Antioxidant/prooxidant effects of dietary non-flavonoid phenols on the Cu2+-induced oxidation of human low-density lipoprotein (LDL)

Exploiting the beneficial effects of Salvia officinalis L. extracts in human health and assessing their activity as potent functional regulators of food microbiota

Salvia officinalis L. has attracted scientific and industrial interest due to its pharmacological properties. However, its detailed phytochemical profile and its correlation with beneficial effects in the human microbiome and oxidative stress remained elusive. To unveil this, S. officinalis was collected from the region of Epirus and its molecular identity was verified with DNA barcoding. Phytochemical profile for both aqueous and ethanol-based extracts was determined by high-pressure liquid chromatography-tandem mass spectrometry and 103 phytochemicals were determined. The effect of S. officinalis extracts as functional regulators of food microbiota by stimulating the growth of Lacticaseibacillus rhamnosus strains and by suppressing evolution of pathogenic bacteria was verified. Furthermore, we recorded that both extracts exhibited a significant cellular protection against H2O2-induced DNA damage. Finally, both extracts exhibited strong inhibitory effect towards LDL oxidation. This study provides a comprehensive characterization of S. officinalis on its phytochemical components as also its potential impact in human microbiome and oxidative stress.

Antioxidant Effects of a Hydroxytyrosol-Based Pharmaceutical Formulation on Body Composition, Metabolic State, and Gene Expression: A Randomized Double-Blinded, Placebo-Controlled Crossover Trial

Hydroxytyrosol (HT) plays a significant role in cardiovascular disease (CVD) protection, and its metabolites are able to protect from the endothelial dysfunction commonly present in atherosclerosis. This randomized double-blinded, placebo-controlled crossover trial determined the effect in healthy volunteers of two gastroresistant capsules containing 15 mg/day of HT, for a 3-week period (HTT). Evaluation of nutritional status, serum metabolites, oxidative stress biomarkers, and gene expression of 9 genes related to oxidative stress, inflammation, and CVDs was performed. Oxidation biomarkers like thiol group (p = 0.001), total antioxidant status (TAS) (p = 0.001), superoxide dismutase 1 (SOD1) (2^-ΔΔCt = 3.7), and plasma concentration of HT (2.83 μg·mL^-1) were significantly increased, while nitrite (p = 0.001), nitrate (p = 0.001), and malondialdehyde (MDA) (p = 0.02) were drastically reduced after HTT. A significant reduction of body fat mass percentage (p = 0.01), suprailiac skinfold (p = 0.01), and weight (p = 0.04; Δ% = -0.46%) was observed after HTT. This study shows that regular intake of 15 mg/day of HT changed body composition parameters and modulated the antioxidant profile and the expression of inflammation and oxidative stress-related genes. However, it is advisable to personalize HT doses in order to exert its health benefits in CVD prevention and protection of LDL-C particles from oxidative damage. This trial is registered with ClinicalTrials.gov NCT01890070.

Hydroxytyrosol in the Prevention of the Metabolic Syndrome and Related Disorders

Virgin olive oil (VOO) constitutes the main source of fat in the Mediterranean diet. VOO is rich in oleic acid, displaying health-promoting properties, but also contains minor bioactive components, especially phenolic compounds. Hydroxytyrosol (HT), the main polyphenol of olive oil, has been reported to be the most bioactive component. This review aims to compile the results of clinical, animal and cell culture studies evaluating the effects of HT on the features of Metabolic Syndrome (MetS) (body weight/adiposity, dyslipidemia, hypertension, and hyperglycemia/insulin resistance) and associated complications (oxidative stress and inflammation). HT was able to improve the lipid profile, glycaemia, and insulin sensitivity, and counteract oxidative and inflammatory processes. Experimental studies identified multiple molecular targets for HT conferring its beneficial effect on health in spite of its low bioavailability. However, rodent experiments and clinical trials with pure HT at biologically relevant concentrations are still lacking. Moreover, the roles of intestine and its gut microbiota have not been elucidated.

Preexposure to Olive Oil Polyphenols Extract Increases Oxidative Load and Improves Liver Mass Restoration after Hepatectomy in Mice via Stress-Sensitive Genes

Polyphenols can act as oxidants in some conditions, inducing redox-sensitive genes. We investigated the effect of preexposure to the olive oil polyphenols extract (PFE) on time-dependent changes in the hepatic oxidative state in a model of liver regeneration—a process in which oxidative stress associated with the metabolic overload accounts for the early events that contribute to the onset of liver self-repair. Liver regeneration was induced by one-third hepatectomy in mice. Prior to hepatectomy, mice were intraperitoneally given either PFE (50 mg/kg body weight) or saline for seven consecutive days, while respective controls received vehicle alone. Redox state-regulating enzymes and thiol proteins along with the mRNA levels of Nrf2 gene and its targets γ-glutamylcysteine synthetase and heme oxygenase-1 were determined at different time intervals after hepatectomy. The liver mass restoration was calculated to assess hepatic regeneration. The resulting data demonstrate the effectiveness of preexposure to PFE in stimulating liver regeneration in a model of a small tissue loss which may be ascribed to the transient increase in oxidant load during the first hours after hepatectomy and associated induction of stress response gene-profiles under the control of Nrf2.

