**5.2 Plants as source for carotenoids**

Carotenoids distribution in plants is associated with the de novo synthesis that occurs in the differentiated plastids of roots, flowers, fruits, and seeds. Their accumulation can be subdivided as chloroplasts (green plastids), chromoplasts (yellow, orange, and red plastids), amyloplasts (plastids containing starch), elaioplasts (lipid containing plastids), leucoplasts (colorless plastids), and etioplasts (darkmatured precursors of the chloroplast) [53].

**Figure 5.** *Structure of the important naturally occurring carotenoids.* *Oilseeds as Functional Foods: Content and Composition of Many Phytochemicals… DOI: http://dx.doi.org/10.5772/intechopen.97794*

Because plants can synthesize carotenoids de novo, they are widely distributed in plant-derived foods and the composition is enriched by the presence of small amounts of biosynthetic precursors and derivatives of the major carotenoids. In general, the level of carotenoids is directly proportional to the intensity of color. Egg yolks, dairy products, fruits, vegetables, legumes, grains and seeds are their major food sources. In green leafy vegetables, b-carotene is predominant while in the orange-colored fruits and vegetables such as carrots, apricots, mangoes, yams, winter-squash, other carotenoids typically predominate. Yellow vegetables have higher concentrations of xanthophylls with a low provitamin A activity, but some of these compounds, such as lutein, may have significant health benefits. The red and purple vegetables and fruits such as tomatoes, red cabbage, berries, and plums contain a large portion of non-vitamin A active carotenoids. Tomato and watermelon are major sources of lycopene [53].

Higher plant usually contains similar carotenoids; however, their distribution differs quantitatively. It is known that the oil with the highest carotenoid content is crude palm oil (500-700 mg/100 g of oil). Carotenoid's content of the other crude vegetable oils is below 100 mg/100 g of oil [38].

#### **5.3 Health benefits**

Carotenoids, another group of lipid-soluble compounds synthesized by plants, are also strong antioxidants in addition to functions in plants' photosynthesis. Carotenoids are also essential to human health. More than 700 carotenoids have been identified in plant foods and human body, but the overwhelming majority (90%) in human diet is represented by β- carotene, α-carotene, lycopene, lutein, cryptoxanthin and zeaxanthin [51].

Carotenoids are characterized by a high reactivity due to their system of conjugated double bonds. They can readily suffer chemical transformation being oxidized by reactive species to a number of compounds. After ingestion, carotenoids suffer a series of modifications in the organism, namely through the reaction with reactive oxygen and nitrogen species (ROS and RNS, respectively). Interestingly, the way carotenoids react with ROS and RNS seems to depend on different factors, namely concentration of carotenoids, oxygen pressure, presence of other antioxidants, etc. Moreover, these factors may imply variations of the redox properties of carotenoids and of the oxidation products formed. These compounds, designed as oxidation products, are not yet fully studied and/or identified in biological tissues, but there are some studies relating them with the growth of several cancer cells and to oxidative effects. The increase of knowledge in this field seems to be truly important to establish the real impact of carotenoids and their oxidation products in human health [53]. Studies have shown that antioxidant carotenoids have protective effects against skin disorders, eye disorders, cancer, and cardiovascular diseases [54].

Carotenoids in oils play important role in the stability of the oil as a singlet oxygen quencher in addition to their coloring properties [55]. Carotenoids, together with PA and tocols, are involved in the oxidative stability of oils and have synergist antioxidant effects [56].

#### **6. Conclusion**

Oilseeds, like other plant sources, provide an important reservoir of myriad of phytochemicals. However, little has been researched about the relationship between ripening index of the seed bearing and oil fatty acids, bioactive compounds, and

## *Functional Foods - Phytochemicals and Health Promoting Potential*

antioxidant activity. This should be considered to have a clearer understanding of the preharvest effect on seed oil nutritional qualities and antioxidant properties. For instance, the drying time of seeds would have a considerable effect on extracted oil quality. In view of the thermolabile nature of bioactive compounds such as tocopherols and polyphenols, the effect of seed drying and pretreatments for seed drying on oil antioxidant compounds and capacity deserves more research. This would assist in quantifying losses of bioactive compounds losses and instituting preventive measures at this stage of seed oil processing.
