Research background. The processing method generally affects the toxicity and biological activity of aged sorghum vinegar (ASV). This study investigated the changes in the intermediate Maillard reaction products (MRPs) of ASV during the aging process and the in vivo hepatoprotective effects of pure ASV melanoidin. Experimental approach. High-performance liquid chromatography (HPLC) and fluorescence spectrophotometry were utilized to quantify intermediate MRPs. The CCl4-induced rat model of liver damage was used to evaluate the protective role of pure melanoidin in rat liver. Results and conclusions. Compared with the initial concentration, the 18-month aging process caused a 1.2- to 3.3-fold increase in the levels of intermediate MRPs, i.e. 5-hydroxymethylfurfural (HMF), 5-methylfurfural (MF), methyglyoxal (MGO), glyoxal (GO) and advanced glycation end products (AGEs). The levels of HMF in ASV were 6.1-fold higher than the 450 μM limit standard for honey, implying the need for shortening the aging of ASV in practice for safety concern. 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 level and restoring antioxidant enzyme activities. Histopathological analysis revealed that melanoidin in vinegar reduced cell infiltration and vacuolar hepatocyte necrosis in rat liver. The findings demonstrated that a shortened aging process should be considered in practice to ensure the safety of ASV. Vinegar melanoidin is a potential alternative for the prevention of hepatic oxidative damage. Novelty and scientific contribution. This study demonstrated that the manufacturing process had a profound influence on the generation of vinegar intermediate MRPs. In particular, it revealed the in vivo hepatoprotective effect of pure ASV melanoidin, and provides insight into the in vivo biological activity of melanoidin.

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