surgery. These findings indicate that this generic oxylipin profiling platform can be applied broadly to study these highly bioactive compounds in relation to human disease.
Figure
LC-MS/MS chromatogram of 104 oxylipins on a Triple Quadrupole MS system employing dynamic MRM in the Negative Ion Electrospray mode
Electronic supplementary material
The online version of this article (doi:10.1007/s00216-012-6226-x) contains supplementary material, which is available to authorized users.
Oxidative stress is a core abnormality responsible for disease progression in nonalcoholic fatty liver disease (NAFLD). However, the pathways that contribute to oxidative damage in vivo are poorly understood. Our aims were to define the circulating profile of lipid oxidation products in NAFLD patients, the source of these products, and assess whether their circulating levels reflect histological changes in the liver. The levels of multiple structurally specific oxidized fatty acids, including individual hydroxy-eicosatetraenoic acids (HETE), hydroxy-octadecadenoic acids (HODE), and oxo-octadecadenoic acids (oxoODE), were measured by mass spectrometry in plasma at time of liver biopsy in an initial cohort of 73 and a validation cohort of 49 consecutive patients. Of the markers monitored, 9- and 13-HODEs and 9- and 13-oxoODEs, products of free radical-mediated oxidation of linoleic acid (LA), were significantly elevated in patients with nonalcoholic steatohepatitis (NASH), compared with patients with steatosis. A strong correlation was revealed between these oxidation products and liver histopathology (inflammation, fibrosis, and steatosis). Further analyses of HODEs showed equivalent R and S chiral distribution. A risk score for NASH (oxNASH) was developed in the initial clinical cohort and shown to have high diagnostic accuracy for NASH versus steatosis in the independent validation cohort. Subjects with elevated oxNASH levels (top tertile) were 9.7-fold (P < 0.0001) more likely to have NASH than those with low levels (bottom tertile). Collectively, these findings support a key role for free radical-mediated linoleic acid oxidation in human NASH and define a risk score, oxNASH, for noninvasive detection of the presence of NASH.
The fatty acid composition of rapeseed seeds plays an important role in oil quality for human nutrition and a healthy diet. A deeper understanding of fatty acid composition and lipid profiles in response to different nitrogen managements is critical for producing healthier rapeseed oil for the human diet. The fatty acid composition and lipid profiles were characterized through targeted GC-MS and lipidomics analysis (UPLC-MS) in this study. The results showed that nitrogen management significantly altered the fatty acid composition, thereby influencing oil quality when it is used to maximize the seed yield of rapeseed. Several fatty acid components (particularly oleic acid, linoleic acid, and linolenic acid) decreased significantly with increasing N application rate. A total of 1212 differential lipids in response to different N levels in the two varieties were clearly identified, that can be categorized into five classes, including 815 glycerolipids (GLs), 195 glycerophospholipids (GPs), 155 sphingolipids (SPs), 32 sterols (STs), and 15 fatty acyls (FAs). These differential lipids are likely to participate in lipid metabolism and signal transduction. Co-expression lipid modules were determined, and the key lipids, such as triglyceride (20:0/16:0/16:0; 18:0/18:1/18:3; 8:0/11:3/18:1), were found to be strongly related to several predominant fatty acids such as oleic acid and linoleic acid. The results further imply that some identified lipids are involved with lipid metabolism and could affect the fatty acid composition, which provide a theoretical guidance for increasing seed oil in Brassica napus.
Rice bran is rich in nutrients and bioactive components, which plays an important role in reducing dyslipidemia and regulating intestinal flora. However, due to the rice bran’s instability resulting from rancidity during storage, the development is limited. E-nose, GC-MS and E-tongue were used to monitor the flavor and bitterness of different stabilized rice bran during accelerated storage, and the change of physicochemical properties in rice bran was determined. The rice bran flavor significantly changed after five stabilization treatments. The bitterness increased during storage, but the growth was small (from 7.39 to 7.62). Besides, after stabilization treatments, lipase (LA) activities gradually decreased from 10.11 to 2.03 mg/g, and lipoxygenase (Lox) activities decreased from 3.71 to 1.38 U/g. These results comprehensively elucidate changes in volatile composition, bitterness and physicochemical properties of stabilized rice bran samples during storage and lay the foundation for improving its acceptability and edibility in the future.
