Seasonal variation in the chemical composition and larvicidal activity against Aedes aegypti L. of essential oils from Brazilian Amazon.

Arthropod-borne viral diseases are important public health threats in tropical countries. In the Americas, diseases such as Dengue, Zika, Chikungunya, Mayaro, and Yellow fever, which are mainly transmitted by Aedes aegypti L. are responsible for high rates of morbidity and mortality in the populations. The incidence of those viruses has increased in the last few years, due to the decrease of vector control programs, as well as, the resistance of this vector in front of many products that have been used in this proposal. Plant-based products such as essential oils are a promising alternative for Ae. aegypti control. In this context, the present work aims to investigate the seasonality effect on the larvicidal potential and safety of essential oils from 4 endemic plants of the Brazilian Amazon, as well as to verify their larvicidal activity and safety. The species were collected in the rainy and dry periods (Eugenia uniflora L., Lantana camara L., Ocimum basilicum L., Plectranthus neochilus Schlrt.). The essential oils were extracted by hydrodistillation and chemical composition was determined by gas chromatography coupled to mass spectrometry. The larvicidal activity was performed according to the methodology recommended by the World Health Organization. The safety of the oil use was evaluated against two non-target organisms: Artemia salina Leach and Danio rerio Hamilton Buchanan. Essential oils of E. uniflora, L. camara, O. basilicum, P. neochilus, presented as major compounds, in both collection periods, the substances Curzerene, Germacrene D, Methyl chavicol and, Caryophyllene, respectively. However, showed a qualitative and quantitative variation of this composition. All oils showed promising results against Ae. aegypti larvae with LC50 between 41.7 and 275.8 µg/mL. They were efficient against Ae. aegypti but showed high toxicity to non-target organisms, requiring additional safety studies. Despite these results showing that those essential oils are not ideal larvicides because they presented toxicity to non-target organisms, bioprospection is a promising tool to help reduce the dissemination of arboviruses, and they can use in artificial breeders of Ae. aegypti larvae, where water will not be reused for human consumption or have other cohabiting organisms.

Essential oils and their chemical constituents against Aedes aegypti L. (Diptera: Culicidae) larvae.

This review focused on the toxicity of essential oils and their constituents against Aedes aegypti L. (Diptera, Culicidae) larvae, a key vector of important arboviral diseases, such as dengue, chikungunya, zika, and yellow fever. This review is based on original articles obtained by searching major databases in the last six years. Our literature review shows that 337 essential oils from 225 plant species have been tested for larvicidal bioactivity. More than 60% of these essential oils were considered active (LC50<100 µg/mL). Most species belong to the families Lamiaceae (19.3%), Lauraceae (9.9%), and Myrtaceae (9.4%). The plants studied for their larvicidal activity against A. aegypti were mainly collected in India and Brazil (30 and 20%, respectively) and the parts of the plants most used were the leaves. Less than 10% of essential oils were evaluated for toxicity against non-target organisms and with the aim to demonstrate safe use. The most used plant parts are leaves and the main compounds of essential oils were described. The most active essential oils are rich in sesquiterpene hydrocarbons, oxygenated sesquiterpenes, and monoterpene hydrocarbons. Here, factors affecting bioactivity (chemical composition, plant parts, and harvesting site) of essential oils and their constituents, as well as safety to non-target organisms are discussed. Essential oils have considerable potential against A. aegypti. This review shows that essential oils might be used to control arboviruses, and further studies on safety and formulations for application in the field should be performed.

Chemical Profile and Biological Activities of Essential Oil from Artemisia vulgaris L. Cultivated in Brazil.

Essential oil from the leaves of Artemisia vulgaris L. (Compositae) cultivated in Brazil was investigated for its chemical composition and biological activities including antibacterial, antifungal, and anthelmintic. The constituents of essential oils isolated by hydro-distillation were examined by GC-MS and a total of 18 components were identified. The essential oil was dominated by oxygenated sesquiterpenes (44.4%), sesquiterpene hydrocarbons (33.3%), and oxygenated monoterpenes (16.6%). Caryophyllene (37.45%), germacrene D (16.17%), and humulene (13.66%) were the major components. The essential oils from A. vulgaris showed bactericidal and fungicidal properties against Staphylococcus aureus and Candida albicans, respectively. Anthelmintic activity against Haemonchus contortus was absent in this essential oil. Altogether above results indicate that essential oils from A. vulgaris can be used for various medicinal purposes.

