Exploring essential oils of Slovak medicinal plants for insecticidal activity: The case of Thymus alternans and Teucrium montanum subsp. jailae

Screening of Volatile Compounds, Traditional and Modern Phytotherapy Approaches of Selected Non-Aromatic Medicinal Plants (Lamiaceae, Lamioideae) from Rtanj Mountain, Eastern Serbia

Ironwort (Sideritis montana L.), mountain germander (Teucrium montanum L.), wall germander (Teucrium chamaedrys L.), and horehound (Marrubium peregrinum L.) are species widely distributed across Europe and are also found in North Africa and West Asia. Because of their wide distribution they express significant chemical diversity. For generations, these plants have been used as medical herbs for treating different aliments. The aim of this paper is to analyze volatile compounds of four selected species that belong to the subfamily Lamioideae, family Lamiaceae, and inspect scientifically proven biological activities and potential uses in modern phytotherapy in relation to traditional medicine. Therefore, in this research, we analyze the volatile compounds from this plants, obtained in laboratory by a Clevenger-type apparatus, followed by liquid-liquid extraction with hexane as the solvent. The identification of volatile compounds is conducted by GC-FID and GC-MS. Although these plants are poor in essential oil, the most abundant class of volatile components are mainly sesquiterpenes: germacrene D (22.6%) in ironwort, 7-epi-trans-sesquisabinene hydrate (15.8%) in mountain germander, germacrene D (31.8%) and trans-caryophyllene (19.7%) in wall germander, and trans-caryophyllene (32.4%) and trans-thujone (25.1%) in horehound. Furthermore, many studies show that, in addition to the essential oil, these plants contain phenols, flavonoids, diterpenes and diterpenoids, iridoids and their glycosides, coumarins, terpenes, and sterols, among other active compounds, which affect biological activities. The other goal of this study is to review the literature that describes the traditional use of these plants in folk medicine in regions where they grow spontaneously and compare them with scientifically confirmed activities. Therefore, a bibliographic search is conducted on Science Direct, PubMed, and Google Scholar to gather information related to the topic and recommend potential applications in modern phytotherapy. In conclusion, we can say that selected plants could be used as natural agents for promoting health, as a source of raw material in the food industry, and as supplements, as well as in the pharmaceutical industry for developing plant-based remedies for prevention and treatment of many diseases, especially cancer.

Ethanol and glycerol green emulsifying solvent for the formation of a Lavandula stoechas essential oil/β-cyclodextrin inclusion complex: mixture design and adulticidal activity against Culex pipiens

The purpose of this study is to investigate the effect of essential oil medium on the inclusion complex of L. stoechas EO in β-cyclodextrin, as well as to examine the impact of the encapsulating action on the adulticidal activity. In line with this, L. stoechas EO was hydrodistilled and determined through GC-MS. Furthermore, the optimization of EO medium was conducted using a binary mixture design of ethanol and glycerol as green emulsifier solvent. Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray powder diffraction and thermogravimetric analysis were used to verify the establishment of the IC. The insecticidal effect of the created formulation was evaluated against C. pipiens female mosquitoes. The optimum ethanol: glycerol ratio was 0.73: 0.27, corresponding to 58.86% of encapsulation efficiency. The fumigant test showed that, after 24 h of exposure, L. stoechas EO exerted only 24.56 ± 1.04%, while the encapsulated oil killed 57.89% of the adult population. At the highest dose (312.5 μl/L), the encapsulated oil provided the most significant effect on adults (100% mortality after 54 h) compared to non-encapsulated oil (100% mortality after 72 h). The encapsulated form of L. stoechas EO constitutes a promising alternative for the control of mosquitoes that are responsible for human diseases.

