Total phenolic compounds in milk from different species. Design of an extraction technique for quantification using the Folin-Ciocalteu method.

Milk protects the health of newborns because it contains essential compounds that perform metabolic activities. Despite these benefits, the study of phenolic compounds in milk has been poorly explored. The objective of this study was to develop and validate a technique for extracting total phenolic compounds (TPCs) from a milk matrix and then analyzing them using the Folin-Ciocalteu method. The extraction technique was applied to goat milk and involved the addition of methanol, acetonitrile, and Carrez I and II reagents, after which protein was separated from fat through centrifugation. Subsequently, the technique was applied to goat (69.03±6.23mg GAE/L), cow (49.00±10.77mg GAE/L), sheep (167.6±58.77mg GAE/L) and human milk (82.45±12.3mg GAE/L). The technique showed an acceptable linearity (R(2)=0.9998), limit of detection (6.03mg GAE/L) and quantification (16.2mg GAE/L), repeatability (RSD=4%), reproducibility (RSD=6.8%) and recovery (>85.41%); it is thus effective and can be used in the routine analysis of milk. TPCs obtained from each type of milk indicate a high variability among species and among members of the same species.

The effect of olive oil polyphenols on antibodies against oxidized LDL. A randomized clinical trial.

BACKGROUND & AIM: Oxidized LDL (oxLDL) is a highly immunogenic particle that plays a key role in the development of atherosclerosis. Some data suggest a protective role of OxLDL autoantibodies (OLAB) in atherosclerosis. Our aim was to assess the effect of olive oil polyphenols on the immunogenicity of oxLDL to autoantibody generation. METHODS: In a crossover, controlled trial, 200 healthy men were randomly assigned to 3-week sequences of 25 mL/day of 3 olive oils with high (366 mg/kg), medium (164 mg/kg), and low (2.7 mg/kg) phenolic content. RESULTS: Plasma OLAB concentration was inversely associated with oxLDL (p < 0.001). Olive oil phenolic content increased OLAB generation, with the effect being stronger at higher concentrations of oxLDL (p = 0.020 for interaction). A direct relationship was observed between OLAB and the total olive oil phenol content in LDL (r = 0.209; p = 0.014). OLAB concentrations, adjusted for oxLDL, increased directly in a dose-dependent manner with the polyphenol content of the olive oil administered (p = 0.023). CONCLUSION: Olive oil polyphenols promote OLAB generation. This effect is stronger at higher concentrations of lipid oxidative damage.

Elevated circulating LDL phenol levels in men who consumed virgin rather than refined olive oil are associated with less oxidation of plasma LDL.

In human LDL, the bioactivity of olive oil phenols is determined by the in vivo disposition of the biological metabolites of these compounds. Here, we examined how the ingestion of 2 similar olive oils affected the content of the metabolic forms of olive oil phenols in LDL in men. The oils differed in phenol concentrations as follows: high (629 mg/L) for virgin olive oil (VOO) and null (0 mg/L) for refined olive oil (ROO). The study population consisted of a subsample from the EUROLIVE study and a randomized controlled, crossover design was used. Intervention periods lasted 3 wk and were preceded by a 2-wk washout period. The levels of LDL hydroxytyrosol monosulfate and homovanillic acid sulfate, but not of tyrosol sulfate, increased after VOO ingestion (P < 0.05), whereas the concentrations of circulating oxidation markers, including oxidized LDL (oxLDL), conjugated dienes, and hydroxy fatty acids, decreased (P < 0.05). The levels of LDL phenols and oxidation markers were not affected by ROO consumption. The relative increase in the 3 LDL phenols was greater when men consumed VOO than when they consumed ROO (P < 0.05), as was the relative decrease in plasma oxLDL (P = 0.001) and hydroxy fatty acids (P < 0.001). Plasma oxLDL concentrations were negatively correlated with the LDL phenol levels (r = -0.296; P = 0.013). Phenols in LDL were not associated with other oxidation markers. In summary, the phenol concentration of olive oil modulates the phenolic metabolite content in LDL after sustained, daily consumption. The inverse relationship of these metabolites with the degree of LDL oxidation supports the in vivo antioxidant role of olive oil phenolics compounds.

Changes in the phenolic content of low density lipoprotein after olive oil consumption in men. A randomized crossover controlled trial.

