Exogenous oxidized phytosterol may modulate linoleic acid metabolism through upregulation of fatty acid desaturase in rats

Previous in vitro studies have indicated that oxidized phytosterol (OPS) exhibits some toxicity; however, the harmful effects of OPS on fatty acid metabolism are not completely understood yet. Therefore, this study examined the effects of exogenous phytosterol (PS) and OPS on growth parameters and lipid metabolism in rats. Rats were provided with AIN-76 basal diet, basal diet +0.5% PS, or basal diet +0.5% OPS. We found that the level of cholesterol and triacylglycerols in the liver was significantly lower in OPS-fed rats than in basal diet-fed rats. The ratio of Δ6 desaturation index (20:3(n-6) + 20:4(n-6))/18:2(n-6) in the plasma was significantly higher in the OPS-fed rats than in the PS-fed rats. Additionally, the proportion of arachidonic acid (20:4) in the liver was significantly higher in the OPS-fed group compared with the control group. The mRNA expression levels of Δ6 and Δ5 desaturases were significantly higher in OPS-fed rats than in basal diet-fed rats, but remained unchanged in PS-fed rats. Moreover, the protein level of Δ6 desaturase was significantly higher in both PS- and OPS-fed rats compared with basal diet-fed rats, while the protein level of Δ5 desaturase tended to be higher only in OPS-fed rats than in basal diet-fed rats. Thus, exogenous OPS, but not PS, altered fatty acid composition through the upregulation of mRNA and protein levels of fatty acid desaturation enzymes in the liver. This indicates that exogenous OPS, unlike PS, may modulate the production of eicosanoids from arachidonic acid, potentially promoting allergic reactions, inflammation, and atherosclerosis.

Influence of ozone treatment on sensory quality, aroma active compounds, phytosterols and phytosterol oxidation products in stored rapeseed and flaxseed oils

The effect of ozone treatment on the sensory quality, aroma compounds, phytosterols, and phytosterol oxidation products (POP) in stored plant oils was studied. Cold-pressed flaxseed, cold-pressed rapeseed, and refined rapeseed oils were treated with ozone, air, and nitrogen, then subjected to accelerated storage at 60 °C for 6 days. The sensory evaluation revealed that ozone significantly influenced the sensory profile, with notable cucumber and green-grassy aromas. Quantitation of odorants determined by headspace SPME-GC/MS and calculation of odor activity values (OAV) identified nonanal (citrus-like, soapy aroma, OAV 356), (E,Z)-2,6-nonadienal (cucumber aroma, OAV 312), (Z)-3-hexenal (green grassy aroma, OAV 326), and hexanal (green grassy aroma, OAV 163) as major odorants. Furthermore, ozonation reduced total sterol content in refined rapeseed oil by 48 % during storage. While ozone did not form POP initially, they were produced during storage, with the most significant impact on rapeseed oil, doubling POP content compared to air and nitrogen treatments.

Stigmasterol and its esters encapsulated in liposomes: Characterization, stability, and derivative formation

Dipalmitoylphosphatidylcholine liposomes were encapsulated with free stigmasterol (ST), stigmasteryl myristate (ME), and stigmasteryl oleate (OE). Their quality was determined using TEM, FT-IR spectroscopy, zeta potential and hydrodynamic diameter. The prepared liposomes were heated at 60 and 180 °C. The degradation of stigmasterol, fatty acids was determined, as was the formation of derivatives. The results show that the liposomes had been prepared successfully. The ST liposomes were the smallest, while the ME and OE liposomes were of similar size. The extent to which the compounds encapsulated in the liposomes degraded depended on their structure. When samples were heated to 60 °C, the degradation of stigmasterol ranged from 11 % in ST to 47 % in OE and 58 % in ME. After heating to 180 °C, the lowest level of degradation of stigmasterol was for OE (51 %), whereas the degradation of stigmasterol in ST and ME was 85 % and 90 %, respectively. In addition, the high level of oxyphytosterols in the samples heated to 180 °C is of concern, especially in the ST and ME samples. The level of SOP in liposomes heated to 60 °C ranged from 1.7 mg/g in liposomes encapsulated with free stigmasterol to 10.4 and 32.9 mg/g in liposomes with stigmasteryl myristate and oleate. After heating to 180 °C, the total content of SOP was much higher, ranging from 68.2 for OE to 111.7 and 135.7 mg/g for ME and ST, respectively.