Enzymatic and nonenzymatic oxidation of linoleic (LA) and α-linolenic acid (ALA) during pressing and storage of plant oils leads to a variety of oxylipins. We pressed oils from flaxseeds, rapeseeds, and sunflower seeds and analyzed the oxylipin pattern in freshly pressed oils. 9-/13-Hydro(pero)xy-LA/-ALA occurred in high concentration resulting probably from lipoxygenase-catalyzed reactions as well as autoxidation and photooxidation. However, in flaxseed and rapeseed oil, the highest concentrations were found for the terminal epoxy-ALA (15(16)-EpODE) and the hardly known 15-hydroxy-LA (15-HODE, 80 mg/100 g in flaxseed oil). Oils were stored for 6 months and the peroxide value (PV) as well as oxylipin and secondary volatile aldehyde concentrations were determined. While lipid peroxidation in flaxseed oil was surprisingly low, the oxylipin concentration and PV massively increased in rapeseed oil dependent on oxygen availability. Oxylipin concentrations correlated well with the PV, while secondary volatile aldehydes did not reflect the changes of oxylipins and PVs. The comprehensive analysis of hydroxy-, epoxy-, and dihydroxy-LA/-ALA reveals new and unique insights into the composition of plant oils and ongoing oxidation processes.
Rapeseed oil has a similar oleic acid/linoleic acid ratio to human milk fat (HMF). However, it can hardly be used for human milk fat substitute (HMFS) synthesis due to high erucic acid content. In this study, Candida cylindracea lipase (CCL) was found to strongly discriminate against erucic acid. Free fatty acids containing low erucic acid and high oleic acid and linoleic acid were prepared from rapeseed oil hydrolysis catalyzed by CCL. The erucic acid content was only 1.58% (initial 8.70%), when the degree of hydrolysis reached 79.58%. The free fatty acids were used as acyl-donors in the acidolysis catalyzed by Novozym 40086. Considering acyl incorporation and migration, the optimum conditions were 1:8 (tripalmitin to acyl-donors), 40 °C and 2 h. The erucic acid content dropped to 0.97% in the HMFS. According to the Q-TOF-MS analysis, the HMFS was rich in 1,3-dioleoyl-2-palmitoyl-glycerol (18.20%) and 1-oleoyl-2-palmitoyl-3-linoleoyl-glycerol (17.96%), which was similar to HMF.
Wheat bran has a short shelf life, which could be prolonged by reducing the activity of enzymes in lipid degradation. In this study, high-intensity ultrasound treatment (400 W, 80% amplitude, 15 min), with or without cooling, was investigated for reducing the activity of lipase and peroxidase of wheat bran. Lipid stability parameters (free fatty acid content, peroxide value, anisidine value) of bran with coarse and reduced particle size (median 50th percentile diameter 503 and 177 μm, respectively) were followed under ambient or refrigerated storage conditions. Ultrasonic treatment without accompanying cooling inactivated 63% of lipase and 90% of peroxidase, but also decreased the antioxidant activity of bran by 13%. Compared with the untreated bran, the ultrasound-treated bran was darker, redder, and yellower. When ambiently stored, the critical anisidine value (10) of the unprocessed bran was exceeded after only 2 months, whereas the ultrasound-treated bran had an acceptable anisidine value for almost 12 months. Cooling during ultrasonication limits the ability to inactivate enzymes, and the reduction in bran particle size promotes its oxidative deterioration. The application of high-intensity ultrasound without cooling is beneficial for prolonging the oxidative stability of wheat bran compared to refrigerated storage.
The bran fraction of rice grains is used for extracting nutritious edible oil known as rice bran oil (RBO). In spite of its nutritional quality, bran lipids have a lower shelf-life due to the hydrolytic and oxidative rancidity. During the rice grain milling, endogenous lipases come in contact with storage lipids or triacylglycerols (TAGs) in the ruptured bran layers. The fatty acid ester bonds in the TAGs are hydrolyzed by the lipases causing the release of free fatty acids (FFAs) and glycerol. Further oxidation of these FFAs, especially the linoleic acid (18:2) are further oxidized by the action of lipoxygenases (LOXs). This reaction produced conjugated hydroperoxides of 18:2, which decompose and form secondary oxidation products responsible for the strong undesirable stale off-flavors. The outcome is a deterioration of bran lipids and significant loss of TAGs during RBO refining process. Therefore, this review aims to provide a holistic view on the current understanding of the catalog of genes and the underlying molecular mechanisms involved in triggering bran lipid rancidity. Generated knowledge about the individual genes will be crucial for developing advanced genome editing strategies to regulate rice bran lipid quality and stability.