Inhibition of cytotoxicity of Shiga toxin of Escherichia coli O157:H7 on vero cells by Prosopis alba Griseb (Fabaceae) and Ziziphus mistol Griseb (Rhamnaceae) extracts

The capacity of Prosopis alba Griseb. and Ziziphus mistol Griseb. fruit extracts to inhibit the toxic action of Shiga toxin (Stx) was investigated. Purification of Stx from Escherichia coli O157:H7 was performed by saline precipitation and affinity chromatography using a column with globotriaosylceramide, while the fruits were subjected to ethanolic or aqueous extractions. The protective action of both fruits was determined by pre-, co-, and postincubation of one 50% cytotoxic dose per ml of Stx with different concentrations of ethanolic and aqueous extracts in confluent monolayers of Vero cells for 72 h at 37°C (5% CO2). The inhibition of the cytotoxic effect of Stx by fruit extracts was determined by the neutral red vital staining technique. The extraction of the polyphenols and flavonoids was effective, and more polyphenols per milligram of dissolved solids were obtained from P. alba than from Z. mistol. However, there were more flavonoids in Z. mistol than in P. alba. Components of both fruits increased the viability of cells treated with Stx when the extracts were preincubated with Stx for 1 h before being applied to the cell cultures, with the ethanolic extract of P. alba showing 95% cell viability at a concentration of 2.45 mg/ml. The extracts were less effective in protecting cells when Stx, extracts, and cells were coincubated together without a previous incubation of Stx; only the concentrations of 19.46 mg/ml for the P. alba aqueous extract and 3.75 mg/ml for the Z. mistol ethanolic extract resulted in the inhibition of cytotoxicity, with 52 and 56% cell viability occurring, respectively. Investigation into this difference in the protection of cells indicated that the protein molecule of Stx suffered degradation to advanced oxidative protein products during preincubation with extracts, principally with P. alba, which exhibited a greater amount of nonflavonoid polyphenols than Z. mistol. The prooxidant action on Stx favored the cells and enhanced the protective action of both fruits.

Plant-derived phenolics inhibit the accrual of structurally characterised protein and lipid oxidative modifications

Epidemiological data suggest that plant-derived phenolics beneficial effects include an inhibition of LDL oxidation. After applying a screening method based on 2,4-dinitrophenyl hydrazine-protein carbonyl reaction to 21 different plant-derived phenolic acids, we selected the most antioxidant ones. Their effect was assessed in 5 different oxidation systems, as well as in other model proteins. Mass-spectrometry was then used, evidencing a heterogeneous effect on the accumulation of the structurally characterized protein carbonyl glutamic and aminoadipic semialdehydes as well as for malondialdehyde-lysine in LDL apoprotein. After TOF based lipidomics, we identified the most abundant differential lipids in Cu(++)-incubated LDL as 1-palmitoyllysophosphatidylcholine and 1-stearoyl-sn-glycero-3-phosphocholine. Most of selected phenolic compounds prevented the accumulation of those phospholipids and the cellular impairment induced by oxidized LDL. Finally, to validate these effects in vivo, we evaluated the effect of the intake of a phenolic-enriched extract in plasma protein and lipid modifications in a well-established model of atherosclerosis (diet-induced hypercholesterolemia in hamsters). This showed that a dietary supplement with a phenolic-enriched extract diminished plasma protein oxidative and lipid damage. Globally, these data show structural basis of antioxidant properties of plant-derived phenolic acids in protein oxidation that may be relevant for the health-promoting effects of its dietary intake.

Antioxidant, anti-inflammatory, and anti-senescence activities of a phlorotannin-rich natural extract from brown seaweed Ascophyllum nodosum

Aging at the cellular level is characterized by oxidative stress, inflammation, and cell senescence. An extract of the brown seaweed Ascophyllum nodosum rich in phlorotannins has been studied for its inhibitory activity against oxidative stress, inflammation, and senescence. A. nodosum extract at 0.2 % prevented tBHP-induced reactive oxygen species production (evaluated using the H2DCF-DA test in cytofluorometry) in epithelial cells and LPS-induced TNF-α and IL-6 release (evaluated using ELISA technique) in macrophages. A. nodosum extract also increased nuclear SIRT1 activity in epithelial cells. Altogether, these beneficial cellular effects of phlorotannin-rich A. nodosum extract could be used in topical therapeutic formulations against aging.

