Suppression of blood lipid concentrations by volatile Maillard reaction products.
OBJECTIVE
Although the chemistry of Maillard reaction products (MRPs) in foods has been well studied, few reports on the nutritional characteristics of MRPs in experimental animals and humans have been found. In this study, our interest was focused on the volatile MRPs (vMRPs) found in heated foods.


METHODS
To confirm the metabolic oxidations of six methylpyrazines and pyrrole-2-carboxaldehyde to carboxylic acid derivatives in vivo, we administrated these compounds orally to Wistar rats with a single dose of 50 mg/kg. Urine samples were collected over 24 h, followed by determination using high-performance liquid chromatographic procedures. Eight pyrazinoic acids, 2-furoic acid, and 5-hydroxymethyl-2-furoic acid were administered orally to rats with a single dose of 100 or 300 mg/kg, and blood non-esterified fatty acid and triacylglycerol concentrations were analyzed.


RESULTS
Monomethylpyrazine, 2,3-, 2,5-, and 2,6-dimethylpyrazine, trimethylpyrazine, and tetramethylpyrazine were metabolized to a corresponding pyrazinoic acid such as non-substituted pyrazinioic acid, 3-, 5-, or 6-methylpyrazinoic acid, 3,5-, 3,6-, and 5,6-dimethylpyrazinoic acid, and trimethylpyrazinoic acid, in appropriate yields, respectively. Further, pyrrole-2-carboxaldehyde was metabolized to pyrrole-2-carboxylic acid. Non-substituted and 5-methylpyrazinoic acid and 2-furoic and 5-hydroxymethyl-2-furoic acid showed significant non-esterified fatty acid-lowering effects. 5-Methyl and 6-methylpyrazinoic acid and 2-furoic acid showed significant triacylglycerol-lowering effects. Pyrazinoic acids with methyl substitution at position 3 showed no lipid-lowering effect.


CONCLUSIONS
These results suggest that the vMRPs such as methylpyrazines are metabolized to their corresponding pyrazinoic acids. These vMRPs and their metabolites exhibit blood lipid-lowering effects in rats.
Kagami
Keisuke
K
Department of Clinical Pharmacology, Tokyo University of Pharmacy and Life Sciences, Tokyo, Japan. y991059@educ.ps.toyaku.ac.jp
Onda
Kenji
K
Oka
Kitaro
K
Hirano
Toshihiko
T
D000818:Animals; D002851:Chromatography, High Pressure Liquid; D005230:Fatty Acids, Nonesterified / Q000097:blood*; D000960:Hypolipidemic Agents / Q000008:administration & dosage*; D015416:Maillard Reaction; D008297:Male; D010084:Oxidation-Reduction; D011718:Pyrazinamide / Q000031:analogs & derivatives / Q000378:metabolism; D011719:Pyrazines / Q000008:administration & dosage*; D011758:Pyrroles / Q000008:administration & dosage*; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D016896:Treatment Outcome; D014280:Triglycerides / Q000097:blood*; D016482:Urinalysis; D014835:Volatilization
D005230:Fatty Acids, Nonesterified; D000960:Hypolipidemic Agents; D011719:Pyrazines; D011758:Pyrroles; D014280:Triglycerides; C051266:pyrrole-2-carboxaldehyde; D011718:Pyrazinamide; C005296:pyrazinoic acid