**3. Phytochemistry**

all living beings and a secondary metabolism that allows them to produce and accumulate

Most of the carbon, nitrogen and energy ends up in common molecules to all the cells, which are necessary for their functioning and the organisms they belong [26]. These are amino acids, nucleotides, sugars and lipids, present in all plants and performing the same functions. They

Plants allocate a significant amount of assimilated carbon and energy to the synthesis of a wide variety of organic molecules, that do not seem to have a direct function in photosynthetic, respiratory processes, nutrient assimilation, solute transport or protein synthesis, carbohydrates or lipids, and which are called secondary metabolites (also called by-products,

Secondary metabolites are characteristic of superior plants. The essential characteristic of the superior plants is that they possess flower and, consequently, seeds. Its reproductive mechanism is different from that of the inferior ones. They are also called spermatophytes because their reproductive organs are visible and they are subdivided into gymnosperms and

Natural products have biological properties, and they are characterized by their different uses and applications as medicines, insecticides, herbicides, perfumes or dyes, among others. The biosynthesis of secondary metabolites is usually restricted to specific stages of plant development and periods of stress [25]. Some plant cells produce important secondary metabolites of the interactions of the plant with the environment (protection against predators, pathogens or environmental stress) or some related to the reproductive mechanism of the plant (attraction

compounds of diverse chemical nature (**Figure 1**).

28 Phytochemicals - Source of Antioxidants and Role in Disease Prevention

of insects for the promotion of pollination) (**Figure 2**).

are called primary metabolites.

**Figure 1.** The metabolism of plants.

natural products) [27].

angiosperms.

The discipline whose main objective is the study of the chemical constituents of plants is Phytochemistry. The study of such compounds includes: their chemical structures, metabolism (biosynthesis and degradation), natural distribution, biological function, extraction and qualitative-quantitative evaluation. Before starting, any phytochemical analysis is important to have an adequate preparation of our plant material. A practical and simple way of stabilization is by heat treatment, applied, for example, in an oven at a reference temperature of 60°C until the samples reach constant weight; this way, we will make sure that our compounds will be in the optimal conditions to be analyzed.

Phytochemical research of a plant includes several aspects:


In the extraction and purification of organic compounds through the use of solvents, usually follows certain rules based on structural analogies between the substance to be extracted and the solvent that will be used for that purpose.


**Table 1.** Separation and identification techniques.

The polarity of the compounds is another element to be taken into account, when considering the solubility of a solute in a given solvent. Thus, strongly polar solvents dissolve ionic or highly polar solutes, while low-polar solvents do not efficiently dissolve ionic solutes but do dissolve low-polarity solutes.

The extraction of the vegetal material is done consecutively using solvents, from a low polarity until reaching the water, which is the most polar solvent.

The obtained extracts can be clarified by filtration through celite with a vacuum pump and then concentrated under reduced pressure. This is generally carried out in a rotary evaporator, in which the solutions are concentrated until a volume reduction is achieved, at temperatures between 30 and 50°C. The concentrated extracts must be stored refrigerated.

In the separation and identification of natural products, different techniques for isolation and identification have been developed, in **Table 1** is a summary of the main techniques.
