300 OLIVE OILS AND HEALTH ce agents and are therefore particularly abundant in the bark of stems and in the cuticular waxes on the surface of leaves and fruits. Among these, the most studied are the triterpenic acids, which contain a carboxyl group. Notable examples include the maslinic, oleanolic, and ursolic acids. Another subgroup are the triterpenic dialcohols, which are pentacyclic triterpenes based on the β-amyrin skeleton, where one hydrogen atom of the methyl group at position 28 is replaced by a hydroxyl group. In olive oil, the most prominent are erythrodiol and uvaol. These compounds are known for their health-promoting properties and are frequently used as ingredients in dietary supplements. - phytosterols Phytosterols are the plant homologues of cholesterol in animals. These natural plant sterols are composed of 28 or 29 carbon atoms and have a structure very similar to that of cholesterol. They are the most abundant group of compounds in the unsaponifiable fraction of vegetable oils. Their skeleton consists of four rings (three six-carbon rings arranged in a non-linear fused structure with a five-carbon ring) with a flexible side chain. Phytosterols may exist in either free or esterified form. The main sterols in olive oil are β-sitosterol, Δ5-avenasterol, stigmasterol, and campesterol. Their main effect is to inhibit cholesterol absorption in the intestine. However, the amounts present in food are generally insufficient to significantly reduce high blood cholesterol levels. Phytosterols also help regulate cell membrane permeability and enzyme activity. - phytostanols Phytostanols are the reduced forms of phytosterols. Like their precursors, they are of plant origin and have a structure very similar to cholesterol. They help lower total plasma cholesterol without affecting HDL-cholesterol levels and are considered beneficial in the prevention of cardiovascular diseases. - squalene Squalene is a natural organic compound found in certain plants such as rice and olives, and is notably present in olive oil as part of its minor components. It is produced by all complex organisms, including humans. Its name derives from its original identification in shark liver (Squalus genus). Chemically, it is a polyunsaturated hydrocarbon from the triterpenoid family, with six double bonds. It is a viscous, clear, and odourless oil. Squalene is known for its antioxidant and antitumour properties. MINOR FRACTION (See MINOR COMPOUNDS) MITOCHONDRIA/S The cell is the morphological and functional unit of all living organisms. Every cell consists of three main parts: the cell membrane, the cytoplasm, and the nucleus. The cell membrane forms the outer layer of the cell, enclosing and defining its boundaries. Inside, the cytoplasm fills the space between the cell membrane and the nucleus. It is a fluid with a grainy appearance and contains the organelles, small structures with specific functions, such as mitochondrias. Most biochemical reactions and most protein synthesis take place in the cytoplasm. The nucleus, which is also surrounded by its own membrane (the nuclear membrane), contains the chromosomes, where most of the cell’s genetic material is located.
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