Rice bran is one of the most valuable nutritional byproducts of rice milling. It is known to have an unacceptable flavor to consumers, so the development of reliable analytical methods to determine its unpleasant volatile compounds should be developed. Comparative volatile profiling of rice bran at different times of accelerated storage was performed using solid-phase microextraction (SPME) coupled to GC/MS, and the impact of stabilizing methods on the odor of rice bran was evaluated using E-nose, GC/MS and gas chromatography-olfactometry (GC-O) analyses. Sixty-five volatile compounds were identified and classified into six groups. Among them, the relative concentration of aldehydes increased with storage time, and hexanal was the compound with the highest content. Similar behavior was exhibited by ketones and alcohols, which were connected with early oxidation of rice bran. The main characteristic odor compounds of rice bran were vanillin, 2-methoxy-4-vinylphenol and 5-amino-2-methoxyphenol regarding ferulic acid. Through PCA, the volatile compounds of six kinds of rice bran were distinguished. The GC-O experiment verified that the processed products changed from the original grassy, oily flavor to vanilla, cheese, and caramel flavors. These results comprehensively elucidate the flavor characteristics of rice bran and provide important theoretical support for the development of rice bran products.
Storage lipid mobilization by lipases and lipoxygenases (LOXs) in response to developmental cues take place during seed germination. After rice grain milling, the endogenous lipases and LOXs present in the bran fraction come in contact with the storage lipid reserve or triacylglycerol (TAG). Lipases catalyze the hydrolysis of TAGs to non-esterified fatty acids (NEFAs) and glycerol. The NEFAs, especially linoleic acid (18:2) produced, are further subjected to oxidative rancidity via peroxidation reaction catalyzed by LOXs. This results in the production of conjugated hydroperoxides of 18:2 that influence the stale off-flavors in rice bran lipids. The aim of this study is to understand how lipid mobilization and expression of lipase and LOX genes occur in the bran of germinating rice grains (Oryza sativa var. Pusa Basmati 1). Our results show that the primary source of storage lipids in bran is TAG, and its mobilization starts at 4 days after imbibition (4 DAI). Using publically available RNA-seq data and phylogeny analyses, we selected a total of 18 lipase and 16 LOX genes in rice for their expression profiles during onset of lipid mobilization. Gene expression analyses revealed OsLip1, OsLip9, and OsLip13; and OsLOX3 and OsLOX14 as the predominantly expressed genes in bran of germinating rice grains. This study explores two important events in the germinating rice grains, namely, mobilization of storage lipids and expression pattern of lipase and LOX genes. The information generated in this study can be used to efficiently manipulate the genes to enhance the shelf-stability of bran lipid reserve.
Linoleic acid (LA) is the most abundant polyunsaturated fatty acid found in the western diet. Cytochrome P450-derived LA metabolites 9,10-epoxyoctadecenoic acid (9,10-EpOME), 12,13-epoxyoctadecenoic acid (12,13-EpOME), 9,10-dihydroxy-12Z-octadecenoic acid (9,10-DiHOME) and 12,13-dihydroxy-9Z-octadecenoic acid (12,13-DiHOME) have been studied for their association with various disease states and biological functions. Previous studies of the EpOMEs and DiHOMEs have focused on their roles in cytotoxic processes, primarily in the inhibition of the neutrophil respiratory burst. More recent research has suggested the DiHOMEs may be important lipid mediators in pain perception, altered immune response, and brown adipose tissue (BAT) activation by cold and exercise. The purpose of this review is to summarize the current understanding of the physiological and pathophysiological roles and modes of action of the EpOMEs and DiHOMEs in health and disease.
