Liverwort plants contain a painkiller similar to the one in marijuana

A chemical compound found in liverworts may provide the pain and inflammation relief of pot’s THC but without the same kind of high.

Both the molecule, called perrottetinene, and tetrahydrocannabinol, or THC — the mind-altering substance found in marijuana — have similar molecular structures. Lab tests with human brain cells and in mice have revealed that, like THC, perrottetinene easily attaches to the brain’s cannabinoid receptors, or molecular docking stations, dampening the effects of pain signals, researchers report October 24 in Science Advances.

“Nobody really notices [liverworts] because they’re so small,” says Douglas Kinghorn, a phytochemist at Ohio State University in Columbus. “Sometimes you find important medicinal compounds in plants from unexpected sources.”

A group of Japanese scientists in 1994 discovered perrottetinene in liverworts, but the new study is the strongest evidence yet that the compound is a psychoactive cannabinoid. Previously, cannabis was the only plant known to produce such cannabinoids.  

So far, only three species of liverwort in the Radula genus — found in Japan, Costa Rica, New Zealand and Tasmania— are known to produce the compound. Because the plants make so little of the substance, researchers have struggled to study its effects, until now.

The researchers created synthetic versions of perrottetinene and tested them on mice. The team tracked the animals’ pain response, body temperature and movement — measures of the compound’s psychoactivity. The results suggested that perrottetinene may be slightly less psychoactive than THC, says study coauthor Jürg Gertsch, a biochemist at the University of Bern in Switzerland. The liverwort compound may also have fewer negative side effects such as memory loss and loss of coordination, he says.

“Cannabinoids have a broad range of applications,” Gertsch notes. Eventually, the team hopes that pharmaceutical companies will manufacture the substance as a potential alternative to marijuana which, though prescribed to alleviate certain ailments and legalized in some states, remains classified as an illegal narcotic under U.S. federal law.

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Editor’s note: This story was updated November 7, 2018, to correct that the study did not map the molecular structure of perrottetinene.