Essential oils as potential bioactive compounds against mosquitoes

GLEISER, R.M.; ZYGADLO, J.A.

Recent Advances in Phytochemistry

Research Signpost

Lugar: Kerala; Año: 2009; p. 53 - 76

Mosquitoes are insects of medical, veterinary and economical importance. The current global strategy for the control of vector-borne diseases is based on vector control, with chemical control as a main component of integrated vector management. The development of resistance to insecticides, and environmental concerns among other factors has led to the search of alternative products, such as plant products that may be biodegradable to non-toxic compounds. The properties of essential oils (EO) as larvicides, adulticides, ovicides/ oviposition deterrents and repellents is reviewed. Formulations including bases or fixative materials improve repellency of EOs that are effective but for relatively short periods due to their volatility. Several oils, their components or combination of components are promising as insecticides, however, variations in toxicity of the EO against different mosquito species are common. Also, synergisms and antagonisms between EO components have been reported. Thus, further research on their mode of action is needed to identify key constituents with universal properties and for the development of efficient formulations. This book follows two other review books in the field of Phytochemistry published (both by Research Signpost) in 2003 (“Advances in Phytochemistry”) and in 2006 (“Phytochemistry: Adavances in Research”). Chapter 1 deals with critical mechanisms by which the activity of toxic xenobiotics of natural origin is biochemically manifested according to recent advances in the subject. Toxic compounds are produced by a vaste number of species but little is known about molecular mechanisms of toxicity of these compounds. For example, the intimate physicochemical mechanism that could explain toxicity of poison hemlock (Conium maculatum), a plant known since ancient times, remain unknown to this day. Chapter 2 deals with essential oils (EO) as potential bioactive compounds against mosquitos. The development of resistance to chemical insecticides and environmental impact of most synthetic products have led to search of alternative products such as plant metabolites that may be degradable to non toxic products. Properties of EO as larvicides, adulticides, ovicides, oviposition deterrents and repellents are reviewed. Several EO, their constituents or combination of constituents are promising insecticides. Variations in toxicity of EO against different mosquito species are common; in addition synergism and antagonism between constituents of EO may alter their efficiency. Chapter 3 deals with mass spectrometry of fungal peptides. Fungal peptides have received increased interest in recent years because they have shown a variety of biological activities; these peptides contain non proteogenic amino acids (sometimes in high proportions) and can be linear or cyclic. Due to great variety of amino acids in these structures and to the complexity of samples, mass spectrometry (MS) has become an essential tool for structural elucidation of these peptides. Mass spectrometric techniques currently employed for the analysis of fungal peptides are described. Analysis of positive monocharded ions, positive multicharded ions, negative ions together with high energy collision induced dissociation and high accuracy MS are discussed. The successful application of MS and MS/ MS for structural elucidation of fungal peptides has been shown in a wide variety of compounds. Chapter 4 deals with phytochemistry and pharmacology of Geranium species. Distribution of flavonoid aglycones and distribution of flavonoid-O-glycosides in eleven species of the genus Geranium growing in Bulgaria are described together with hydrolysable tannins, condensed tannins and phenolic acids. In addition the review deals with constituents of essential oils from G. robertianum, G. macrorrhizum and G. phaeum. Antiviral, antimicrobial, antioxidant activities together with antiradiation, immunostimulatory, depressive and antileishmanial actions of extracts of Geranium species are described. Chapter 5 deals with history, botanic description, industrial processing, traditional uses, phytochemistry, pharmacological activities, indications, toxicity, side effects and contraindications of “mate” (Ilex paraguariensis St. Hil. (Aquifoliaceae)), a widely distributed tree or shrub native from Northeast Argentina, Southern Brazil, Paraguay and Uruguay. The dried and ground leaves of this plant are used as very popular folk beverage called “mate” dating from pre-Columbian times. Nowadays leaves and their extracts are also used in complementary and alternative medicine as central nervous system stimulant, diuretic, weight reducing, antioxidant and antihypercholeserolemic. Methyl xanthines, flavonoids, vitamins, caffeoyl quinic acids and saponins are constituents of “mate” together with more than 100 compounds detected in the volatile fractions. Chapter 6 deals with new plant flavonoids having cytotoxic activity isolated in recent years. Eight-tree such compounds (flavones, flavonols and their glycosides, chalcones, flavanones, flavans, isoflavonoids and biflavonoids) are described together with a number of known flavonoids having cytotoxic activity. In vitro studies show the anticancer activities of flavonoids in various cell lines.