2 3 dimethylquinoxaline

D-Glucose, D-fructose, D-maltose, D-lactose, L-lysine, L-serine, L-threonine, L-cysteine, L-norvaline, glyoxal, methylglyoxal, diacetyl, quinoxaline, 2-methylquinoxaline, 2,3-dimethylquinoxaline, o-phenylenediamine dihydrochloride, 1-methylpyrazole, C8-C20 alkane standard, methyl cinnamate, and sodium chloride were purchased from Sigma-Aldrich (St. Louis, MO). Water and ethyl acetate were obtained from J.T. Baker (Philipsburg, NJ, USA). All solutions were stored at 4 °C until analysis. Divinylbenzene/Carboxen/Polydimethylsiloxane (DVB/CAR/PDMS, 50 μm film thickness) solid phase microextraction (SPME) fiber, polypropylene hold caps, and polytetrafluoroethylene (PTFE)/silicone septa were purchased from Supelco Inc. (Belfonte, PA, USA).

Aminoguanidine hydrochloride (AG), bovine serum albumin (BSA), d-fructose, d-ribose, 2,3-dimethylquinoxaline (DQ), gallic acid (GA), resveratrol (RESV), butylated hydroxytoluene (BHT), 2,2-diphenyl-1-picrylhydrazyl (DPPH), methylglyoxal (MGO), 1,2-phenylenediamine (PD), hydrogen peroxide (H₂O₂), trifluoroacetic acid (TFA), lipopolysaccharide (LPS), 2’,7’-dichlorofluorescin diacetate reagent (DCFDA), XAD-16 Amberlite resin, and HPLC-grade methanol were purchased from Sigma-Aldrich Chemical Co. (St. Louis, MO, USA). Beta amyloid 1-42 (Aβ) was purchased from AnaSpec Inc. (Fremont, CA, USA). Griess reagent was purchased from Promega Corp. (Madison, MI, USA).

For all experiments, freshly prepared ultrapure water was taken from Sartorius arium^® pro UV water treatment system (Sartorius AG, Göttingen, Germany). All chemicals were of analytical grade, unless noted otherwise. Acetonitrile, OPD, 2,3-dimethylquinoxaline, MGO, GO, 2-KDG, 3-DG, 5-HMF, D-(+)-glucose monohydrate, methanol and ammonium acetate were purchased from Sigma (Sigma-Aldrich Chemie GmbH, Steinheim, Germany). 3-DGal was obtained from Cayman (Cayman Chemical Company, Ann Arbor, MI, USA). 3,4-DGE was purchased from Carbosynth (Carbosynth Ltd., Compton, Berkshire, UK).
The aqueous phase during LC-MS/MS measurement was a 5 mM ammonium acetate buffer solution adjusted to pH = 3.5 using 0.1% (v/v) acetic acid. It was freshly prepared in accordance to Thomas et al. [54 (link)]. The EZ-Test^® [55 ] Biological Indicator from MesaLabs was used in order to test sterility.

For all experiments, freshly prepared ultrapure water was taken from the Sartorius arium® pro UV water-treatment system (Sartorius AG, Göttingen, Germany). All chemicals were of analytical grade, unless noted otherwise. Acetonitrile, OPD, 2,3-dimethylquinoxaline, MGO, GO, 2-KDG, 3-DG, 5-HMF, D-(+)-glucose, methanol, and ammonium acetate (for mass spectrometry) were purchased from Sigma (Sigma-Aldrich Chemie GmbH, Steinheim, Germany). Acetic acid (glacial) 100%, toluene, sulfuric acid 95–98%, and ethanol 96% were obtained from Merck (Merck KGaA, Darmstadt, Germany). Furthermore, 1,4-dioxane and thymol were purchased from Roth (Carl Roth GmbH & Co. KG, Karlsruhe, Germany). The 3-DGal was obtained from Cayman (Cayman Chemical Company, Ann Arbor, Michigan, USA), and 3,4-DGE was purchased from Carbosynth (Carbosynth Ltd, Compton, Berkshire, UK).
thymol-sulfuric acid reagent was freshly prepared according to the monograph "Glucose" from the Ph. Eur., section C "Thin Layer Chromatography", subitem “Detection” [21 ]:
0.5 g of thymol were solved in a mixture of 5 mL of sulfuric acid and 95 mL of ethanol 96% (v/v). No cooling was required for this step.
The aqueous phase during LC-MS/MS measurement was a 5 mM ammonium acetate buffer solution adjusted to pH = 3.5 using 0.1% (v/v) acetic acid. It was freshly prepared according to Thomas et al (2013) [22 (link)].