Treatment with β-sitosterol ameliorates the effects of cerebral ischemia/reperfusion injury by suppressing cholesterol overload, endoplasmic reticulum stress, and apoptosis

β-Sitosterol is a type of phytosterol that occurs naturally in plants. Previous studies have shown that it has anti-oxidant, anti-hyperlipidemic, anti-inflammatory, immunomodulatory, and anti-tumor effects, but it is unknown whether β-sitosterol treatment reduces the effects of ischemic stroke. Here we found that, in a mouse model of ischemic stroke induced by middle cerebral artery occlusion, β-sitosterol reduced the volume of cerebral infarction and brain edema, reduced neuronal apoptosis in brain tissue, and alleviated neurological dysfunction; moreover, β-sitosterol increased the activity of oxygen- and glucose-deprived cerebral cortex neurons and reduced apoptosis. Further investigation showed that the neuroprotective effects of β-sitosterol may be related to inhibition of endoplasmic reticulum stress caused by intracellular cholesterol accumulation after ischemic stroke. In addition, β-sitosterol showed high affinity for NPC1L1, a key transporter of cholesterol, and antagonized its activity. In conclusion, β-sitosterol may help treat ischemic stroke by inhibiting neuronal intracellular cholesterol overload/endoplasmic reticulum stress/apoptosis signaling pathways.

Gas chromatography ion mobility spectroscopy: A rapid and effective tool for monitoring oil oxidation

Oil autoxidation is an early process of food deterioration, monitoring oil oxidation is therefore of great significance to ensure food quality and safety. In this study, a detection method of the primary and secondary oxidative products was developed by gas chromatography ion mobility spectrometry (GC-IMS).The secondary oxidative products was analyzed by GC-IMS. Then, the relationships between peroxide values and the contents of secondary oxidative products were investigated by constructing a prediction model of peroxide value of rapeseed oil with the help of secondary oxidative products and chemometrics. The coefficient of determination Q2 of the model validation set is 0.96, and the RMSECV is 0.1570 g/100 g. These validation results indicated that secondary oxidative products could also reflect the content of the primary oxidative products. Moreover, 10 characteristic markers related to oxidative rancidity were identified for monitoring edible oil rancidity and oxidative stability.

Anti-proliferative potential and oxidative reactivity of thermo-oxidative degradation products of stigmasterol and stigmasteryl esters for human intestinal cells

Stigmasterol in free and esterified form is incorporated in LDL cholesterol-lowering food products, intended for direct consumption and cooking, baking, and frying. Under thermal treatment, stigmasterol compounds may constitute a source of thermo-oxidative degradation products and oxyderivatives with potentially adverse health effects. This study aimed to analyze the anti-proliferative potential and genotoxicity of thermo-oxidatively treated stigmasterol (ST), stigmasteryl linoleate (ST-LA), and oleate (ST-OA). The effects on cell viability and proliferation, cell cycle progression, intracellular reactive oxygen species (ROS) generation, and DNA damage were analyzed in normal human intestinal cells. The mutagenic potential was assessed in a bacterial reverse mutation test using Salmonella enterica serovar Typhimurium strains involving metabolic activation. Stigmasteryl esters showed a significantly lower potential to affect intestinal cell viability and proliferation than non-esterified ST, regardless of heating. Thermo-oxidatively treated ST suppressed intestinal cell proliferation by arresting the cell cycle in the G₂/M phase and DNA synthesis inhibition. The enhanced intracellular ROS generation and caspase 3/7 activity suggest targeting intestinal cells to the apoptosis pathway. Also, heated ST-LA intensified ROS production and elicited pro-apoptotic effects. Thermo-oxidative derivatives of ST and ST-LA may evoke harmful gastrointestinal effects due to their high oxidative reactivity towards intestinal cells.

