Frontiers in Horticulture

Plants produce useful substances for human health and care. These compounds are usually secondary metabolites, which do not have a direct function in the development and growth of the plant, but help the plant interacting with its environment. They are produced by certain tissues and cells, during specific stages of the plants or at different moment of their living cycle. They act as insects attractive (for example for pollination) or repellent agents, as a defence from extreme weather conditions (drought, freezing), to avoid growth of unwelcome plants (allelopathy), or to combat bacteria and viruses. The useful part is called plant drug, and it can be the whole plant or a part of it. These active principles can be extracted by distillation, solvent extraction, pressure or other methods, depending on to their chemical characteristics. The demand for these plants and the related products is nowadays increasing worldwide, and some of them are becoming scarce in some areas due to wild harvesting. In Europe, the demand for instance for food supplements, is going to grow, for our health care needs and demands are changing. In fact, MAPs for medicinal use represent the highest number of plant species used by humans, as they provide most of the medicinal ingredients in many health care traditional systems. But these plants are not only used for medicines. Their use in the cosmetic and perfumery, food and liquor industries is well known, as well as other uses as natural pesticides, dyes, tannins, etc.

Pharmacological activity in plant-based drugs is centred on the presence of chemical compounds which we call active compounds. Active components are substances which are found in different parts and organs of plants, which change or modify the functions of human and animal organs and systems. There is a huge variety of active components, of which the most important are secondary metabolites such as essential oils, alkaloids, glycosides and phenolics. There are many classifications but we will use the following classification in four groups according to chemical structure: glycosides, phenolics, terpenoids, and alkaloids. These in turn are sub-divided into other groups according to their chemical structure. In this chapter, a classification, description function and examples of these active compounds is presented. We will make reference to secondary metabolites only, due to their significance as a source for active ingredients.

Plants generate a considerable amount of antioxidants, preservatives, and synthetic colours. There is much demand for these in the cosmetics industry. The perfume sector also uses important quantities of aromatic plants. The dermatological properties of plants are many and varied: tonics, astringents, anti-inflammatory, antiseptics, anti-scarring, cleansers, moisturisers, relaxants, emulsifiers, decongestant, refreshing, etc. The use of different plants is determined by their physiological activity, which varies from plant to plant, so it is possible to find a plant for nearly all our aesthetic needs. There is also a wide range of formats of cosmetic preparations. We can find preparations of plant extracts in creams, emulsions, lotions, gels, oils, soaps, deodorants, etc. Regulations regarding these products apply to raw materials for use in cosmetics. They also refer to the vegetable extracts used in the manufacture of cosmetic products.

Every day the food industry uses more natural products such as spices, flavourings and food preservatives. Many aromatic and medicinal plants have antioxidant activity, germicidal and fungicidal actions which make them useful as food preservatives, attributed to volatile constituents such as phenols among other components. Precooked products gradually replace home cooked food and their preparation involves antioxidants, preservatives, flavourings and colourings of natural origin. This chapter describes the plants that are used in the manufacture of food preservatives, additives and supplements and those that are used for their organoleptic properties, such as spices and herbs.

Medicinal and aromatic plants play an important role in the pharmaceutical sector, both in the phytotherapy aspect, as in the strictly medicinal significance. Aromatherapy is the use of essential oils for therapeutic purposes. The absorption can be topical, oral or by inhalation. The second group includes all preventive and therapeutic use of MAP or their active ingredients. Active principles from medicinal plants are called phytopharmaceuticals, phytomedicines, herbal medicines or botanicals. Current pharmacopoeia reached more than 7,000 compounds derived from these plants. The uses of these substances include: 1) health care using natural products; 2) The newer drugs against the challenges of the twenty-first century (cancer, cholesterol, diabetes, dementia, depression, malaria, stress, etc.); 3) Essential oils used in aromatherapy; and 4) compounds useful in the veterinary area. The main species used in each of the previous four sections are introduced in this chapter.

Aromatic and medicinal plants are not only used in the pharmaceutical, cosmetic and food processing industries, as we have seen, but they have many other uses, increasing in number every day as new uses are researched and discovered. These other uses of MAPs are very important due to their growing economic importance and market possibilities. Natural dyes, pesticides, fungicides and insecticides, gums, resins, turpentines, allelopathic substances and tannins are some of them. Plant extracts have been used as insecticides since before ancient Rome, a practice that continues today with more than 2,000 species. There are different strategies and the compounds, such as allopathic substances, can be found in plants of different species. Resins, tannins, gums and balsams have been widely used until today and new products are still based on their natural properties.

The therapeutic activity of a plant medicine is determined by its quality, security and efficacy. These must be controlled in an exact, precise and repeatable process. Quality control is the set of technical operations employed to verify the fulfilment of the quality requirements established. The variability of the plant material depends on the identity of the plant, its origin (wild harvested or cultivated), the harvesting time, the soil and climatic conditions, the organ or part of the plant used, and the phenology and ontogeny of the plant. The plant or drug quality must be determined by identification of the plant material, botanically, physically and chemically.

