Most amino acids have a chiral center with carboxylic acid and amine functional groups.
Researchers M. P. Tarazona-Diaz, F. Alacid, M. Carrasco, I. Martinez, and E. Aguayo tested the efficacy of L-citrulline on muscle soreness vs. a placebo. For a small group of young male volunteers in an ergometer exercise test, there was determined to be no significant difference in blood lactate concentration during the activity. But after 24 hours, recovery from delayed onset muscle soreness improved subsequent to ingesting 500. mL of natural and enriched watermelon juice.
Watermelon contains an amino acid known as L-citrulline which is also known to be an intermediate in the urea cycle, a biochemical pathway in the liver that enables the body to convert ammonia waste into urea which eventually is eliminated via the kidneys.
L-citrulline
The name comes from citrullus, meaning "watermelon". (http://en.wikipedia.org/wiki/Citrulline)