Thermo-oxidative stability of asymmetric distigmasterol-modified acylglycerols as novel derivatives of plant sterols

The study investigated the thermo-oxidative stability of distigmasterol-modified acylglycerols as a new structured acylglycerols. Samples were heated at 60 and 180 °C for 8 h. Their percentage degradation and products formed during heating were compared with free stigmasterol and stigmasteryl esters. The remaining of stigmasterol and fatty acid parts, the formation of stigmasterol oxidation products and the composition of polar and non-polar fractions were analysed using chromatographic methods. The cytotoxicity and genotoxicity were determined with the use of an MTT test and a comet assay, respectively. The highest stability during heating was observed for 2,3-distigmasterylsuccinoyl-1-oleoyl-sn-glycerol (dStigS-OA) and the lowest for 2,3-distigmasterylcarbonoyl-1-oleoyl-sn-glycerol (dStigC-OA). Data showed that the formation of thermo-oxidative degradation products is affected by the temperature and chemical structure of lipids present in the molecule. The dStigMAs bonded by a succinate linker and products formed during their thermo-oxidation showed no cytotoxic or genotoxic activity to normal human cells.

Determination of phytosterol oxidation products in pharmaceutical liposomal formulations and plant vegetable oil extracts using novel fast liquid chromatography - Tandem mass spectrometric methods

Phytosterol oxidation products (POPs) formed by the auto-oxidation of phytosterols can lead to negative health consequences. New liquid chromatography-tandem mass spectrometry (LC-MS/MS) quantitative and qualitative approaches were developed. For quantification, sixteen phytosterol oxidation products (POPs) in liposomal formulations; namely 7-keto, 7-hydroxy, 5,6-epoxy, and 5,6-dihydroxy derivatives of brassicasterol, campesterol, stigmasterol, and β-sitosterol were quantified. The method has a short run time of 5 min, achieved on a poroshell C18 column, using isocratic elution. To the best of our knowledge, this is the shortest run time among reported methods for the quantitative analysis of POPs. Atmospheric pressure chemical ionization (APCI) was used, and the mobile phase was composed of acetonitrile/methanol (99:1 v/v). The quantitative method was validated as per the FDA guidelines for linearity, accuracy, precision, selectivity, sensitivity, matrix effect, dilution integrity, and stability. The method was applied for the quantification of POPs in liposomal phytosterol formulations prepared with and without tocopherols, as antioxidants. The formulation process had little impact on the formation of POPs as only 7-ketobrassicasterol was quantified in tested samples. The quantified value of POPs in liposomal samples was insignificant to impart any toxicological effects. Other degradation products such as 7-hydroxy, 5,6-epoxy and 5,6-dihydroxy derivatives of brassicasterol, campesterol and β-sitosterol were below the lower limit of quantification. Phytosterol-containing formulations were then assessed for their oxidative stability after microwave exposure for 5 min. The incorporation of tocopherols significantly increased the stability of phytosterols in the liposomal formulations. Finally, LC-MS/MS qualitative identification of phytosterols obtained from extra virgin olive oil was performed. New POPs, namely 7-ketoavenasterol, and 7-ketomethylenecycloartenol were putatively identified, illustrating the applicability of the method to identify POPs with varying structures present in various phytosterol sources. In fact, it is the first time that 7-ketomethylenecycloartenol is reported as a POP.

Phytosterols: Potential Metabolic Modulators in Neurodegenerative Diseases

Phytosterols constitute a class of natural products that are an important component of diet and have vast applications in foods, cosmetics, and herbal medicines. With many and diverse isolated structures in nature, they exhibit a broad range of biological and pharmacological activities. Among over 200 types of phytosterols, stigmasterol and β-sitosterol were ubiquitous in many plant species, exhibiting important aspects of activities related to neurodegenerative diseases. Hence, this mini-review presented an overview of the reported studies on selected phytosterols related to neurodegenerative diseases. It covered the major phytosterols based on biosynthetic considerations, including other phytosterols with significant in vitro and in vivo biological activities.

