In vivo and in vitro approaches demonstrate proline is not directly involved in the protection against superoxide, nitric oxide, nitrogen dioxide and peroxynitrite.

Plants accumulate proline under diverse types of stresses, and it has been suggested that this α-amino acid has the capacity to protect against oxidative stress. However, it is still controversial whether its protection is due to the direct scavenging of reactive oxygen species (ROS). To solve this issue and considering that nitrosative stress is directly related with an oxidative stress condition, we evaluated whether proline can protect against nitrosative damage.