MOLECULE

Carotene

Alpha carotene belongs to the group of compounds known as carotenoids. More specifically carotenoids are classified as tetraterpenoids, being built from four terpene units (8 isoprene units) each containing 10 carbon atoms. As a result, carotenoids typically have a total of 40 carbon atoms. They are characterized by the presence of two end-groups (mostly cyclohexene rings, but also cyclopentene rings or acyclic groups) linked by a long-branched alkyl chain. There are more than 1100 known carotenoids. Carotenoids can be further categorized into two classes, xanthophylls (which contain oxygen) and carotenes (which are purely hydrocarbons and contain no oxygen). Carotenoids are among the most common pigments in nature and are natural lipid soluble antioxidants. Alpha-carotene is one of the primary isomers of carotene, although Beta-carotene is the most abundant. There are six known carotene isomers including α-, β-, γ-, δ-, ε-, and ζ-carotene. These carotene isomers contain unsubstituted beta-ionone rings, which means they can be readily converted to retinol and vitamin A. In other words, they have pro-vitamin A activity. Alpha-carotene has less vitamin A activity than Beta-Carotene. This is because of its structure, as Alpha-carotene it is converted to just one molecule of biologically active retinol after central cleavage, while Beta-carotene is converted to two molecules after cleavage. Plants, fungi, and photosynthetic bacteria synthesize carotenes, while animals must obtain them as a dietary nutrient. In plants carotenes contribute to photosynthesis by transmitting the light energy they absorb to chlorophyll. They also protect plant tissues by helping to absorb the energy from singlet oxygen, an excited form of the oxygen molecule O2 which is formed during photosynthesis. Alpha-carotene is a very hydrophobic molecule, practically insoluble in water, and relatively neutral. Alpha-carotene is found in many common orange-, yellow-, and green-colored fruits and vegetables such as carrots, pumpkins, squash, apricots, sweet potatoes, and beans. The concentration of α-Carotene is especially high in orange carrots and high serum concentrations are associated with high carrot intake. Other plants and foods that have high levels of alpha-carotene include cloves, shallots, cumin, wolfberries, cantaloupes, papaya, spinach, broccoli, turnip, avocado, green peas, orange and red peppers, and tomatoes. Alpha-carotene (along with beta-carotene) exhibits numerous beneficial health or pharmacological properties including antioxidant, anti-obesity, anti-cancer, anti-aging, anti-atherosclerotic and anti-sunburn properties as well as hepatoprotective, neuroprotective and improved vision and night blindness prevention ( PMID: 27047317). Alpha-carotene is one of a small number of pigments including (beta-carotene and xanthophylls) found in cannabis plants. It was first isolated from hemp leaves and identified as a cannabis constituent in 1969 (PMID: 6991645).