β-sitosterol induces reactive oxygen species-mediated apoptosis in human hepatocellular carcinoma cell line

Objective:

It is of interest to investigate the anti-proliferative effect of β-sitosterol (BS) on human hepatocellular carcinoma (HepG2) cell line.

Materials and Methods:

β-sitosterol treatments (0.6 and 1.2 mM/ml) were done in HepG2 and after 24 hr, cell viability was evaluated by MTT assay. Reactive oxygen species (ROS) accumulating potential of BS was assessed by dichloro-dihydro-fluorescein diacetate staining. Morphology related to apoptosis was investigated by acridine orange and ethidium bromide dual staining. Cytochrome c and caspase 3 expressions were evaluated by immunofluorescence and western blot analyses.

Results:

β-sitosterol induced cytotoxicity (p<0.001) and intracellular ROS in HepG2 cells in a dose-dependent manner. BS treatments accumulated induced intracellular ROS accumulation which led to membrane damage and mitochondrial toxicity. At the molecular level, BS treatments induced cytochrome c release from mitochondria and enhanced the protein expressions (p<0.05 vs 0.6 mM/ml and p<0.001 vs 1.2 mM/ml) of both caspase 3 and cleaved caspase 3.

Conclusion:

β-sitosterol induced ROS accumulation which plays a critical role in apoptosis via the intrinsic pathway in HepG2 cells. The present investigation paves the way for further in vivo studies.

Sterols and Sterol Oxidation Products: Effect of Dietary Intake on Tissue Distribution in ApoE-Deficient Mice

Sterols and sterol oxidation products (SOPs) are well-known dietary factors influencing atherosclerosis; however, their distribution in vivo after dietary sterol/SOP intake is still unclear. Here, we investigated the tissue distribution of sterols and SOPs in ApoE^-/- mice after dietary exposure to diets supplemented with phytosterols (PS), phytosterol oxidation products (POPs), or cholesterol oxidation products (COPs). The results showed that PS intake reduced cholesterol in serum and the liver but increased cholesterol in the brain. PS intake increased the levels of PS in vivo and the levels of 7-keto- and triol-POPs in serum and the liver. COP intake elevated the level of all COPs in serum but did not change the 7-keto-cholesterol level in the liver and brain. All POPs in serum and parts of POPs in the liver and brain increased after dietary POP exposure. Our study indicated that dietary PS and SOPs accumulated in vivo with varying degrees and influenced cerebral cholesterol metabolism.

Linking phytosterols and oxyphytosterols from food to brain health: origins, effects, and underlying mechanisms

Phytosterols and their oxidation products, namely oxyphytosterols, are natural compounds present in plant foods. With increased intake of phytosterol-enriched functional food products, the exposure of both phytosterols and oxyphytosterols is rising. Over the past ten years, researches have been focused on their absorption and metabolism in human body, as well as their biological effects. More importantly, recent studies showed that phytosterols and oxyphytosterols can traverse the blood-brain barrier and accumulate in the brain. As brain health problems resulting from ageing being more serious, attenuating central nervous system (CNS) disorders with active compounds in food are becoming a hot topic. Phytosterols and oxyphytosterols have been shown to implicated in cognition altering and the pathologies of several CNS disorders, including Alzheimer's disease and multiple sclerosis. We will overview these findings with a focus on the contents of phytosterols and oxyphytosterols in food and their dietary intake, as well as their origins in the brain, and illustrate molecular pathways through which they affect brain health, in terms of inflammation, cholesterol homeostasis, oxidative stress, and mitochondria function. The existing scientific gaps of phytosterols and oxyphytosterols to brain health in knowledge are also discussed, highlighting research directions in the future.

