The plant contains an alkaloid poison which is similar to the nightshade variety of plants that were native to Earth, and had a chemical structure similar to plants from many class M planets. The plants were originally discovered by Professor Robert Crater in 2261, and experiments on the plant revealed that the roots poisonous properties were only a danger to mice. The plant was also known to produce a pleasent odor which was similar to tapioca.
In 2266, the M-113 creature, posing as Nancy Crater, blamed the death on USS Enterprise crewman, Scott Darnell, on him having eaten a piece of Borgia plant. However, this statement was later proven to be false by Commander Spock and Dr. Leonard McCoy. (TOS episode & novelization: The Man Trap)