Olive oil decreases the risk of CVD. This effect may be due to the fatty acid profile of the oil, but it may also be due to its antioxidant content which differs depending on the type of olive oil. In this study, the concentrations of oleic acid and antioxidants (phenolic compounds and vitamin E) in plasma and LDL were compared after consumption of three similar olive oils, but with differences in their phenolic content. Thirty healthy volunteers participated in a placebo-controlled, double-blind, crossover, randomized supplementation trial. Virgin, common, and refined olive oils were administered during three periods of 3 weeks separated by a 2-week washout period. Participants were requested to ingest a daily dose of 25 ml raw olive oil, distributed over the three meals of the day, during intervention periods. All three olive oils caused an increase in plasma and LDL oleic acid (P < 0.05) content. Olive oils rich in phenolic compounds led to an increase in phenolic compounds in LDL (P < 0.005). The concentration of phenolic compounds in LDL was directly correlated with the phenolic concentration in the olive oils. The increase in the phenolic content of LDL could account for the increase of the resistance of LDL to oxidation, and the decrease of the in vivo oxidized LDL, observed in the frame of this trial. Our results support the hypothesis that a daily intake of virgin olive oil promotes protective LDL changes ahead of its oxidation.

Presence of virgin olive oil phenolic metabolites in human low density lipoprotein fraction: determination by high-performance liquid chromatography-electrospray ionization tandem mass spectrometry.

The biological benefits of olive oil in preventing the oxidation of low density lipoprotein (LDL) would seem to be linked to its high monounsaturated fatty acid contents, but also to its respective phenolic compounds contents. One prerequisite to assess the in vivo physiological significance of phenolic compounds is to determine their presence in human LDL following the ingestion of virgin olive oil. In this work, olive oil phenolic metabolites were identified using high-performance liquid chromatography in tandem with electrospray mass spectrometry (HPLC-ESI-MS/MS) detection, after solid phase extraction (SPE). Quantitative methods were developed in carrying out linearity, precision, sensitivity and recovery tests. The results from two methods of LDL separation were compared and shorter LDL isolation procedure showed a better recovery for antioxidants compounds in LDL. The metabolites identified in LDL were: hydroxytyrosol monoglucuronide, hydroxytyrosol monosulfate, tyrosol glucuronide, tyrosol sulfate and homovanillic acid sulfate. The fact that olive oil phenolic metabolites are able to bind LDL strengthens claims that these compounds act as in vivo antioxidants.

Rapid high-performance liquid chromatography-electrospray ionization tandem mass spectrometry method for qualitative and quantitative analysis of virgin olive oil phenolic metabolites in human low-density lipoproteins.

A rapid method for detection and quantification of metabolites of specific olive oil phenolic compounds (hydroxytyrosol monoglucuronide, hydroxytyrosol monosulfate, tyrosol glucuronide, tyrosol sulfate and homovanillic acid sulfate) in low-density lipoprotein (LDL) fractions by solid-phase extraction (SPE) and high-performance liquid chromatography coupled to electrospray ionization tandem mass spectrometry (HPLC/ESI-MS/MS) is described. A 3 microm particle size fast C18 Luna column, 5 cm x 2.0 mm I.D., was used at a flow rate of 0.6 mL/min with a mobile phase consisting of 0.1% (v/v) formic acid (A) and acetonitrile (B). A linear gradient profile was used for separation at column temperature 40 degrees C. The proposed chromatographic procedure is rapid without loosing its separation efficiency and sensitivity. Validation proofs were carried out for the method described, showing a linear system (r>0.99) and a recovery of 81.9 and 101.3% for hydroxytyrosol and homovanillic acid, respectively. The results show that this method is effective and can be used in routine analysis.

Characterization and quantification of phenolic compounds in olive oils by solid-phase extraction, HPLC-DAD, and HPLC-MS/MS.

A simple and reproducible method for qualitative and quantitative analysis of phenolic compounds in virgin olive oils by solid-phase extraction (SPE), high performance liquid chromatography with diode array detector (HPLC-DAD), and HPLC-mass spectrometry (MS) in tandem mode was developed. The polar fraction was obtained from samples of three different virgin olive oils. Detection and quantification were performed at 280, 240, and 320 nm. For identification purposes, HPLC-MS/MS was equipped with turbo ion spray source in the negative-ion mode. Twenty compounds of twenty-three detected and quantified were characterized. The method showed satisfactory linearity (r > 0.99), good recovery, satisfactory precision, and appropriate limits of detection (LOD) and quantification (LOQ).