Studies on insulin-like substances in Korean red ginseng.
Korean red ginseng powder was found to contain adenosine and an acidic substance which inhibited epinephrine-induced lipolysis and stimulated insulin-mediated lipogenesis from glucose (3, 4). In the present experiment, the chemical structure of this acidic substance is determined to be pyro-glutamic acid. Pyroglutamic acid exhibits selective modulations toward the opposite metabolic pathways in rat adipocytes; it inhibits the lipolysis but rather stimulates the lipogenesis. Based on these results, we suggest to call these substances (adenosine and pyro-glutamic acid) "selective modulators".