The drastic rise in global warming and the fossil fuel consumption have resulted in destruction of the ecological balance, reduction of the environmental quality, and demotion of the sustainable development. The utilization of biofuels have been paid much attention to by researchers and policy makers due to its benefits and indisputable contributions to protect the living environment. Free fatty acid-rich rice bran oil which is unsuitable for food purposes could be a good candidate for biofuel production. Accordingly, rice bran oil-based biofuels (straight oil and its biodiesel) as promising alternative fuels to petrodiesel were reviewed in this article from the sources, components, and physicochemical perspectives. In addition, biodiesel production from rice bran oil using various methods and catalysts was thoroughly detailed. The oxidative stability of rice bran biodiesel as a function of the storage time was also discussed. The application of rice bran oil-based biofuels to diesel engines was completely analyzed and critically discussed based on engine performance, combustion, and emissions characteristics. The effects of using rice bran oil-based biofuels on the lubricating oil degradation, deposit formation, wear, and sound intensity of diesel engines were explained in detail. Finally, the economic aspects of using rice bran oil and its biodiesel as fuels were also assessed. As a conclusion, the blend containing 20% rice bran oil biodiesel and 80% petrodiesel fuel, both in volume, could be the most effective composition considering the techno-economic aspects of diesel engines; meanwhile the remaining blends appeared to be improper for the existing diesel engines.
The effects of enzymatic free fatty acid reduction process (EFFARP) on the composition and phytochemicals of dewaxed and degummed rice bran oil (DDRBO) were investigated and compared with the effects observed using internal acyl acceptors. The acid value of DDRBO was effectively decreased from 16.99 mg KOH/g to approximately 0.36 mg KOH/g by EFFARP. EFFARP significantly decreased the moisture content and peroxide value of DDRBO and increased the induction period. The Sn-2 fatty acid comoposition of DDRBO after EFFARP was very reaching the total fatty acid composition. EFFARP significantly increased the triacylglycerol content compared to the control, while the oryzanol content was not obviously affected. The contents of free sterol, and total tocopherol and tocotrienol were increased slightly by EFFARP compared to the control. When conducted under vacuum with added nitrogen, EFFARP shows great application potential in the edible oil industry.
Rice bran rancidity may affect rice bran protein through protein oxidation. However, little is known about the relationship between rice bran rancidity and rice bran protein oxidation. The effects of rice bran rancidity on the oxidation extent and structural characteristics of rice bran protein were investigated. As storage time of rice bran increased, the acid value, peroxide value, and value of thiobarbituric acid reactive substances in crude rice bran oil increased from 4.31 mg KOH/g, 2.84 Meq/kg, and 6.22 μg MDA/g to 38.72 mg KOH/g, 15.58 Meq/kg, and 28.99 μg MDA/g, respectively, which indicated that hydrolytic rancidity and oxidative rancidity of rice bran occurred simultaneously. The gradual increase in protein carbonyl and dityrosine content from 2.12 nmol/mg and 88.61 A.U. to 13.8 nmol/mg and 159.37 A.U. was accompanied by a steady decrease in free sulfhydryl content of rice bran protein from 22.6 to 9.6 nmol/mg, which implied that the products of rice bran rancidity induced rice bran protein oxidation. The rice bran protein oxidation subsequently resulted in a loss of the ordered state of secondary structure and the formation of aggregates as well as cross-link, when both disulfide bonds and non-disulfide covalent bonds participated in cross-link formation.
Perilla seed powder (PSP) was stored at 25 °C, 35 °C, and 45 °C for 8 weeks. Changes in the metabolite profiles of the powders, including fatty acids, were monitored. Correlations between these changes and quality parameters, including lipid oxidation, color, and antioxidant activity, were analyzed to evaluate the effects of storage duration and temperature on PSP quality. Acid values increased significantly with the duration of storage, but not with temperature. Multivariate statistical analysis was performed to identify differences among the metabolite profiles. The PSP sample stored for 1 week at 45 °C and all samples stored at 25 °C and 35 °C were grouped separately from the control and samples stored at 45 °C for more than 4 weeks. Among the many metabolites associated with these differences, lysophosphatidylethanolamines, tocopherol, sitosterol, tryptophan, 12-hydroxyjasmonic acid glucoside, and maltose correlated negatively with quality parameters with the exception of L* and antioxidant activity. Luteolin, apigenin, luteolin 4′-methyl ester, citric acid, isocitric acid, 9(S)-HPODE, and 3,5-octadien-2-one correlated positively with quality. Although the quantities of some antioxidants and lipids decreased during storage, the results suggested that the quality of PSP samples stored at 25 °C, 35 °C, and 45 °C for 8 weeks was acceptable. This was because lipid oxidation promoted by the storage environment was limited by antioxidants in the samples. These metabolites could be useful for monitoring changes in PSP quality.
