2023-09-15 18:45:09
Vegetables have weapons to attack or expel potential aggressors. Many times these tools are in the chemical components that constitute them and that human beings have used, first in a “homemade” way and later through industrial products.
However, there remain many unknown or little-studied species that could be useful as sources of insecticides or repellents, and that are also more environmentally friendly than the synthetic products available on the market.
For twenty years, a team from the Chair of Organic Chemistry and the Multidisciplinary Institute of Plant Biology (IMBIV) of the Faculty of Exact, Physical and Natural Sciences (FCEFyN) of the National University of Córdoba (UNC) in Argentina has been studying the flora aromatic plant of the country and the applications that the essential oils extracted from it can have.
Julio Zygadlo, professor at the FCEFyN and senior researcher at the National Council for Scientific and Technical Research (CONICET) of Argentina, who has led this work from the beginning, says that although all the studies they carried out were carried out on a laboratory scale, they identified some native plants essential oils that could be used for different purposes.
In a review of the scientific literature published on the subject, Zygadlo and the research team detected that sixty essential oils from native plants would have a potential repellent or insecticidal effect. “In several cases, the bioactivity of the essential oils was comparable or even better than that shown by the synthetic insecticides that were used as positive controls. “This work highlights the enormous potential of essential oils to be included in repellent and insecticidal formulations,” state the authors of the review.
“We found species with positive properties, that is, they have repellent capacity, but it is necessary to evaluate whether they are not toxic to people or pets. However, essential oils have very important qualities: they are biodegradable and the doses that would be used would not be a factor in water and soil contamination,” Zygadlo explains to Argentina Investiga.
Researchers have confirmed that the essential oils that achieve the best results in the laboratory are:
-As domestic bioinsecticides: eucalyptus and aguaribay.
-As repellents for lice: an indigenous tree of the Yungas of Salta and Tucuman, the Myrcianthescisplatensis, known by locals as guayabo or lapachillo, and the Aloysia riojana, species endemic to the Argentine northwest and known as poleo.
-For the control of mosquito larvae: the essential oils of suico (Tagetesminuta) and anisillo (Tagetespusilla) showed high effectiveness.
-As repellents for the house fly: the one that showed the best results was the plant known as “false pepper tree” (Schinus molle).
-As a bioinsecticide in agriculture: to control the corn grain weevil, the essential oil that worked best was peperin.
The authors of the new study have cataloged sixty essential oils from native plants that have potential as insecticides, repellents and for pest control. These essential oils can be very useful for the agricultural industry and as lice killers or mosquito repellents for domestic use. (Photo: National University of Córdoba / Argentina Investiga)
Bioensayos
The team also conducted an experiment to test repellent components for mosquitoes, vectors of many diseases. To do this, the volunteers exposed their arm with protection and a sample of essential oil to the presence of the insects.
The bioassays showed that derivatives of pichanilla (Baccharisspartioides), rosemary (Rosmarinusofficinalis) and lemon verbena (Aloysiacitrodora) were the most efficient as repellents. This work was carried out by UNC professor-researchers Raquel Gleiser and Yanina Gillij.
Another important aspect that is studied is the antimicrobial activity of essential oils, both for veterinary use and for protection in stored foods. “In rural areas, many people cure infections in livestock and pets with infusions of aromatic plants,” says Julio Zygadlo.
What are the signs that indicate the possible uses of a plant’s essential oil? The key is its chemical structure. “The most important chemical components of essential oils to achieve these tasks are the phenol family, especially thymol, carvacrol and eugenol, which work very well as antimicrobials and antifungals,” says Zygadlo.
Four success stories
In recent years, scientists from IMBIV and the Chair of Organic Chemistry carried out different projects with successful applications of essential oils to solve agribusiness problems.
Oils for silobags:
One of the problems that agricultural production has with silobags are the insects that affect the harvest that is stored there. That is why they created a development where essential oils derived from pepperine are introduced into the plastic matrix of the bag, using a technique called supercritical fluids. The result is a bioactive plastic that would have the potential to repel the corn weevil. Although the study is on a laboratory scale, the technology already has a patent. Specialists in Chemical Engineering participated in this work, and it was led by Jimena Herrera, Raquel Martini, Laura Goñi and Nicolás Gañán.
A shield for cochineal:
Another development that is in the process of being patented consists of applying a component to the base of vine plants, as if it were a paint. It does not allow the ants to climb and move the mealybug. They use pepperine essential oils, which have a very effective compound called pulegone. UNC researchers Laura Peschiutta and Daniela Mancilla work along these lines.
“Smart” and natural packages:
This project, which is still taking its first steps, aims to use bioactive compounds (essential oils) in flour packets to attack a moth and a beetle known as the “flour beetle.” The technology could also be used in materials such as Tetrabrik boxes.
Against chicken crackers:
They carried out an assessment at a small chicken farm where a beetle was attacking the birds. This generated a pattern of stress, a delay in growth and affected production. The UNC team incorporated essential oils into the dose of the synthetic insecticide used and made it more effective. “It was possible to lower the dose of the synthetic product and improve the action at the same time. Production and pollution costs were reduced compared to synthetic products,” says Zygadlo.
Natural versus synthetic
Most of the products available on the market to repel or combat insects are generated in laboratories through synthesis and manipulation of chemical structures taken from oil samples and allow, among many other things, to produce flavoring molecules. This is the cheapest and easiest to develop. So why turn to natural products?
Zygadlo explains it like this: “The natural products produced by plants – in the particular case of our line of study, essential oils – are used as defense elements against phytopathogenic microorganisms and against herbivores. We seek to use these properties to take care of our food and protect ourselves without generating pollution in the environment. The emergence of essential oils along with the plants that produce them occurred many millions of years ago, which has allowed a natural decontamination system to be generated in the environment. This makes these molecules – among other physical-chemical and structural reasons – biodegradable in reasonably short periods.”
However, the researcher insists that great care must be taken with the use of natural products. “Among natural compounds there are many substances that are very toxic. The role of the State in controlling the use of natural products is very important,” highlights the researcher and adds: “Essential oils are very interesting as a basis for, for example, the development of biopesticides. Unlike other natural compounds, these already have an international market that provides raw materials. However, there are other natural products that require prior steps of domestication of the producing plants and development or adaptation of extractive techniques, which entails investment costs that often discourage the use of these compounds.” (Source: Argentina Investiga / Lucas Gianre / National University of Córdoba)
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