Safety of the extension of use of plant sterol esters as a novel food pursuant to Regulation (EU) 2015/2283

Following a request from the European Commission, the EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA) was asked to deliver an opinion on the safety of an extension of use of the novel food 'plant sterol esters' when added to vegetable fat spreads and to liquid vegetable fat-based emulsions for cooking and baking purposes pursuant to Regulation (EU) 2015/2283. Member States expressed concerns in relation to plant sterol oxidation products (POP) and consumption by non-target population groups. The median (0.5%) and P90 (2.28%) value of the oxidation rates of plant sterols determined by a wide range of cooking experiments were used together with exposure estimates for plant sterol when added and cooked with vegetable fat spreads and liquids. The no-observed adverse effect level (NOAEL) of a subchronic rat study and an applied default uncertainty factor of 200 served to derive levels (i.e. 0.64 mg POP/kg body weight (bw) per day) considered safe for humans. This safe level of exposure would be exceeded at the P95 by all age groups when considering the P90 oxidation rate and using EFSA's comprehensive food consumption database for assessing the potential exposure. When considering the median oxidation rate, the safe level of 0.64 mg POP/kg bw per day would be exceeded at the highest P95 intake estimates in children below 9 years of age. When considering an intake of the maximum authorised use level of 3 g plant sterols/person per day and oxidation rates of 0.5% and 2.28%, the resulting daily POP intakes per kg bw by an adult weighing 70 kg would be 0.21 and 0.98 mg/kg bw per day, respectively, the latter value exceeding 0.64 mg/kg bw per day. The Panel concludes that the safety of the intended extension of use of plant sterol esters under the proposed conditions of use has not been established.

The Impact of Phytosterols on the Healthy and Diseased Brain

The central nervous system (CNS) is the most cholesterol-rich organ in mammals. Cholesterol homeostasis is essential for proper brain functioning and dysregulation of cholesterol metabolism can lead to neurological problems. Multiple sclerosis (MS) and Alzheimer's disease (AD) are examples of neurological diseases that are characterized by a disturbed cholesterol metabolism. Phytosterols (PS) are plant-derived components that structurally and functionally resemble cholesterol. PS are known for their cholesterol-lowering properties. Due to their ability to reach the brain, researchers have started to investigate the physiological role of PS in the CNS. In this review, the metabolism and function of PS in the diseased and healthy CNS are discussed.

Endothelial dysfunction and vascular disease - a 30th anniversary update

The endothelium can evoke relaxations of the underlying vascular smooth muscle, by releasing vasodilator substances. The best-characterized endothelium-derived relaxing factor (EDRF) is nitric oxide (NO) which activates soluble guanylyl cyclase in the vascular smooth muscle cells, with the production of cyclic guanosine monophosphate (cGMP) initiating relaxation. The endothelial cells also evoke hyperpolarization of the cell membrane of vascular smooth muscle (endothelium-dependent hyperpolarizations, EDH-mediated responses). As regards the latter, hydrogen peroxide (H₂ O₂ ) now appears to play a dominant role. Endothelium-dependent relaxations involve both pertussis toxin-sensitive G_i (e.g. responses to α₂ -adrenergic agonists, serotonin, and thrombin) and pertussis toxin-insensitive G_q (e.g. adenosine diphosphate and bradykinin) coupling proteins. New stimulators (e.g. insulin, adiponectin) of the release of EDRFs have emerged. In recent years, evidence has also accumulated, confirming that the release of NO by the endothelial cell can chronically be upregulated (e.g. by oestrogens, exercise and dietary factors) and downregulated (e.g. oxidative stress, smoking, pollution and oxidized low-density lipoproteins) and that it is reduced with ageing and in the course of vascular disease (e.g. diabetes and hypertension). Arteries covered with regenerated endothelium (e.g. following angioplasty) selectively lose the pertussis toxin-sensitive pathway for NO release which favours vasospasm, thrombosis, penetration of macrophages, cellular growth and the inflammatory reaction leading to atherosclerosis. In addition to the release of NO (and EDH, in particular those due to H₂ O₂ ), endothelial cells also can evoke contraction of the underlying vascular smooth muscle cells by releasing endothelium-derived contracting factors. Recent evidence confirms that most endothelium-dependent acute increases in contractile force are due to the formation of vasoconstrictor prostanoids (endoperoxides and prostacyclin) which activate TP receptors of the vascular smooth muscle cells and that prostacyclin plays a key role in such responses. Endothelium-dependent contractions are exacerbated when the production of nitric oxide is impaired (e.g. by oxidative stress, ageing, spontaneous hypertension and diabetes). They contribute to the blunting of endothelium-dependent vasodilatations in aged subjects and essential hypertensive and diabetic patients. In addition, recent data confirm that the release of endothelin-1 can contribute to endothelial dysfunction and that the peptide appears to be an important contributor to vascular dysfunction. Finally, it has become clear that nitric oxide itself, under certain conditions (e.g. hypoxia), can cause biased activation of soluble guanylyl cyclase leading to the production of cyclic inosine monophosphate (cIMP) rather than cGMP and hence causes contraction rather than relaxation of the underlying vascular smooth muscle.