Towards a better understanding of Artemisia vulgaris: Botany, phytochemistry, pharmacological and biotechnological potential.

Artemisia vulgaris is one of the important medicinal plant species of the genus Artemisia, which is usually known for its volatile oils. The genus Artemisia has become the subject of great interest due to its chemical and biological diversity as well as the discovery and isolation of promising anti-malarial drug artemisinin. A. vulgaris has a long history in treatment of human ailments by medicinal plants in various parts of the world. This medicinal plant possesses a broad spectrum of therapeutic properties including: anti-malarial, anti-inflammatory, anti-hypertensive, anti-oxidant, anti-tumoral, immunomodulatory, hepatoprotective, anti-spasmodic and anti-septic. These activities are mainly attributed to the presence of various classes of secondary metabolites, including flavonoids, sesquiterpene lactones, coumarins, acetylenes, phenolic acids, organic acids, mono- and sesquiterpenes. Studies related to A. vulgaris morphology, anatomy and phytochemistry has gained a significant interest for better understanding of production and accumulation of therapeutic compounds in this species. Recently, phytochemical and pharmacological investigations have corroborated the therapeutic potential of bioactive compounds of A. vulgaris. These findings provided further evidence for gaining deeper insight into the identification and isolation of novel compounds, which act as alternative sources of anti-malarial drugs in a cost-effective manner. Considering the rising demand and various medical applications of A. vulgaris, this review highlights the recent reports on the chemistry, biological activities and biotechnological interventions for controlled and continuous production of bioactive compounds from this plant species.

Biological properties and pharmacological potential of plant exudates.

Exudates released from plants, consist of complex mixtures of organic and inorganic molecules that have been used in traditional medicine from several years. They may vary among genera, species or within a genus and mainly include latex, sap, gums, resins, seed or root exudates. Plant exudates are known to possess several biological activities including, antimicrobial, anti-inflammatory, antioxidant, wound healing and anti-nociceptive. Exudates oozed out from plants have also been used as ingredients in medicines, food, perfumes and cosmetics. The present review provides brief overview about the exudates released from plants, their biological properties and beneficial effects for human beings. Due to the presence of various compounds, different methodologies and procedures have been employed for their collection and analyses. Literature studies suggest that plant exudates have extensive therapeutic potential for curing diseases with minimal toxic effects. This aspect could be taken into account in prospective studies regarding the search of new products derived from plant exudates with pharmaceutical value.

The Hydroalcoholic Extract Obtained from Mentha piperita L. Leaves Attenuates Oxidative Stress and Improves Survival in Lipopolysaccharide-Treated Macrophages.

Mentha piperita L. (peppermint) possesses antimicrobial properties, but little is known of its ability to modulate macrophages. Macrophages are essential in bacterial infection control due to their antimicrobial functions and ability to link the innate and adaptive immune responses. We evaluated the effects of the peppermint leaf hydroalcoholic extract (LHAE) on cultured murine peritoneal macrophages stimulated or not with lipopolysaccharide (LPS) in vitro. Vehicle-treated cells were used as controls. The constituents of the extract were also identified. Epicatechin was the major compound detected in the LHAE. LPS-induced macrophage death was reversed by incubation with LHAE (1-30 µg/ml). Higher concentrations of the extract (≥100 µg/ml) decreased macrophage viability (49-57%) in the absence of LPS. LHAE (1-300 µg/ml) attenuated H2O2 (34.6-53.4%) but not nitric oxide production by these cells. At similar concentrations, the extract increased the activity of superoxide dismutase (15.3-63.5-fold) and glutathione peroxidase (34.4-73.6-fold) in LPS-treated macrophages. Only LPS-unstimulated macrophages presented enhanced phagocytosis (3.6-6.6-fold increase) when incubated with LHAE (3-30 µg/ml). Overall, the LHAE obtained from peppermint modulates macrophage-mediated inflammatory responses, by stimulating the antioxidant pathway in these cells. These effects may be beneficial when the excessive activation of macrophages contributes to tissue damage during infectious disease.