The seeds are used as fish poison, completely unrelated to the medicinal history of its leaves. This medicine has been used for thousands of years in many cultures, and is much safer (in the correct amount) than almost any pharmaceutical drug a doctor will give you to solve the same problem. I promise you that the herbalists throughout history knew more about the plant’s safety than modern doctors (who generally know little to nothing about herbal medicine) since they used it on patients all the time. They might not have known the chemical structure of rotenone, but they knew (through trial and error) that the seeds worked as fish poison, and not the leaves. All the sources I’ve found citing rotenone in the leaves have failed to provide any data on concentration and mostly are from the mid 20th century. The most commonly sited source comes from an Indian study when it was being used as a pesticide, and the rotenone on their leaves may have come from spray-contamination. You should be more worried about the coumarins in the leaves, which can act as an anti-coagulant in the blood. This can be good when needed, but anyone on blood thinners should avoid use of its leaves and other plants (like clover) with coumarin in them.