α-Carotene is the second common form of the orange photosynthetic pigment, carotene (β-carotene is the most common), and possesses a β-ring at one end and an ε-ring at the other. Humans and other mammals can produce retinal (a form of Vitamin A) from the retinyl group(β-ionone ring) of α-carotene, though its activity in this role is less than that of β-carotene, which has two retinyl groups. α-carotene is found in high concentrations in yellow-orange vegetables, such as carrots and squash, and dark-green vegetables, such as broccoli and spinach. High blood levels of α-carotene in adults has also been recently linked to lower mortality rates. It is useful as a control for HPLC.
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