Kurozu melanoidin, a novel oligoglucan-melanoidin complex from Japanese black vinegar, suppresses adipogenesis in vitro

The black vinegar “kurozu” has an anti-obesity potential, but its active principle is unknown. Here, we isolate and characterize a novel oligoglucan-melanoidin complex, designated kurozu melanoidin (KZM), that suppresses adipogenesis in vitro. KZM was isolated by organic solvent extraction, followed by size-exclusion chromatography. Its average molecular mass was estimated to be 1,090 ± 30 Da using polyethylene glycols as standards. The combination of spectroscopic and chemical analyses revealed the presence of an oligoglucan and a melanoidin structures in KZM. The glucan moiety consisted mainly of 1 → 4 linkage. The MALDI-TOF-MS analysis identified an array of ion peaks that differed in m/z by ~ 162.055 [C6H12O6 − H2O], indicating a variation of glucan chain length. Prominent signals around m/z 500–600 that were unassignable to glucan units suggested ion peaks for the melanoidin moiety. KZM significantly suppressed adipogenesis of 3T3-L1 preadipocytes at 100 μM.