Raphael Mechoulam, the Israeli researcher whose work helped to broaden the scientific understanding of cannabis and the compounds that cause the drug’s distinctive high, has died.

Mechoulam, who was 92, died in Jerusalem early this month, according to American Friends of the Hebrew University.

Among Mechoulam’s contributions to the field of marijuana studies was the first isolation of the psychoactive compound of the cannabis plant — tetrahydrocannabinol, or THC. His work earned him the nickname “father of cannabis research.”

He was a “sharp-minded and charismatic pioneer,” said Asher Cohen, the president of the Hebrew University of Jerusalem, where Mechoulam had long served on the faculty.

“Most of the human and scientific knowledge about cannabis was accumulated thanks to Prof. Mechoulam. He paved the way for groundbreaking studies and initiated scientific cooperation between researchers around the world,” said Cohen. “This is a sad day for the academic community and for the university.”

Mechoulam was born in 1930 in Bulgaria. He immigrated to Israel in 1949, and soon pursued an education in chemistry.

When Mechoulam entered the research field in the 1960s, morphine and cocaine had long been isolated from opium and coca, the plants in which the compounds naturally occur, Mechoulam said in a 2018 presentation at the university.

But the same could not be said for marijuana, or hashish, which prevented academic study of the drug in chemistry or pharmacology labs.

So, in 1962, Mechoulam and his research team, then at the Weizmann Institute of Science in Israel, turned their focus to the drug right on the precipice of its explosion in popularity worldwide. (At first, his team acquired the marijuana needed for his research from the local police, he said.)

Over the course of his career, marijuana grew in both popularity and in controversy as debates unfolded over the safety of the drug. In 1970, the U.S. declared marijuana a “controlled substance.”

But Mechoulam, who moved to the Hebrew University of Jerusalem in 1972, continued his studies for decades. He worked to isolate and synthesize other compounds in the drug, as well as to demonstrate the potential for uses in the medical field — including to treat epilepsy and autoimmune diseases.

And his work helped to show that, despite the controversy over its use in the second half of the 20th century, humans have been using cannabis for millennia.

In 1993, he and his team published a study in the journal Nature analyzing the ashes found in the 4th-century Roman tomb of a young woman who had died while giving birth.

“They obviously gave her something to ease the pain or to do something with the hemorrhage she was apparently undergoing. We thought that it might be cannabis,” he told NPR in an interview that year.