Mutations in the MECP2 gene are the main cause of Rett syndrome (RTT), a pervasive neurodevelopmental disorder, that shows also multisystem disturbances associated with a metabolic component. The aim of this study was to investigate whether an increased production of oxidized linoleic acid metabolites, specifically 9- and 13-hydroxyoctadecadienoic acids (HODEs), can contribute to the altered the redox and immune homeostasis, suggested to be involved in RTT.
Serum levels of 9- and 13-HODEs were elevated in RTT and associated with the expression of arachidonate 15-Lipoxygenase (ALOX15) in peripheral blood mononuclear cells (PBMCs). Omega-3 polyunsaturated fatty acids supplementation has shown to lower HODEs levels in RTT. Statistically significant correlation was demonstrated between the increased plasma HODEs levels and the lipoprotein-associated phospholipase A2 (Lp-PLA2) activity.
Collectively, these findings reinforce the concept of the key role played by lipid peroxidation in RTT, and the possible ability of omega-3 polyunsaturated fatty acids supplementation in improving the oxinflammation status in RTT.
The ultrahigh-performance liquid chromatography-mass spectrometry (UHPLC/MS) method was optimized and validated for the determination of oxylipins in human plasma using the targeted approach with selected reaction monitoring (SRM) in the negative-ion electrospray ionization (ESI) mode. Reversed phase UHPLC separation on an octadecylsilica column enabled the analysis of 63 oxylipins including numerous isomeric species within 12-min run time. The method was validated (calibration curve, linearity, limit of detection, limit of quantification, carry-over, precision, accuracy, recovery rate, and matrix effect) and applied to 40 human female plasma samples from breast cancer patients and age-matched healthy volunteers (control). Thirty-six oxylipins were detected in human plasma with concentrations above the limit of detection, and 21 of them were quantified with concentrations above the limit of quantitation. The concentrations determined in healthy controls are in a good agreement with previously reported data on human plasma. Quantitative data were statistically evaluated by multivariate data analysis (MDA) methods including principal component analysis (PCA) and orthogonal partial least square discriminant analysis (OPLS-DA). S-plot and box plots showed that 13-HODE, 9-HODE, 13-HOTrE, 9-HOTrE, and 12-HHTrE were the most upregulated oxylipin species in plasma of breast cancer patients.
Tea seed oil is unique to Asia and boasts significant nutritional and health benefits. In this study, the volatile components of tea seed oil from eight major producing areas in China were analysed using HS-SPME-GC/MS. The comparison was made among them to obtain their characteristic volatile compounds. After fibre selection and extraction and desorption condition optimisation, 194 types of volatile components, mainly consisting of aldehydes, pyrazines and esters, were detected. Three principle components were obtained by principal component analysis (PCA), allowing the different cultivars of tea seed oil to be characterised with strong correlation coefficients between factors. Both cluster discriminant analysis and PCA showed that geographical regions could influence the composition and content of tea seed oil's volatile components.
Rice bran is a by-product of rice milling industry and constitutes around 10% of the total weight of rough rice. It is primarily composed of aleurone, pericarp, subaleurone layer and germ. Rice bran is a rich source of vitamins, minerals, essential fatty acids, dietary fibre and other sterols. There is a widespread scientific agreement on various health benefits associated with consumption of dietary fibre. Consumer attitude towards health foods is promising and the scope of functional foods is growing in the world markets; rice bran is finding increased applications in food, nutraceutical and pharmaceutical industries. However, potential applications of rice bran in food industry are limited by its instability owing to rancidity caused by exposure of oil to lipases during milling. Various methods of stabilization have been carried out, paving way for supplementation of rice bran in numerous food preparations. Considering the importance of rice bran, this review aims to focus on the functionalities of rice bran, its health benefits and potential applications in food industry.
