Study of Essential Oils Obtained from Tropical Plants Grown in Colombia DOI: http://dx.doi.org/10.5772/intechopen.87199

eucalyptus), or in the trichomes (many plants of Labiatae, Asteraceae, Solanaceae, Geraniaceae families). The plant material (aromatic plant), when subjected to water vapor, releases a liquid odoriferous mixture (EO) of various volatile substances; this mixture can have from 50 to more than 300 chemical substances and is composed of terpene hydrocarbons, their oxygenated derivatives, alcohols, aldehydes, and ketones, as well as ethers, esters, phenolic compounds, phenylpropanoids, and other derivatives [3].

EOs can be obtained from plant material by three main methods (Figure 1). (1) Steam distillation. This process is carried out with a superheated dry steam, usually generated by a boiler or steam generator, which penetrates the plant material at higher than atmospheric pressure; the steam current breaks the cells or oil channels in the plant and drags the volatile mixture, which condenses after passing through a cooling system (heat exchanger). Generally, the oils are lighter than water and with very little soluble in it; therefore, they can be separated by decantation. The exception is the clove oil, which is heavier than water and is collected under it. The steam distillation method is used to extract oils from rhizomes, roots, seeds (vetiver, valerian, ginger, anise, cardamom, etc.), and dried or fermented leaves of some plants (e.g., patchouli). (2) Distillation with watersteam. In this extraction system, wet steam is used, coming from the boiling water, which passes through the plant material suspended above and supported on a mesh. Most herbaceous plants are distilled by this method. (3) Hydro-distillation is a process in which the plant material is directly immersed in water, heated to a boil. This method is used for the distillation of more delicate plant material, for example, flowers (e.g., ylang-ylang, roses). The citrus peel (orange, tangerine, lime) EOs are also obtained by cold-pressing or by scraping their surfaces. The mixtures obtained by the methods mentioned above are called "essential oils"; other products, isolated by maceration in different solvents or with supercritical fluid (CO2), are generally called "extracts" and not "oils"; among them are concrete—obtained

Figure 1. Main methods of essential oil isolation.

essential oils for export or the national market. Brazil, India, China, Indonesia, and the United States are Colombia's main essential oil suppliers. In 2017, the total cost of the country's essential oil imports was 14.289 million dollars, while the country exported just 298 thousand dollars [2]. Since there is no essential oil production, the EO exported amounts corresponded to commercialization of previously

The publication of Colombian scientific articles on EO research started in 1974 and grew slowly during the following 30 years (less than three articles per year). The transition point was marked by the creation in 2005 of a network of research groups that joined their expertise around the development of the EOs agroindustry. The Research Center of Excellence for the Agroindustrialization of Aromatic and Tropical Medicinal Species (CENIVAM), under technical and administrative coordination at the Industrial University of Santander (Bucaramanga), has been a leader in aromatic plants and EO studies in Colombia for more than a decade. Over 250 scientific articles comprise the results of its investigations, which have been focused on the multidisciplinary and systematic search of promising native plants and on introduced species such as ylang-ylang, palmarosa, turmeric, patchouli, mints, basils, citrus, geraniums, and others. Researchers from more than 10 universities have carried out their work in areas of botany and taxonomy, plant physiology, and

ecology; on the study of secondary plant metabolites, crop and post-harvest improvement, EO distillation and its optimization, and design of rural stills; on the study of volatile fractions from plants and flowers, obtainment of extracts with solvents and supercritical fluids (SFE-CO2), and catalytic transformation of EOs or their main components; and on the study of their diverse biological properties

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

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,

(antioxidant, antimicrobial, insecticidal, antiviral, and others).

imported oils.

Essential Oils - Oils of Nature

2. Essential oil isolation

for their perception.

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by extraction with hydrocarbons from aromatic plants or, more frequently, flowers —and absolutes, which are separated from concrete or pomade (obtained by enfleurage) by alcohol.

involved in each project, 3 or 4 plant species cultivated per unit (palmarosa, citronella, Lippia origanoides, L. alba, rosemary, or thyme), plant nurseries, and the facilities for EO extraction in the field. Several rural stills (1 m<sup>3</sup> retort capacity) have been designed and built by CENIVAM. A mobile autonomous version that uses a radiator as condenser received a patent [4]. The farmers are trained on good agricultural practices, post-harvest treatment, and steam distillation. All activities are accompanied by permanent technical assistance (Figure 2). These small rural projects constitute an opportunity for a commercializing enterprise that consolidates the various producers around quality control guidelines and provides the technical support to connect them with buyers abroad. The university provides the technical support for chemical characterization with modern instrumentation, production of

Study of Essential Oils Obtained from Tropical Plants Grown in Colombia

The analytical technique routinely used for the instrumental chemical analysis of

