15 e 2t isop

Commercially available prostaglandin E 2 (PGE 2 ), F 2 -and E 2 -isoprostanes (IsoPs), 15-F 2t -IsoP and 15-E 2t -IsoP (purity ≥99%) were from Cayman Chemical (Michigan, USA).
Not commercially available F 4 -NeuroPs (20-F 4t -NeuroP, 20-epi-F 4t -NeuroP), F 2 -dihomo-IsoPs (ent-7(R,S)-7-F 2t -dihomo-IsoP, 17-F 2t -dihomo-IsoP) and F 2 -dihomo-IsoF (7(R,S)-ST-Δ 8 -11-dihomo-IsoF) were synthesized at the Institut des Biomolecules Max Mousseron (IBMM) (Montpellier, France) according to procedures reported elsewhere [41] (link)[42] (link)[43] (link)[44] (link).
All the solutions and saliva samples were stored in sterile polypropylene containers from Eppendorf (Milan, Italy).
Phenex™-RC syringe filters (0.2 μm regenerate cellulose, 4 and 15 mm of diameter) were from Phenomenex (California, USA).
The eVol® XCHANGE analytical syringe (20-500 μL) and microextraction by packed sorbent silica-C18 Barrel Insert and Needles (BINs) were purchased from SGE Analytical Science (Melbourne, Australia).
Salivette roll-shaped polyester swabs were purchased from Sarstedt (Nümbrecht, Germany).
A Macherey Nagel Pehanon narrow range (5.2 < pH < 8.1) pH paper strips (Düren, Germany) with a resolution of 0.3 pH units was used to estimate the salivary pH.
An Amicon Ultra-0.5 mL Centrifugal Filters (Darmstadt, Germany) with a cut-off of 3 kDa was used to purify saliva samples.

Isoprostanes' standards of 15(R)-15-F 2t -IsoP, 2,3-dinor-15-epi-15-F 2t -IsoP, 5-F 2t -IsoP, 15-keto-15-E 2t -IsoP, 15-keto-15-F 2t -IsoP, 15-E 2t -IsoP, 15-F 2t -IsoP, the prostaglandins PGE 2 and PGF 2α , as well as the deuterated internal standard (IS) PGF 2α -d 4 were purchased from Cayman Chemical Company (Ann Arbor, Michigan, USA). The standards of 7(RS)-ST-Δ 8 -11-dihomo-IsoF, 10-epi-10-F 4t -NeuroP, d 4 -10epi-10-F 4t -NeuroP, 4(RS)-F 4t -NeuroP, 17-epi-17-F 2t -dihomo-IsoP, 17-F 2t -dihomo-IsoP, 17(RS)-10-epi-SC-Δ 15 -11-dihomo-IsoF, Ent-7(RS)-7-F 2t -dihomo-IsoP, and 14(RS)-14-F 4t -NeuroP were synthetized by Durand's team at the Institute des Biomolécules Max Mousseron (IBMM) (Montpellier, France) (Fig. S1 in Electronic Supplementary material) [34] . Methanol (LC-MS grade) and n-heptane (analytical grade) were obtained from J.T. Baker (Avantor Performance Materials B.V., The Netherlands). Chlorhydric acid and acetic acid glacial (99.5%) were purchased from Panreac (Castellar del Vallés, Barcelona, Spain). Ammonium acetate, sodium acetate, sodium hydroxide, and β-glucuronidase (type H2, from Helix pomatia) were purchased from Sigma-Aldrich (St. Louis, MO, USA). Creatinine assay (MicroVue creatinine EIA) from Quidel Corporation (San Diego, CA, USA).