Aspartic acid
Sorry, this answer is incorrect. Aspartic acid is not responsible for causing the burn from ants, neither is it found in the leaves of the stinging nettle. Aspartic acid is one of the 20 amino acids that are used for the genetic code. It is a non-essential amino acid and a building block for proteins. Aspartic acid also serves as an excitatory neurotransmitter in the brain and is a metabolite in the urea cycle and participates in the synthesis of glucose. This amino acid is found in large quantities in plant proteins, especially sprouting seeds, dairy, beef, and poultry.