Trans cinnamic acid

Trans-cinnamic acid (≥98.0%) and 4-bromo cinnamic acid were purchased from Acros Organics. 4-amino cinnamic acid and 4-dimethylamino cinnamic acid were purchased from Sigma Aldrich. 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC, ≥98%, Germany) was obtained from Alfa Aesar. 4-(Dimethylamino) pyridine ≥99% was purchased from Sigma-Aldrich. The solvents ethanol (99.5%) and dimethylformamide were purchased from Aga and VWR, respectively. The 7-hydroxy-10-(4″-dimethylamino-cinnamyl)-pyranoflavylium pigment was synthesized according to the procedure described by Chassaing et al.: through the condensation of a 4-methylflavylium salt with 4-dimethylaminobenzaldehyde [14 (link)].

HPLC-grade methanol (MeOH), HPLC-grade acetonitrile (ACN), dimethyl sulfoxide (DMSO), sodium carbonate (Na₂CO₃ > 99%), aluminium chloride (AlCl₃ > 99%), D-(+)-glucose, DL-lactic acid (90%), choline chloride (98%), and standard compounds: ethyl-o-vanillin - ISTD (99%), diosmin (95%), rutin (99%), chrysin (99%), morin hydrate (95%), myricetin ( > 96%), apigenin (97%), (–)-epicatechin (99%), (+)-catechin, vanillic acid (97%), syringic acid (97%), trans-p-coumaric acid (98%), o-coumaric acid (98%), ferulic acid (98%), and rosmarinic acid (97%) were purchased from Sigma-Aldrich (St. Louis, MO, USA). Chlorogenic acid (99%), trans-cinnamic acid (98%), quercetin hydrate (99%) and flavone (99%) were supplied by Acros Organics (Belgium). Protocatehuic acid (99%), caffeic acid (99%) and kaempferol as well as Folin–Ciocalteu phenol reagent (2N), D-(–)-fructose and sodium acetate (CH₃COONa) were supplied by Merck (Germany). Gallic acid (99%) was purchased from Carlo Erba (Italy). Ultrapure water (resistance above 18 MΩ cm) used was obtained from a Milli-Q water purification system.