Menispermum canadense or Moonseed
A vine, native to eastern North America, found from southern Ontario all the way to northern Florida. It can be found in thickets, moist woods, and around streams. This plant is poisonous when consumed. The fruit is toxic and fatal due to the principal toxin: alkaloid dauricine.
Alkaloid dauricine is a plant metabolite that is a naturally occuring organic compound developed by the plant itself.