The GC can have conventional, e.g., flame ionization detector (FID), or thermal conductivity detector (TCD), and spectral detectors can have an external device attached, for example, a headspace sampler, a pyrolyzer, a purge and trap (P&T) system or a thermal desorption setup, among others. Each block of the chromatographic system has its own function and its "responsibility" for the quality of the analysis and the results obtained; for example, the function of the injection system is to transfer the sample to the column quantitatively, without discrimination by molecular weight or by the volatility of the components and without their chemical alteration (decomposition, isomerization, or polymerization) (Figure 3). The "responsibility" of the chromatographic column in the EO analysis is high: the clear, complete (ideally) separation of all the components of the mixture must be accomplished. The separation is based on achieving different distribution constants of the components between the two phases, stationary and mobile. This is obtained by establishing the optimal operational conditions (temperature, type of mobile phase, its velocity, stationary phase polarity, carrier gas pressure, temperature program, etc.) (Figure 4) and by correctly choosing the chromatographic column, i.e., its dimensions (length, internal diameter), chemical composition of stationary phase, its polarity and thickness, and among other factors. For the EO analysis, long columns (50 and 60 m) are used, since the oils are complex multicomponent mixtures and, above all, they have structurally very similar compounds (isomers), which require that the column has a very high resolution, which, among other factors, is achieved by increasing its length. The EOs contain compounds of very different polarities, both nonpolar (terpene hydrocarbons) and polar (alcohols, aldehydes). This implies that for their analysis, columns with different stationary

The detection system differentiates the analyte molecules from those of the mobile phase (carrier gas), to which the detector is transparent. The response of the

EOs is gas chromatography (GC), because the constituents of oils are volatile (monoterpenoids, esters, etc.) or semi-volatile substances (sesquiterpenoids, phenolic derivatives, etc.), whose molecular masses and boiling points do not exceed 300 a.m.u. and 300 °C, respectively. A chromatographic system comprises four fundamental blocks: (1) sample introduction system (injector), (2) separation system (column), (3) detection system for analytes eluted from the column (detector),

technical data sheets, and quality assurance.

DOI: http://dx.doi.org/10.5772/intechopen.87199

and (4) data analysis and operation control system.

3. Essential oil characterization

3.1 Gas chromatographic analysis

phase polarities will be required.

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The EO industrial production involves field distillation, in order to avoid the high transportation costs of large vegetal material loads from which only about 1% is going to be obtained as EO. Steam generation is one of the main components of the operation costs. Current trends point toward the use of lignocellulosic waste as biofuel for the furnace. Still capacity is determined by the crop size. The goal is to maintain the still operating for at least 300 days of the year and to schedule the harvests to avoid long storage (more than a week) of the cut vegetal material waiting for its distillation. This is mainly to prevent mold formation. Patchouli and vetiver are two exceptions to this rule, because a curing period of several days or months (vetiver) recommended to enhance oil yield and organoleptic quality.

The reality is that a large part of Colombian small growers have low purchasing power, low economic performance and productivity, and not very sophisticated technology level in rural operations and processes. Traditional agricultural production faces a complex problem that includes low prices, low profitability, and the increasingly acute lack of rural labor, because young people migrate to the cities. The EO industry is a very important rural development alternative in which the harvested vegetal material is no longer the final product, but the start of an addedvalue product chain. Several pilot projects, financed by the Ministry of Agriculture and Rural Development and Colciencias (Colombia's Science Funding Agency), have been carried out in the past 15 years by CENIVAM with the participation of small rural farmers associations. The common goal of these projects has been the development of the EO value chain. The economic, agronomic, and quality viability of EOs obtained in several productive units have been studied. Each unit has characteristics, as follows: 5–8 ha crop extension, 20–22 families of small growers

Figure 2. Rural production and distillation of essential oils in Colombia (Barbosa, Santander).

Study of Essential Oils Obtained from Tropical Plants Grown in Colombia DOI: http://dx.doi.org/10.5772/intechopen.87199

involved in each project, 3 or 4 plant species cultivated per unit (palmarosa, citronella, Lippia origanoides, L. alba, rosemary, or thyme), plant nurseries, and the facilities for EO extraction in the field. Several rural stills (1 m<sup>3</sup> retort capacity) have been designed and built by CENIVAM. A mobile autonomous version that uses a radiator as condenser received a patent [4]. The farmers are trained on good agricultural practices, post-harvest treatment, and steam distillation. All activities are accompanied by permanent technical assistance (Figure 2). These small rural projects constitute an opportunity for a commercializing enterprise that consolidates the various producers around quality control guidelines and provides the technical support to connect them with buyers abroad. The university provides the technical support for chemical characterization with modern instrumentation, production of technical data sheets, and quality assurance.
