Ectoine

Ectoine (1,4,5,6-tetrahydro-2-methyl-4-pyrimidinecarboxylic acid) is a natural compound found in several species of bacteria. It is a compatible solute which serves as a protective substance by acting as an osmolyte and thus helps organisms survive extreme osmotic stress. Ectoine is found in high concentrations in halophilic microorganisms and confers resistance towards salt and temperature stress. Ectoine was first identified in the microorganism Ectothiorhodospira halochloris, but has since been found in a wide range of Gram-negative and Gram-positive bacteria. Other species of bacteria in which ectoine was found include:
 * Brevibacterium linens
 * Halomonas elongata
 * Marinococcus halophilus
 * Pseudomonas stutzeri
 * Halomonas titanicae
 * Halorhodospira halophila
 * Halomonas ventosae

Biosynthesis
Ectoine is synthesized in three successive enzymatic reactions starting from aspartic β-semialdehyde. The genes involved in the biosynthesis are called ectA, ectB and ectC, and they encode the enzymes L-2,4-diaminobutyric acid acetyltransferase, L-2,4-diaminobutyric acid transaminase and L-ectoine synthase, respectively.

Use in cosmetics
Ectoine is used as an active ingredient in skin care and sun protection products. It stabilizes proteins and other cellular structures and protects the skin from stresses like UV irradiation and dryness.

Medical use
Due to its protein stabilizing properties, ectoine has been evaluated as a topical treatment for hay fever. Effectiveness of a nasal spray containing ectoine is comparable to cromoglycate and is reported to be well tolerated by the patients. It is available over-the-counter in European Union.