2. Essential oil isolation

The primary metabolites (proteins, lipids, sugars, etc.) in plants are vital for the plant to grow, multiply, and live, while secondary metabolites are required by the plant to survive. For sure and with all the experimental details studied, the role played by secondary metabolites in plants is not completely known, because they fulfill several functions and operate through different mechanisms. Among many secondary metabolites isolated from plants, there are some very special, widely used in various branches of industry, medicine, and in many products of everyday life. This class of substances is called EOs, volatile oils, ethereal oils, or essences. Numerous substances are part of these oils; they are a complex mixture of volatile compounds with very diverse chemical nature. What most characterizes and highlights them is their smell, generally pleasant and intense, that evokes the fragrance of the plant or of the fruit or wood, from which these oils come. The essence can be remembered as the smell, for example, of a freshly cut grass or vanilla, sweet and cloying, among other aromatic tones that an EO has, formed by a complex range of volatile substances with different fragrant notes and different sensory thresholds for their perception.

Isolated from flowers (rose, orange blossom, lily, ylang-ylang), seeds (coriander, celery, carrot, anise, cardamom), leaves and stems (basil, thyme, mint, lavender, oregano), bark (cinnamon), wood (pine, sandalwood), roots (valerian, vetiver), and rhizomes (ginger, turmeric). EOs can be considered as the soul of the plants, their spirit, which characterizes, highlights, evokes, and makes them memorable in time; oils, generally, produce a pleasant sensation, especially when diluted. The EOs in the plants can be found in the different oil cells (ginger, turmeric, vanilla), in the secretory channels (pine, artemisia, anise, angelica), in the glands (citrus,
