Formation of pyrroles, 2-pyrrolidones, and pyridones by heating of 4-aminobutyric acid and reducing sugars

Activity-Guided Identification of in Vitro Antioxidants in Beer

“…After separation from solvent in vacuum, the subfractions and purified compounds were freeze-dried and then analyzed by LC-TOF-MS, LC-MS/MS, and 1D/2D-NMR spectroscopy as well as ORAC-, HPS-, and LA-assays, respectively. In accordance with the spectroscopic data (UV/vis, LC-TOF-MS, 1 H/ 13 C NMR), the structures of the previously reported 4-[2-formyl-5-(hydroxymethyl)­pyrrol-1-yl]­butyric acid ( 28 ) and hordatine A ( 29 ) were confirmed. The chemical structures of hordatine B ( 30 ) and hordatine C ( 31 ) have been determined by means of UV/vis, LC-TOF-MS, and 1D/2D-NMR experiments, and, to the best of our knowledge, no detailed NMR data have been reported earlier.…”

“…Monitoring the effluent at λ = 280 nm, 20 subfractions were collected, namely IIA-9-1 to IIA-9-20, solvent separated in vacuum, and lyophilized for 48 h, and their antioxidant activity was analyzed by means of the ORAC-, HPS-, and LA-assays, respectively. After rechromatography, comparison of spectroscopic data (UV/vis, LC-TOF-MS, 1 H/ 13 C NMR) with literature data revealed saponarin ( 26 ) and 4-(2-formylpyrrol-1-yl)­butyric acid ( 27 ) as the key antioxidants.…”

“…In comparison to 27 , the 1 H NMR spectrum of compound 28 showed an additional signal of a hydroxymethyl group (H 2 –C­(6)) at 4.64 ppm, while the pyrrole proton at C(5) was lacking. Although isolated earlier as a Maillard reaction product from carbohydrate/aminobutyric acid model reactions, , 4-[2-formyl-5-(hydroxymethyl)­pyrrol-1-yl]­butyric acid ( 28 ), isolated from fraction IIA-8-10, has not been previously reported as a constituent of beer (Figure ).…”

Maillard Reaction of Free and Nucleic Acid-Bound 2-Deoxy-d-ribose and d-Ribose with ω-Amino Acids

“…Thus, we investigated the reaction between ω-amino acids and nucleic acid-bound sugars, under both stringent (160 °C) and mild (40 °C) conditions. Continuing our previous work on Maillard reaction pathways (Tressl et al, 1993a(Tressl et al, ,b, 1994 we characterized the products of model compounds of peptide-bound lysine (6-aminocaproic acid, 4-aminobutyric acid) reacting with D-ribose, 2-deoxy-D-ribose, RNA, and DNA, respectively. For comparison, incubations of the nucleic acids without addition of ω-amino acids were studied.…”

6-(2-Formyl-5-methyl-1H-pyrrol-1-yl)hexanoic Acid as a Novel Retronasal Burnt Aroma Compound in Soy Sauce Aroma-Type Chinese Baijiu

“…This is the first time that compound 1 has been identified in Baijiu with retronasal burnt aroma activity. Because a structural analogue of compound 1, 4-(2-formyl-5-methyl-l-pyrrol-1-yl)butanoic acid, has been discovered as one of the Maillard reaction products of L-rhamnose and 4-aminobutyric 34 and the repeated "high-temperature" manufacturing of soy sauce Baijiu provides a favorable condition for the Maillard reaction, compound 1 is thus suggested to be generated in the Maillard reaction during soy sauce Baijiu manufacturing. Soy sauce Baijiu has various "N"-containing heterocycle compounds, such as pyrazines 35 and pyrrols, 36 whereas knowledge about the aroma impacts of these compounds is scarce.…”