Erinacines A, B and C, strong stimulators of nerve growth factor (NGF)-synthesis, from the mycelia of Hericium erinaceum

Pyrroloquinoline quinone (PQQ), which is a cofactor of microbial quinoprotein enzymes, was found to be a potent enhancer of nerve growth factor (NGF) production in vitro. One of PQQ derivatives, oxazopyrroloquinoline trimethylester, had little activity in vitro, but increased the NGF content in rat brain in vivo.