**2. Phytosterols (DESM, MMS, DIM)**

Phytosterols also called plant sterols, are minor components of vegetable oils and from a major proportion of the unsaponifiable fraction of lipids which can occur in vegetable oils either in free form or esterified with fatty acids [4]. The individual sterols and their relative proportions can be used to determine the identity of the oil and to detect adulterations. Phytosterol contents in vegetables are known to vary due to different factors such as variety, season, extraction, and other technological procedures [5].

Furthermore, phytosterols are known to lower serum mow-density lipoprotein (LDL). Cholesterol levels by reducing intestinal cholesterol absorption. Clinical studies confirmed that phytosterols have hypocholesterolemy, anti-inflammatory and anticarcinogenic effects [5]. Therefore, phytosterols have been added to several functional food products such as yoghurt, milk and some vegetable oils. These types of products are now available on the market and have been scientifically proven to lower blood LDL cholesterol by around 10–15% as part of a healthy diet [5].

#### **2.1 Structure**

Phytosterols (PS) are by-products of the isoprenoid biosynthetic pathway via squalene from acetyl-coenzyme A [6]. They are 28or 29-carbon alcohols and resemble cholesterol in vertebrates in term of both functions, i.e. by stabilization of phospholipids bilayers in plant cell membranes as in structure, given the four-ring steroid nucleus, the 3β-hydroxyl group and often a 5, 6-double bond (**Figure 1**) [7].

They have been categorized into three subclasses: on the basis of the number of methyl groups at the C4 position: (4-DEMS) none (4-desmethylsterols or "sterols"), (4-MMS) one (4α-monomethyl-), and (4-DIMS) two (4,4′-dimethylsterols or triterpenes alcohols) [8, 9]. The main compounds of 4-desmethylsterols class are β-sitosterol, campesterol, stigmasterol and ∆<sup>5</sup> - avenasterol (**Figure 2**). 4,4′-dimethylsterols (triterpenes alcohols) and 4α-monomethylsterols are metabolic intermediates in the biosynthetic pathway leading to the end-product, 4-desmethylsterols, but they are usually present at lower levels than 4-desmethylsterols in most plant tissues [8–11]. The major components of 4,4′-dimethylsterols are β-amyrin, α-amyrin, cycloartenol and 24-methylencycloartanol (**Figure 2**). In the case of 4α-monomethylsterols, we evoke mainly Obtusifoliol, gramisterol and citrostdienol (**Figure 2**). Generally, plant sterols are 4-desmethylsterols because they do not contain any methyl groups at the fourth position of the sterol ring structure [12].

*Oilseeds as Functional Foods: Content and Composition of Many Phytochemicals… DOI: http://dx.doi.org/10.5772/intechopen.97794*

*Steroid structure.*

*Detailed chemical structures of b-sitosterol, Campesterol, Stigmasterol, D5 -avenasteroland and D7 -avenasterol.*

#### **2.2 Plants as source of phytosterols**

Vegetable oils, oilseeds, and nuts are the richest sources of phytosterols. β-sitosterol (29C), campesterol (28C) and stigmasterol (29C) are the most common sterols [4, 12]. The total PS content and profile can vary according to variety, agronomic and climatic conditions, maturity, extraction and refining methods [13, 14].

The impact of cultivar on seed oils phytosterols content was demonstrated and many major phytosterols components were identified on some seed oils of commercial importance such as rapeseed, soybean, and sunflower have been regarded as rich sources of phytosterols [15].

#### *2.2.1 Health benefits*

Several studies have demonstrated the PS protect against many chronic ailments such as cardiovascular diseases [16, 17], cancer [18], ulcers [19], diabetes [20], and inflammation [21].

4-desmethylsterols contribute to lowering serum cholesterol levels [22]. In fact, it have been reported that they have the capacity to reduce dietary cholesterol absorption in the intestine [22]. They are also considered to have anti-inflammatory, anti-bacterial, anti-atherosclerotic, anti-oxidative, anti-ulcerative, and anti-tumor properties in humans [8–23], as well as contributing to the oxidative and thermal stability and shelf-life of vegetables oils [24]. In vivo studies have shown that diets enriched with PS (2%, w/w) contributed to improve lipid profiles and decreased atherosclerotic lesions in apolipoprotein E-knockout (apoE-KO) mice [20]. In addition, they are useful emulsifiers for cosmetic manufacturers and supply most steroidal intermediates and precursors to produce therapeutic steroids [25].

PS have been reported to have a protective effect against various forms of cancer such as breast [21], prostate [26], lung [4], liver and stomach [27], and ovary and colon cancers [28].

Triterpenes compounds are also important bioactive secondary metabolites, due to the wide range of their biological activities. They show mainly antimicrobial, cytotoxic, antitumoral, antiviral, anti-inflammatory- hepatoprotective, antifeedant and insecticidal activities [29].

#### **3. Phenolic acid**

Phenolic phytochemicals are the most abundant secondary metabolites and the most widely distributed in the plant kingdom. The three most important groups of dietary phenolics are flavonoids, phenolic acids, and polyphenols (tannins, stilbenes and lignans) [30].

Phenolic are hydroxyl group (-OH) containing class of chemical compounds where the (-OH) bonded directly to an aromatic hydrocarbon group. Phenol (C6H5OH) is considered the simplest class of this group of natural compounds. Phenolic compounds are a large and complex group of chemical constituents found in plants [31]. They are plant secondary metabolites, and they have an important role as defense compounds. Phenolics exhibit several properties beneficial to humans and its antioxidant properties are important in determining their role as protecting agents against free radical-mediated disease processes.

#### **3.1 Structure**

They are defined as chemical substances possessing one or more aromatic rings with one or more hydroxyl groups in their structures [32].

The term "phenolic acids" (PA), in general, designates phenols that possess one carboxylic acid functional group. Naturally occurring phenolic acids contain two distinctive carbon frameworks: the hydroxycinnamic and hydroxybenzoic

*Oilseeds as Functional Foods: Content and Composition of Many Phytochemicals… DOI: http://dx.doi.org/10.5772/intechopen.97794*

structures (**Figure 3**). Hydroxycinnamic acid compounds are produced as simple esters with glucose or hydroxy carboxylic acids. Plant phenolic compounds are different in molecular structure and are characterized by hydroxylated aromatic rings [33]. These compounds have been studied mainly for their properties against oxidative damage leading to various degenerative diseases, such as cardiovascular diseases, inflammation, and cancer. Indeed, tumor cells, including leukemia cells, typically have higher levels of reactive oxygen species (ROS) than normal cells so that they are particularly sensitive to oxidative stress [34]. Many papers and reviews describe studies on bioavailability of phenolic acids, emphasizing both the direct intake through food consumption and the indirect bioavailability deriving by gastric, intestinal, and hepatic metabolism [35]. In addition, Phenolic acid compounds and functions have been the subject of a great number of agricultural, biological, chemical, and medical studies. In recent years, the importance of antioxidant activities of phenolic compounds and their potential usage in processed foods as a natural antioxidant compounds have reached a new level and some evidence suggests that the biological actions of these compounds are related to their antioxidant activity [36].