On-line liquid chromatography-gas chromatography: A novel approach for the analysis of phytosterol oxidation products in enriched foods

A novel methodology for the automated qualitative and quantitative determination of phytosterol oxidation products in enriched foods via on-line liquid chromatography-gas chromatography (LC-GC) was established. The approach is based on the LC pre-separation of acetylated phytosterols and their corresponding oxides using silica as stationary phase and a mixture of n-hexane/methyl tert-butyl ether/isopropanol as eluent. Two LC-fractions containing (i) 5,6-epoxy- and 7-hydroxyphytosterols, and (ii) 7-ketophytosterols are transferred on-line to the GC for the analysis of their individual compositions on a medium polar trifluoropropylmethyl polysiloxane capillary column. Thus, conventionally employed laborious off-line purification and enrichment steps can be avoided. Validation data, including recovery, repeatability, and reproducibility of the method, were elaborated using an enriched margarine as example. The margarine was subjected to a heating procedure in order to exemplarily monitor the formation of phytosterol oxidation products. Quantification was performed using on-line LC-GC-FID, identification of the analytes was based on on-line LC-GC-MS. The developed approach offers a new possibility for the reliable and fast analysis of phytosterol oxidation products in enriched foods.

Phytochemical and biological studies of Butia capitata Becc. leaves cultivated in Egypt

OBJECTIVE

To study the antioxidant and anti-inflammatory activity of Butia capitata (B. capitata) leaf extracts along with phytochemical analysis of the proposed bioactive constituents.

METHODS

Different successive extracts of B. capitata Becc. leaves were prepared with selective organic solvents and screened for their anti-inflammatory activities in tested animals and in-vitro antioxidant effect. An extensive phytochemical investigation of the bioactive extracts through paper chromatography, thin layer chromatography, column chromatography, gas-liquid chromatography (GLC), high pressure liquid chromatography and spectral analysis. GC-Mass, ultraviolet, hydrogen and carbon nuclear magnetic resonance, electron ionization-mass spectrometry, heteronuclear multiple bond correlation and heteronuclear multiple quantum correlation were carried out.

RESULTS

Results showed that different extracts possess promising antioxidant effect and significant anti-inflammatory activity with variable degrees. The results of the phytochemical investigation of the bioactive extracts revealed the presence of volatile substances, lipoidal matter, α-tocopherol, free sugars, polysaccharides and flavonoidal compounds.

CONCLUSIONS

B. capitata leaf extracts were shown to possess variable antioxidant effect, the most promising was methanol extract. Both polar and non polar extracts were proved to have anti-inflammatory activity, the non polar extract was superior in this respect. The bioactivity of the extracts was ascribed to the presence of flavonoids, sterols and α-tocopherol.