Wikipedia
Reuterin is a potent antimicrobial multi-compound produced by Lactobacillus reuteri, during the metabolism of glycerol to 1,3-propanediol catalysed by the coenzyme B12-dependent diol dehydrase. Reuterin consists of 3-hydroxypropionaldehyde, its hydrate, and its dimer in dynamic equilibrium. At concentrations above 1.4 M, the HPA dimer is predominant; at concentrations relevant for biological systems, however, HPA hydrate is the most abundant, followed by the aldehyde form.
Reuterin inhibits the growth of some harmful Gram-negative and Gram-positive bacteria, along with yeasts, molds, and protozoa. L. reuteri can secrete sufficient amounts of reuterin to inhibit the growth of harmful gut organisms, without killing beneficial gut bacteria, allowing L. reuteri to remove gut invaders while keeping normal gut flora intact.
Reuterin is water-soluble, effective in a wide range of pH, resistant to proteolytic and lipolytic enzymes, and has been studied as a food preservative or auxiliary therapeutic agent.