"They absolutely should not be used as recreational drugs," he said.
Professor Huffman, an organic chemist at Clemson University, said the compounds appearing in "fake marijuana" were among many created by his group during research supported by the National Institute on Drug Abuse between 1984 and 2010, aiming to understand the relationship between the chemical structure and the biological activity of cannabinoids.
Cannabinoids include THC - the active ingredient in cannabis - but also other substances that interact with the cannabinoid receptors in the brain and other organs, he said.
"These receptors don't exist so that people can smoke marijuana and get high; they play a role in regulating appetite, nausea, mood, pain and inflammation."