Lipases are important biocatalysts showing many interesting properties with industrial applications. Previously, different isoforms of lipases, Lipase-I and Lipase-II from rice (Oryza sativa) have been purified and characterized. Lipase-II identified as the major lipase in rice bran is designated as rice bran lipase (RBL). In this study, we report the cloning and expression of the RBL in E. coli and Pichia pastoris. An exploration of expression in four different E. coli expression systems analysed: BL21(DE3)pLysS, RIL(DE3)pLysS, Rosetta(DE3)pLysS and Origami(DE3)pLysS indicated that E. coli was not a suitable host. Expression with supplement of rare codons in Rosetta (DE3)pLysS and RIL(DE3)pLysS resulted in highest expression as insoluble inclusion bodies. The hurdles of expression in E. coli were overcome by expression as a secretory protein in Pichia pastoris X-33. The expression of lipase in shake flasks was optimized to achieve the maximum recombinant lipase activity of 152.6 U/mL. The purified recombinant lipase had a specific activity of 998 U/mg toward triacetin. The pH and temperature optimum of native and recombinant enzymes were pH 7.4 and 25 ± 2 °C respectively. Both the lipases showed higher activity toward short chain triacylglycerol and unsaturated fatty acid enriched oils. Computational modelling and molecular docking studies reveal that the catalytic efficiency of the lipase correlates with the distance of the nucleophilic Ser(175)-OH and the scissile ester bond. The shorter the distance, the greater is the turnover of the substrate.
Tripalmitin-enriched triacylglycerols were concentrated from palm stearin by acetone fractionation and as the substrate reacted with a mixture of equimolar quantities of fatty acids (C8:0-C18:3). The incorporation degree and acyl migration level of the fatty acids and acylglycerols composition were investigated, providing helpful information for the production of human milk fat substitutes. Higher incorporation degrees of the fatty acids were obtained with lipase PS IM, Lipozyme TL IM, and Lipozyme RM IM followed by porcine pancreatic lipase and Novozym 435-catalyzed acidolysis. During reactions catalyzed by Lipozyme TL IM, Lipozyme RM IM, and lipase PS IM, incorporation degrees of C12:0, C14:0, C18:1, and C18:2 were higher than those of other fatty acids at operated variables (molar ratio, temperature, and time), and the triacylglycerols content reached the highest (82.09%) via Lipozyme RM IM-catalyzed acidolysis. On the basis of significantly different levels of acyl migration to the sn-2 position, lipases were in the order of lipase PS IM < Lipozyme TL IM < Lipozyme RM IM.
The cuticle covers the aerial portions of land plants. It consists of amorphous intracuticular wax embedded in cutin polymer, and epicuticular wax crystalloids that coat the outer plant surface and impart a whitish appearance. Cuticular wax is mainly composed of long-chain aliphatic compounds derived from very long chain fatty acids. Wax biosynthesis begins with fatty acid synthesis in the plastid. Here we focus on fatty acid elongation (FAE) to very long chains (C24-C34), and the subsequent processing of these elongated products into alkanes, secondary alcohols, ketones, primary alcohols and wax esters. The identity of the gene products involved in these processes is starting to emerge. Other areas of this field remain enigmatic. For example, it is not known how the hydrophobic wax components are moved intracellularly, how they are exported out of the cell, or translocated through the hydrophilic cell wall. Two hypotheses are presented for intracellular wax transport: direct transfer of lipids from the endoplasmic reticulum to the plasma membrane, and Golgi mediated exocytosis. The potential roles of ABC transporters and non-specific lipid transfer proteins in wax export are also discussed. Biochemical-genetic and genomic approaches in Arabidopsis thaliana promise to be particularly useful in identifying and characterizing gene products involved in wax biosynthesis, secretion and function. The current review will, therefore, focus on Arabidopsis as a model for studying these processes.
Alzheimer's disease (AD) is a neurological disorder that has a considerable impact on the health of the elderly. Although oxidative stress has been implicated in the early stage of this disease, its detailed pathogenesis and therapeutic targets remain unknown. The diagnosis, particularly at the early stage, is important. In the present study, the levels of potential biomarkers such as total hydroxyoctadecadienoic acid (tHODE) and oxidatively modified peroxiredoxin (oxPrx)-2 and oxPrx-6 in plasma and/or erythrocytes were determined by a GC-MS apparatus and by two-dimensional electrophoresis, respectively. It was found that these levels in AD patients were significantly higher than those in the healthy controls. Furthermore, the tHODE levels increased with increasing clinical dementia ratings. Interestingly, vascular dementia patients could be distinguished by the correlation between plasma and erythrocyte tHODE levels or by that of tHODE with oxPrx in erythrocytes. These data further support that oxidative stress is indeed involved in AD and that the correlative measures of tHODE and oxPrx are potential biomarkers for its diagnosis.