Formation of Maillard Reaction Products in Aged Sorghum Vinegar during Ageing and Protective Effects of Pure Vinegar Melanoidin Against CCl4-Induced Rat Hepatic Damage

Research background. The processing method generally affects the toxicity and bio-logical activity of aged sorghum vinegar. This study investigates the changes in the inter-mediate Maillard reaction products of sorghum vinegar during ageing and the in vivo hepatoprotective effects of pure melanoidin obtained from it. Experimental approach. High-performance liquid chromatography (HPLC) and fluores-cence spectrophotometry were utilized to quantify intermediate Maillard reaction prod-ucts. The CCl4-induced liver damage in rats was used to evaluate the protective role of pure melanoidin in rat liver.Results and conclusions. Compared with the initial concentration, the 18-month ageing process caused a 1.2-to 3.3-fold increase in the concentrations of intermediate Maillard reaction products, i.e. 5-hydroxymethylfurfural (HMF), 5-methylfurfural (MF), methygly-oxal (MGO), glyoxal (GO) and advanced glycation end products (AGEs). The concentrations of HMF in the aged sorghum vinegar were 6.1-fold higher than the 450 mu M limit standard for honey, implying the need for shortening the ageing of the vinegar in practice for safe-ty concerns. Pure melanoidin (Mr>3.5 kDa) demonstrated significant protective effects against CCl4-induced rat liver damage, as evidenced by normalized serum biochemical parameters (transaminases and total bilirubin), suppressing hepatic lipid peroxidation and reactive oxygen species, as well as increasing glutathione amount and restoring antioxi-dant enzyme activities. Histopathological analysis revealed that melanoidin in vinegar reduced cell infiltration and vacuolar hepatocyte necrosis in rat liver. The findings demon-strated that a shortened ageing process should be considered in practice to ensure the safety of aged sorghum vinegar. Vinegar melanoidin is a potential alternative for the pre-vention of hepatic oxidative damage.Novelty and scientific contribution. This study demonstrates that the manufacturing process had a profound influence on the generation of vinegar intermediate Maillard re-action products. In particular, it revealed the in vivo hepatoprotective effect of pure mel-anoidin from aged sorghum vinegar, and provides insight into the in vivo biological activ-ity of melanoidin.