When Scent Becomes a Weapon—Plant Essential Oils as Potent Bioinsecticides

Crop protection still mostly relies on synthetic pesticides for crop pest control. However, the rationale for their continued use is shaded by the revealed adverse effects, such as relatively long environmental persistence that leads to water and soil contamination and retention of residues in food that brings high risks to human and animal health. As part of integrated pest management, biopesticides may provide crop protection, being eco-friendly and safe for humans and non-target organisms. Essential oils, complex mixtures of low-molecular-weight, highly volatile compounds, have been highlighted as major candidates for plant-derived bioinsecticides that are up to the sustainable biological standard. In this review, we screened the insecticidal activity of essential oils or their purified compounds, with focus given to their modes of action, along with the analyzed advantages and problems associated with their wider usage as plant-derived insecticides in agriculture.

A Review of the Phytochemistry, Traditional Uses and Biological Activities of the Essential Oils of Genus Teucrium

The genus Teucrium is a large and polymorphic genus of the Lamiaceae family distributed in mild climate zones, particularly in the Mediterranean basin and Central Asia. Studies of nonvolatile constituents of Teucrium species showed that they are a rich source of neo-clerodane diterpenoids, considered as chemotaxonomic markers of the genus. In addition to the nonvolatile metabolites, there has been a large interest in the essential oils of this genus. In this review, a complete survey of the chemical composition and biological properties of the essential oils isolated from Teucrium taxa is provided. In traditional medicine, since ancient times, species of this genus have been widely implemented for their biological properties, including antimicrobial, anti-inflammatory, antispasmodic, insecticidal, anti-malaria, etc. Therefore, a complete review of all of the traditional uses of Teucrium taxa are also reported.

Selected Aspects Related to Medicinal and Aromatic Plants as Alternative Sources of Bioactive Compounds

Natural compounds obtained from different medicinal and aromatic plants have gained respect as alternative treatments to synthetic drugs, as well as raw materials for different applications (cosmetic, food and feed industries, environment protection, and many others). Based on a literature survey on dedicated databases, the aim of the present work is to be a critical discussion of aspects regarding classical extraction versus modern extraction techniques; possibilities to scale up (advantages and disadvantages of different extraction methods usually applied and the influence of extraction parameters); and different medicinal and aromatic plants' different applications (medical and industrial applications, as well as the potential use in nanotechnology). As nowadays, research studies are directed toward the development of modern, innovative applications of the medicinal and aromatic plants, aspects regarding future perspectives are also discussed.

Essential oil based controlled-release non-toxic evaporating tablet provides effective repellency against Musca domestica

Housefly, Musca (M) domestica L. (Diptera: Muscidae) is a pervasive insect that transmits a variety of pathogens to humans and livestock. Although numerous synthetic pesticides are available to combat houseflies, their ecological and toxicological concerns have led to the exploration of natural products as safer alternatives. The present work was designed to develop an essential oil based controlled-release evaporating tablet (EO-CRT) and investigate its repellency against M. domestica. This study assesses the toxicological impacts of the EO-CRT following its sub-chronic inhalation exposure. Briefly, repellent activity of fourteen essential oils viz. lemon grass, bergamot, mentha, basil, camphor, lavender, clove, patchouli, rosemary, cinnamon, eucalyptus, citronella, jasmine and wild turmeric against M. domestica were screened using the 'Y'-tube olfactometer. The synergistic activity of the best four oils, under preliminary screening, were further evaluated by double and triple blending. The best combination of three oils were finalized for optimization with 17-run, 3-factor, 3-level Box-Behnken design. This was then employed to construct polynomial models and predict the best optimized formulation EO-CRT. EO-CRT was characterized by Differential Scanning Calorimetry (DSC) and Gas Chromatography-Mass Spectroscopy (GC-MS). The efficacy of the EO-CRT against M. domestica was assessed by attraction and repellent assay. Chest X-ray, histopathology and scanning electron microscopy of the exposed lung was performed to study EO-CRT's sub-chronic toxicity on Wistar rats. The EO-CRT showed slow release up to a period of 10 days at room temperature, exhibited 100% repellency (%Error=1.237) against M. domestica and was found to possess all the characteristics of an ideal formulation. Sub-chronic toxicity study further revealed the non-toxic nature of the EO-CRT. Thus, our study provides an assurance that the formulated EO-CRT could be effective not only in repelling the nuisance pest, M. domestica, in human dwellings, but also in minimizing the mechanical transmission of pathogens by it.