There are two types of carotenoids:
(a)Carotenes : They are hydrocarbons with a general formula of C40 H56. The most common carotene is |3-carotene which converted to vitamin A by animals and human beings.
C40H56 + 2H20—+ 2C19H27CH2OH Vitamin A
(b)Xanthophylls : They are oxygen containing derivatives of carotenes e.g., C40H56O
(cryptoxanthin),C40H56O2 (lutein, zeaxanthin).