**2. Chemistry of carotenoids and their dietary sources**

Carotenoids can be found in a variety of foods, although the majority of carotenoids in the diet are derived from strongly colored vegetables, fruits, and juices. Carotenes supplied as food colorings to foods during the process, milk and dairy fatcontaining meals, eggs, seafood, and carotenoids provided as food colorings to foods during handling can also supply trace amounts. The principal sources of carotenoids in the United States are shown in **Figure 1**. The data is derived from Median values using current HPLC procedures [20].

B-cryptoxanthin is present in orange fruits, lutein in green leafy vegetables, and lycopene in tomatoes and tomato derivatives, while B-carotene and a-carotene are both found in yellow-orange veggies and fruits. Multicomponent or mixed meals (e.g., soup, stew) generally contain a considerable proportion of carotenoid-rich foods, which is a practical element to address in dietary evaluation [21, 22]. Seasonality may be a key factor of the kind and amount of dietary carotenoids consumed in populations or cultural groups that consume fruits and vegetables in seasonal patterns [23, 24]. Most carotenoids have a polyisoprenoid structure, which means they have a lengthy connected network with the double bonds and are essentially bilaterally symmetrical around the central doubled bond [25]. Multiple carotenoids are generated by cyclizing the end groups and adding oxygen functionalities to the basic structure, which gives them their distinctive hues and antioxidant characteristics. The structure of several carotenoids is shown in **Figure 2**.

**Figure 2.** *Chemical structure of common carotenoids.*
