tétraterpénoïdes

Tétraterpénoïdes are a class of organic compounds derived from the isoprenoid pathway. They are characterized by their structure, which is formed from four isoprene units, hence the prefix "tétra-". These molecules are found widely in nature, particularly in plants, algae, and bacteria. The basic building block of tétraterpénoïdes is isopentenyl pyrophosphate, which undergoes a series of enzymatic reactions to form prenyl pyrophosphate, then geranyl pyrophosphate, farnesyl pyrophosphate, and finally geranylgeranyl pyrophosphate. Two molecules of geranylgeranyl pyrophosphate then condense head-to-head to form phytoene, a C40 carotenoid precursor.

The most well-known group of tétraterpénoïdes are the carotenoids. Carotenoids are pigments responsible for the yellow, orange, and red colors seen in many fruits, vegetables, and flowers. They play crucial roles in photosynthesis as accessory pigments, absorbing light energy and transferring it to chlorophyll. Furthermore, many carotenoids, such as beta-carotene, are important antioxidants and can be converted into vitamin A in animals, making them vital for vision, immune function, and cell growth. Other examples of tétraterpénoïdes include xanthophylls, which are oxygenated carotenoids, and lycopene, the pigment found in tomatoes. The structural diversity of tétraterpénoïdes arises from variations in the number and arrangement of isoprene units, as well as the presence of oxygen-containing functional groups and ring structures. Their biological significance extends beyond pigmentation and antioxidant activity, with some tétraterpénoïdes also involved in signaling pathways and UV protection.