Millions of Americans take St. John’s wort in herbal supplement form for a variety of mild health conditions. Now, researchers at the University of Southern California, Los Angeles’ Keck School of Medicine are saying that a synthetic form of a compound found in the plant may be used to supplement brain tumor therapies.

A study published in the journal Cancer stated that an man-made version of hypericin, which naturally occurs in St. John’s wort, appears to inhibit the growth of some malignant brain tumors.

In particular, researchers found that a regimen of synthetic hypericin was able to stabilize or partially slow the growth of cerebral gliomas in half of the participants given the drug for 60 days.

The team estimated that 10,000 cerebral gliomas are diagnosed every year in the U.S. These tumors are relatively aggressive. The study noted that the one-year survival rate after a cerebral glioma diagnosis is only 50 percent.

All patients in the study had previously been treated for the tumor using other forms of therapy. The study’s authors concluded that adding hypericin to a regimen of chemotherapy, radiation treatment and surgery may improve the outlook for people with this disease.

Cancer aside, many people take dietary supplements containing St. John’s wort as an attempt to treat their depression, anxiety or insomnia, according to the National Center for Complementary and Alternative Medicine.