A plant used for centuries as a pain reliever in Chinese medicine may help fight chronic pain, U.S. and Chinese researchers said Thursday.

The flowering plant Corydalis, a member of the poppy family, contains a key pain-relieving ingredient known as dehydrocorybulbine (DHCB) in their roots, the researchers wrote in the U.S. journal Current Biology.

"Our study reports the discovery of a new natural product that can relieve pain," Olivier Civelli of the University of California, Irvine, said in a statement.

"This analgesic acts in animal assays against the three types of pain that afflict humans, including acute, inflammatory, and neuropathic or chronic pain."

Civelli, along with Xinmiao Liang of Chinese Academy of Sciences, made the discovery as part of the "herbalome" project which aims to catalogue all of the chemical components of traditional Chinese medicine.

The Corydalis plants grow mainly in central eastern China, where underground tubers are harvested, ground, and boiled in hot vinegar. Those concoctions are often prescribed to treat pain, including headaches and back pain.

The researchers found that Corydalis appeared to act in a manner similar to morphine. "We landed on DHCB but rapidly found that it acts not through the morphine receptor but through other receptors, in particular one that binds dopamine," Civelli said.

While Corydalis extracts or isolated DHCB work against all types of pain, they hold special promise for those who suffer with persistent, low-level chronic pain, the researchers said.

Unlike traditional opiate drugs such as morphine, DHCB doesn't appear to lose effectiveness over time.

"We have good pain medications for acute pain: codeine or morphine, for example," Civelli said. "We have pain medication for inflammatory pain, such as aspirin or acetaminophen. We do not have good medications for chronic pain. DHCB may not be able to relieve strong chronic pain, but may be used for low-level chronic pain."

Although Corydalis preparations of various types can already be purchased on-line, the researchers said that further testing for DHCB's toxicity is needed before doctors should consider prescribing it to patients.