Sustainable agriculture is based in the conservation of environmental and productive resources considering the socio-economical dimensions. The cultivation, production and collection of medicinal and aromatic plants (MAPs) are made up by a sector of the agriculture that should follow the concepts of sustainability. Our team researches in the area of sustainability, having developed agro-ecosystems and agroindustry valuation models. The objective was to develop evaluation tools with particular objectives: 1- an assessment model of lemon cultivation sustainability; 2- assessment tools in MAPs greenhouses and agro-industry; 3- introduction of principles for sustainable collection of wild species. Methodologies used by international organizations, like the UN or OECD, and specific models like FESLM (FAO) were taken as a reference. We worked with the construction of a Minimum Sustainable Set of Indicators (MSI) for each case. Sustainable assessment model for lemon cultivation were obtained. MSI for greenhouse’s MAPs cultivation and lemon and blueberries packing houses were developed. International principles for sustainable wild collection of MAPs were introduced. Considering the selected indicators, the results obtained are of those analysed systems that should check over and adjust their process, objectives and policies in the search of an improvement tendency towards sustainability. The harvest of wild species should start its way towards sustainability through the approach in the uses of standards.

This chapter presents the results of studies carried out in Argentina that assessed people’s willingness to pay (WTP) and willingness to accept (WTA) for useful plants conservation using the Contingent Valuation Methodology (CVM) and Avoided Costs Method (ACM). The WTP of residents in rural areas in Santiago del Estero, Argentina was researched. In this study residents expressed that medicinal, aromatic and dye plants are very important to them. In different parts of the province of Santiago del Estero, 125 families in six small towns were surveyed obtaining values of Consumer Surplus (CS) of $19.67 and Variation Compensatory (VC) of $22.156 (at an exchange rate US $1 equivalent to $3.20). Regarding dye plants, 35 artisans in these communities were also surveyed using the same method, and they expressed a willingness to pay (WTP) equivalent to $555.29 per month to preserve such plants. This tradition has been passed down over many generations, which ensures the availability of a continuous flow of environmental services. The results expressed in monetary terms that show the importance that environmental services provided by native forests for rural communities.

Wormwood (Artemisia absinthium L.) is a perennial plant known for its antifungal, parasitic and nematicidal effects. Its essential oil is rich in thujone which limits its industrial use due to neurotoxic effects. With the aim of domesticating plants free of thujone without sacrificing essential oil levels for use as a potential biopesticide, the study was conducted during 8 growing seasons at an experimental field located in Ejea de los Caballeros, Aragón, Spain. It compared two populations: the original population of wild plants collected in the Sierra Nevada National Park (Gr-75) and the selected population from a pre-trial in Teruel (Te-68). The trial was arranged according to a randomized block design with 3 replications. The experimental plot consisted of 6 rows of plants 20 meters long with 738 plants per population. Plants were harvested every year except for year one. The following variables were evaluated: production (in kilograms of fresh and dry biomass), essential oil obtained from steam-distilled biomass (l/ha) and plant mortality. All variables were checked annually. According to yearly averages, the Teruel population maintained a stable percentage of dry material with higher production of essential oil compared to the Granada population (39 l/ha on average). It was also apparent that essential oil production has a significant direct correlation with dry material. The result of the study is the ®Candial variety registered under Decision No EU 36714 of 27 January 2014 at the Community Plant Varieties Office.

Two thujone free Spanish populations of Artemisia absinthium from Teruel and Sierra Nevada (Spain) were submitted to a domestication process. The domestication resulted in lower chemical variation and higher biomass and essential oil yields, allowing for the registry of a new domesticated variety (® Candial). The main components of the new variety essential oil extracts were cis-epoxyocimene, chrysanthenol, chrysanthenyl acetate, trans-caryophyllene and linalool. The presence of 1.8-cineol and camphor correlated with the domestication level of A. absinthium. CO2 supercritical fluid extraction, improved the yield of (Z)-epoxyocimene, chrysanthenol, (5Z)-2,6-dimethylocta-5,7-diene-2,3-diol and trans-chrysanthenyl acetate. The development of extraction processes with supercritical CO2 allowed for the enrichment of desired bioactive compounds in A. absinthium extracts. The superctitical extracts showed strong antifeedant and insecticidal effects against Spodoptera littoralis, indicating that for insect control purposes supercritical CO2 extraction should be used. The semi-industrial vapor-pressure extracts (VPs) showed strong antifungal effects. (-)-cis-chrysanthenol has been identified as the chemical indicator of the antifungal quality of VP extracts from A. absinthium (® Candial). These VP extracts also showed a high nematocidal activity against animal parasitic nematode Trichinella spiralis without being cytotoxic to macrophage cells. These oils showed activity on the protozoan parasites Trypanosoma cruzi and Trichomonas vaginalis. The antiprotozoal activity of the VP oil was related with the presence of trans-caryophyllene and dihydrochamazulene. EOs from cultivated A. absinthium could be considered as potential candidates for development of new antifungal and insect antifeedant agents, as well as drugs against helminth and protozoan parasites.