A California bill that would have imposed regulations on kratom products was quietly shelved Thursday following a clash between advocacy groups focused on the burgeoning industry.

Kratom products are derived from the leaves of a tree that grows in Southeast Asia, where kratom has long been chewed and brewed into teas. As it has gained more popularity around the globe, greenish capsules, powders and extracts have popped up in vape and smoke shops in California.

Scientists are still learning about its complex effects, which can range from stimulant to sedative and stem from chemical compounds called alkaloids. The Food and Drug Administration has warned against using kratom for medical treatment and says it is “not appropriate for use as a dietary supplement.” Among the reported side effects have been seizures, vomiting and heart problems. Kratom has also been involved in a small share of overdose deaths, although most also involved other drugs, analyses have found.

A bill proposed by Assemblymember Matt Haney (D-San Francisco) would have required kratom products to be registered with the state, and to carry mandated labeling and warnings. It also would have prohibited sales to anyone under 21.

In addition, Assembly Bill 2365 would have banned products containing synthesized versions of kratom alkaloids. And it would have prohibited ones in which a specific chemical makes up more than 1% of its alkaloid content.

That chemical is 7-hydroxymitragynine, also known as 7-OH. It is typically found in the dried kratom leaf in very low concentrations, although a more common alkaloid in the plant — mitragynine — breaks down in the human body to create 7-OH as well.

Scientists have raised concerns about its effects: One study in the Journal of Medical Toxicology said 7-OH “is likely to be a major contributing factor to the addictive potential of kratom.” Another article published in Addiction Biology said 7-OH “should be considered a kratom constituent with high abuse potential.”

Kirsten Smith, an assistant professor in the Department of Psychiatry and Behavioral Sciences at Johns Hopkins University, said that because 7-OH appears naturally at very low levels in the kratom leaf, products with much higher levels of 7-OH are “easily identifiable as being manipulated and man-made.”

“It’s no longer the botanical as it’s been used in nature,” Smith said, adding that she didn’t consider synthesized 7-OH products to be kratom at all.

Kratom advocacy groups were split over the California bill. It was backed by the Global Kratom Coalition, whose executive director, Matthew Lowe, argued kratom products should have an alkaloid content similar to the natural plant that has long been used. The coalition was joined by law enforcement groups in backing AB 2365.

In the opposing camp were the American Kratom Assn., which has fought bans on kratom products throughout the country and backed other state regulations, and Holistic Alternative Recovery Trust, which wants 7-OH to be explored as an alternative to opioids for pain relief.

The American Kratom Assn. contended that the regulatory structure needed for the California bill would be so costly that few companies would be able to pay the needed fees. State officials estimated it could cost over $4 million annually to regulate kratom under the bill.

AB 2365 “is promoted by one company who will benefit from the onerous provisions … to the detriment of small and mid-sized kratom manufacturers,” said Mac Haddow, its senior fellow on public policy. He argued Botanic Tonics — a beverage company listed as a supporter of the Global Kratom Coalition — had enough market presence that for them, the registration fees would not be prohibitive.

The Holistic Alternative Recovery Trust argued for a higher limit on 7-OH, saying that California should avoid being so restrictive that the products would lose therapeutic benefits.

Lowe said that the level they were pushing for — 2% of dry weight rather than 1% of the alkaloid content — was vastly higher and would threaten consumer safety. As for concerns about fees, Lowe said the focus should be “how the provisions in the bill inform and protect consumers, rather than the cost on the industry.”

“The Global Kratom Coalition is not looking to support any single vendor. We’re looking to ensure that kratom products are safe,” Lowe said. He added that the bill envisioned a tiered system for fees related to annual sales in California, which would allow lower fees for smaller companies.

AB 2365 stalled in the state Senate’s appropriations committee as lawmakers culled hundreds of bills on the so-called suspense file. The process allows legislative leaders to quietly halt bills that would have significant costs or pose challenging political dynamics, averting the need for many lawmakers to have to weigh in.

Haney said that “Californians are not safer by leaving kratom entirely unregulated in our state,” calling it “a total free-for-all.” The lawmaker said he plans to reach out to the California Department of Public Health to weigh next steps and hopes the FDA will take action, rather than leaving the matter to states.

“I have no interest in benefiting any particular player” in the kratom industry, but chose to err on the side of less potency, to the chagrin of “people who want to sell much stronger versions of kratom,” Haney said. He said if discussions continue, he would like the Department of Public Health to help define what is “synthetic.”

The public health department, which would have handled product registration under the bill, said it has not conducted any scientific assessment of the safety risks of 7-OH in kratom products.

The Global Kratom Coalition spent $15,000 on lobbying related to the bill, according to financial disclosures available as of Thursday. It also contributed $5,500 in political donations to Haney, who introduced AB 2365, and $36,400 to Atty. Gen. Rob Bonta, who supported it, according to state records.

Botanic Tonics, in turn, reported spending $90,000 on lobbying during this legislative session, including $30,000 during a period it was advocating on AB 2365. The company said other expenses were for “advice and counsel on the regulatory and legislative landscape specific to California.”

Holistic Alternative Recovery Trust reported spending $18,000 on lobbying over AB 2365. The American Kratom Assn. said it had not hired a lobbyist until the end of July and would report its spending after that point.

And the bill also drew interest from the kratom company MIT45 Inc., which reported spending $60,000 on lobbying. A company leader did not immediately clarify its position on the bill.

The National Institute on Drug Abuse says that “much is still unknown about chemical compounds related to kratom,” its health impacts and possible therapeutic uses, complicating discussions among regulators in California and across the country.

The Global Kratom Coalition has funded research on kratom at the University of Florida college of pharmacy, where researcher Christopher McCurdy and others have raised concerns about “semi-synthetic, isolated” alkaloids. Lowe said his group provided $500,000 total this year. Advancing research on kratom is part of its mission and “ensures that regulations are led by the evolving science,” he said.

McCurdy said the coalition and “many independent kratom vendors” had helped fund research there, but “no one that donates has any influence on what studies we conduct” and “they all understand that we will publish our findings without their review or consent.”

Smith said she had done consulting for the Global Kratom Coalition in the past, but that her research was funded by NIDA, not the coalition or any other groups connected to the kratom industry.

“We are in such early, early days of research” on kratom, she said.