Pyrroloquinoline quinone (PQQ) is contained in fruits and vegetables and in human breast milk. It has been reported that PQQ has high reactivity and changes to an imidazole structure (imidazole pyrroloquinoline) by a reaction with an amino acid at a high ratio in nature. A comparative study was conducted to clarify physiological effects including neuroprotective effects, growth-promoting effect, antioxidative effects and a stimulatory effect on mitochondriogensis of PQQ and imidazole pyrroloquinoline (IPQ) using a human neuroblastoma cell line and a hepatocellular carcinoma cell line. We also compared the expression levels of human cytochrome c oxidase subunit IV isoform I (COX4/1), which is an index of the amount of mitochondria in the cells that had been exposed to PQQ, PQQH 2 and IPQ. The results of the comparison showed that IPQ had almost the same biological activities as those of PQQ except for anti-oxidative activity. It was also shown that PQQ and IPQ improve the memory learning ability of aged mice and that BioPQQ® improves brain function in the language field in humans.

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