Does pharmacodynamic interaction of nonenzymatic antioxidants modify response to antioxidant therapy in the process of atherosclerosis?

A discrepancy exists between clinical trials and epidemiological studies on the effect of antioxidants on cardiovascular disease. This discrepancy could be attributed to the lack of knowledge on the effect of interaction of exogenous antioxidant supplementation with one another or on the effect of interaction of exogenously administered antioxidant vitamins with endogenous ones. This study attempts a systematic review of available data on possible synergistic, additive, or antagonistic action of nonenzymatic antioxidants in atherosclerosis. Electronic databases were searched with the available search terms up to and including February 2010. Eligibility criteria were full publications, clinical trials, epidemiological studies, or in vitro or in vivo studies that investigated the effect of pharmacodynamic interaction of 2 or more antioxidants in the process of atherosclerosis and /or the mechanism of interaction. Eligible clinical trials should have at least 4 arms, 1 arm for the study of each antioxidant alone, 1 for the effect of both antioxidants, and 1 arm for the effect of placebo. In vitro data as well as the limited number of identified randomized clinical trials suggested that coadministration of antioxidants results in synergistic or additive interaction in the process of atherosclerosis. No study demonstrated antagonistic interaction between antioxidants.

Importance of extract standardization and in vitro/ex vivo assay selection for the evaluation of antioxidant activity of botanicals: a case study on three Rosmarinus officinalis L. extracts

The overproduction of free radicals and oxygen reactive species is suspected to be implicated in a wide range of metabolic reactions that can have pernicious consequences in the development of a variety of human diseases. Botanical extracts are sources of antioxidants that counteract both free radicals and oxygen reactive species. The processing conditions used in the botanical extraction may influence the antioxidant composition; therefore, different extracts from the same plant may have different antioxidant properties. To illustrate this fact, we conducted a study using three commercial rosemary (Rosmarinus officinalis L.) leaf extracts. The three extracts were standardized to contain, respectively, 20% carnosic acid, 40% ursolic acid, or 20% rosmarinic acid. They were evaluated for their total (hydrophilic + lipophilic) antioxidant effects on oxygen radical absorbance capacity (ORAC), their ferric reducing/antioxidant power (FRAP), and their capacity to inhibit Cu(2+)-induced low-density lipoprotein (LDL) oxidation ex vivo. The ursolic acid extract showed the lowest antioxidant capacity on all models. The rosmarinic acid extract had an antioxidant capacity 1.5 times higher on ORAC and four times higher on FRAP than the carnosic acid extract. However, the carnosic acid extract was better than the rosmarinic acid extract in inhibiting the oxidation of LDL ex vivo. These results encourage conducting further studies to evaluate the carnosic acid and rosmarinic acid extracts in vivo. Our study offers an example of the importance of the extraction procedures, on which depends the nature of the antioxidant composition, and highlights interest to proceed with in vitro/ex vivo assay selection for the evaluation of the antioxidant properties of botanical extracts.

Cardiovascular effects of edible oils: a comparison between four popular edible oils

Edible oils form an essential part of the modern diet. These oils play a role as an energy source, and provide the diet with many beneficial micronutrients. Although a popular conception may be that fat should be avoided, certain edible oils as a dietary supplement may play an important role in the improvement of cardiovascular health. CVD has become one of the leading causes of death worldwide. Dietary supplementation with different oils may have beneficial effects on cardiovascular health. While olive oil and sunflower-seed oil are known to reduce serum cholesterol, fish oil has become well known for reducing potentially fatal cardiac arrhythmias. Recently, red palm oil research has shown beneficial effects on cardiac recovery from ischaemia-reperfusion injury. It is clear that dietary supplementation with edible oils may play a vital role in reducing the mortality rate due to heart disease. The specific benefits and disadvantages of these oils should, however, be explored in greater depth. The present review will attempt to identify the benefits and shortcomings of four popular edible oils, namely olive oil, sunflower-seed oil, fish oil and palm oil. Additionally the present review will aim to reveal potential areas of research which could further enhance our understanding of the effects of edible oils on cardiovascular health.

