Acid-Induced Structural Modifications of Unsaturated Fatty Acids and Phenolic Olive Oil Constituents by Nitrite Ions:  A Chemical Assessment

Abstract

The structural modifications of the unsaturated fatty acid components of triglycerides in extra virgin olive oil (EVOO) following exposure to nitrite ions in acidic media were determined by two-dimensional (2D) NMR spectroscopy, aided by (15)N labeling and GC analysis, allowing investigation of the matrix without fractionation steps. In the presence of excess nitrite ions in a 1% sulfuric acid/oil biphasic system, extensive double bond isomerization of the oleic/linoleic acid components of triglycerides was observed associated with nitration/oxidation processes. Structurally modified species were identified as E/Z-nitroalkene, 1,2-nitrohydroxy, and 3-nitro-1-alkene(1,5-diene) derivatives based on (1)H, (13)C, and (15)N 2D NMR analysis in comparison with model compounds. Minor constituents of EVOO, including phenolic compounds and tocopherols, were also substantially modified by nitrite-derived nitrating species, even under milder reaction conditions relevant to those occurring in the gastric compartments. Novel nitrated derivatives of tyrosol, hydroxytyrosol, and oleuropein (6-8) were identified by LC/MS analysis of the polar fraction of EVOO and by comparison with synthetic samples. Overall, these results provide the first systematic description at the chemical level of the consequences of exposing EVOO to nitrite ions at acidic pH and offer an improved basis for further investigations in the field of toxic nitrosation/nitration reactions and dietary antinitrosating agents.

Plant Catechols and Their S-Glutathionyl Conjugates as Antinitrosating Agents: Expedient Synthesis and Remarkable Potency of 5-S-Glutathionylpiceatannol

“…All attempts at isolating reaction products from 7b were unsuccessful, due to their fast degradation to very polar and ill-defined materials eluding chromatography. Detectable amounts of ring nitration products were formed from 2 (14,16) and 4 (21), whereas 1 gave as a main product a previously reported hydroxyoxime (16), as determined by HPLC analysis in comparison with authentic standards. Data in Figure 6 indicated that 2 was the most effective inhibitor of nitrotyrosine formation (>95% inhibition at 100 1, 4, and 3, in that order.…”

Protection from hypertension in mice by the Mediterranean diet is mediated by nitro fatty acid inhibition of soluble epoxide hydrolase

“…NO 2 -OA was selected for further study because of its endogenous presence, structural simplicity, and well-understood pharmacokinetics and metabolism (19,20). Furthermore, NO 2 -OA and other free and esterified fatty acid nitroalkenes are formed at elevated levels when unsaturated fatty acids are ingested together with a source of nitrite (26). Given the Mediterranean diet is high in both unsaturated fatty acids, for example from olive oil, as well as nitrite from vegetables, nitro fatty acid formation leading to sEH inhibition may contribute to BP-lowering and disease prevention provided by these dietary constituents.…”

“…Of relevance, the Mediterranean diet is characterized by high consumption of unsaturated fatty acids, especially from olive oil and fish rich in oleic and linoleic acid, together with vegetables rich in nitrite and nitrate (25). The acidic and low-oxygen conditions in the stomach provide an environment for efficient nitration of such unsaturated fatty acids by nitrite (26). NO 2 -OA normalizes blood pressure in an angiotensin (Ang) II-induced murine model of hypertension via undefined mechanisms (27).…”

Powering tyrosol antioxidant capacity and osteogenic activity by biocatalytic polymerization

“…46 Most of the benecial properties of tyrosol have been ascribed to its potent antioxidant and scavenging properties against ROS and reactive nitrogen species generated in settings of oxidative stress. 43,47,48 In this paper we report the rst preparation and characterization of a polymer of tyrosol, OligoTyrosol (OligoTyr), via a convenient HRP/H 2 O 2 -catalyzed oxidation process, and disclose the potential of OligoTyr incorporated into a PLAscaffold for use in bone tissue engineering. Specic aims of this study include: (a) preparation, structural characterization and evaluation of the antioxidant and osteogenic properties of OligoTyr; (b) preparation and characterization of a PLA-OligoTyr composite scaffold at high porosity; (c) evaluation of OligoTyr release kinetics from PLA-OligoTyr scaffold in vitro.…”