Determination of toxic perilla ketone, secondary plant metabolites and antioxidative capacity in five Perilla frutescens L. varieties

Perilla frutescens L. is a traditional Asian crop with multiple uses. Several varieties exist but only little data is available about the content of the toxic perilla ketone and secondary plant metabolites of those genotypes. To estimate the nutritional value of this new vegetable more information about those components is necessary. We investigated five genotypes of P. frutescens L. to determine their content of PK, phenolics, carotenoids and AC. AC was examined using ABTS-decolorization assay and lipid peroxidation assay. Carotenoids were identified and quantified by HPLC analysis, phenolics were quantified by means of Folin-Ciocalteu and PK was identified by GC/MS. Two genotypes were found to contain PK, a potent lung toxin, and are therefore not suitable for consumption. The phenolic content and corresponding antioxidative capacity of all genotypes is considerably high compared to other vegetables. All genotypes moreover contain notably high concentrations of carotenoids with contents up to fivefold higher than in other carotenoid rich vegetables. The results indicate that there are several genotypes which are not suitable for consumption due to their content of PK. However PK free genotypes are rich sources of natural antioxidants, and may therefore be considered as a novel vegetable with health promoting properties.

Nutritional benefit of olive oil: the biological effects of hydroxytyrosol and its arylating quinone adducts

Olive oil is the essential component of the Mediterranean diet, a nutritional regimen gaining ever-increasing renown for its beneficial effects on inflammation, cardiovascular disease, and cancer. A unique characteristic of olive oil is its enrichment in oleuropein, a member of the secoiridoid family, which hydrolyzes to the catechol hydroxytyrosol and functions as a hydrophilic phenolic antioxidant that is oxidized to its catechol quinone during redox cycling. Little effort has been spent on exploring the biological properties of the catechol hydroxytyrosol quinone, a strong arylating electrophile that forms Michael adducts with thiol nucleophiles in glutathione and proteins. This study compares the chemical and biological characteristics of hydroxytyrosol with those of the tocopherol family in which Michael adducts of arylating desmethyltocopherol quinones have been identified and correlated with biologic properties including cytotoxicity and induction of endoplasmic reticulum stress. It is noted that hydroxytyrosol and desmethyltocopherols share many similarities, suggesting that Michael adduct formation by an arylating quinone electrophile may contribute to the biological properties of both families, including the unique nutritional benefit of olive oil.

Targeted natural product isolation guided by HPLC-SPE-NMR: constituents of Hubertia species

The hyphenated technique, high-performance liquid chromatography-solid-phase extraction-nuclear magnetic resonance spectroscopy (HPLC-SPE-NMR), has been applied for rapid identification of novel natural products in crude extracts of Hubertia ambavilla and Hubertia tomentosa. The technique allowed full or partial identification of all major extract constituents and demonstrated the presence of unusual quinic acid derivatives containing the (1-hydroxy-4-oxocyclohexa-2,5-dienyl)acetyl residue that exhibit strongly coupled ABXY patterns, the parameters of which were obtained by spin simulations. Using homo- and heteronuclear 2D NMR data acquired in the HPLC-SPE-NMR mode, complete structure determination of three new natural products, i.e., 3,5-di-O-caffeoyl-4-O-[(1-hydroxy-4-oxocyclohexa-2,5-dienyl)acetyl]quinic acid (1), its 2-hydroxy derivative (2), and 3,5-di-O-caffeoyl-4-O-[(4-hydroxyphenyl)acetyl]quinic acid (3), was performed. Finally, targeted isolation of 1 was achieved by SPE fractionation and preparative HPLC, followed by evaluation of its antioxidant and antimicrobial activity. In contrast to chlorogenic acid and 3,5-di-O-caffeoylquinic acid, which act as antioxidants, compound 1 proved at the same conditions to possess prooxidant activity in an assay evaluating the oxidation of human low-density lipoprotein induced by Cu(2+).

Mechanism of the antioxidant to pro-oxidant switch in the behavior of dehydroascorbate during LDL oxidation by copper(II) ions

Oxidised low density lipoprotein (LDL) may be involved in the pathogenesis of atherosclerosis. We have therefore investigated the mechanisms underlying the antioxidant/pro-oxidant behavior of dehydroascorbate, the oxidation product of ascorbic acid, toward LDL incubated with Cu(2+) ions. By monitoring lipid peroxidation through the formation of conjugated dienes and lipid hydroperoxides, we show that the pro-oxidant activity of dehydroascorbate is critically dependent on the presence of lipid hydroperoxides, which accumulate during the early stages of oxidation. Using electron paramagnetic resonance spectroscopy, we show that dehydroascorbate amplifies the generation of alkoxyl radicals during the interaction of copper ions with the model alkyl hydroperoxide, tert-butylhydroperoxide. Under continuous-flow conditions, a prominent doublet signal was detected, which we attribute to both the erythroascorbate and ascorbate free radicals. On this basis, we propose that the pro-oxidant activity of dehydroascorbate toward LDL is due to its known spontaneous interconversion to erythroascorbate and ascorbate, which reduce Cu(2+) to Cu(+) and thereby promote the decomposition of lipid hydroperoxides. Various mechanisms, including copper chelation and Cu(+) oxidation, are suggested to underlie the antioxidant behavior of dehydroascorbate in LDL that is essentially free of lipid hydroperoxides.