Biological effects of essential oils – A review

F. Bakkalia, b, S. Averbecka, D. Averbecka, Corresponding Author Contact Information, E-mail The Corresponding Author and M. Idaomarb

aInstitut Curie-Section de Recherche, UMR2027 CNRS/IC, LCR V28 CEA, Bât. 110, Centre Universitaire, 91405 Orsay cedex, France

bUniversité Abdelmalek Essâadi, Faculté des Sciences, Laboratoire de Biologie et Santé, BP 2121, Tétouan, Morocco


Abstract

Since the middle ages, essential oils have been widely used for bactericidal, virucidal, fungicidal, antiparasitical, insecticidal, medicinal and cosmetic applications, especially nowadays in pharmaceutical, sanitary, cosmetic, agricultural and food industries. Because of the mode of extraction, mostly by distillation from aromatic plants, they contain a variety of volatile molecules such as terpenes and terpenoids, phenol-derived aromatic components and aliphatic components. In vitro physicochemical assays characterise most of them as antioxidants. However, recent work shows that in eukaryotic cells, essential oils can act as prooxidants affecting inner cell membranes and organelles such as mitochondria. Depending on type and concentration, they exhibit cytotoxic effects on living cells but are usually non-genotoxic. In some cases, changes in intracellular redox potential and mitochondrial dysfunction induced by essential oils can be associated with their capacity to exert antigenotoxic effects. These findings suggest that, at least in part, the encountered beneficial effects of essential oils are due to prooxidant effects on the cellular level.

Keywords: Essential oil; Cytotoxicity; Genotoxicity; Antigenotoxicity; Prooxidant activity

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Acidification, heavy metal mobility and nutrient accumulation in the soil–plant system of a revegetated acid mine wasteland

Sheng-Xiang Yang, Bin Liao, Jin-tian Li, Tao Guo, Wen-Sheng Shu *

School of Life Sciences and State Key Laboratory of Biocontrol, Sun Yat-sen University, Guangzhou 510275, PR China

a b s t r a c t

A revegetation program was established at an extreme acidic and metal-toxic pyrite/copper mine wasteland in Guangdong Province, PR China using a combination of four native grass species and one nonnative woody species. It was continued and monitored for 2 y. The emphasis was on acidification, metal mobility and nutrient accumulation in the soil–plant system. Our results showed the following: (i) the acid-forming potential of the mine soils decreased steadily with time, which might be due to plant root-induced changes inhibiting the oxidization of sulphide minerals; (ii) heavy metal extractability (diethylene-triamine-pentaacetic acid-extractable Pb and Zn) in the soils increased with time despite an increase in soil pH, which might be attributed to soil disturbance and plant rhizospheric processes, as well as a consequence of the enhanced metal accumulation in plants over time; and (iii) the vegetation cover increased rapidly with time, and plant development accelerated the accumulation of major nutrients (organic matter, total and ammonium-N, and available P and K). The 2-y field experiment demonstrates that direct seeding/planting of native plant species in combination with lime and manure amelioration is a practical approach to the initial establishment of a self-sustaining vegetation cover on this metalliferous and sulphide-bearing mine wasteland. However, heavy metal accumulation in the soil–plant system should be of great concern, and long-term monitoring of ecological risk must be an integral part of such a restoration scheme.

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Promoting the promoter

Vincent Vedel^{, a, ,} and Ivan Scotti^a

^a UMR ECOFOG, INRA, Ecological genetic, Campus Agronomique de Kourou, BP 709, 97387 Kourou, French Guiana

Received 1 May 2010;

revised 23 September 2010;

accepted 27 September 2010.

Available online 2 October 2010.

Abstract

Recent evolutionary studies clearly indicate that evolution is mainly driven by changes in the complex mechanisms of gene regulation and not solely by polymorphism in protein-encoding genes themselves. After a short description of the cis-regulatory mechanism, we intend in this review to argue that by applying newly available technologies and by merging research areas such as evolutionary and developmental biology, population genetics, ecology and molecular cell biology it is now possible to study evolution in an integrative way. We contend that, by analysing the effects of promoter sequence variation on phenotypic diversity in natural populations, we will soon be able to break the barrier between the study of extant genetic variability and the study of major developmental changes. This will lead to an integrative view of evolution at different scales. Because of their sessile nature and their continuous development, plants must permanently regulate their gene expression to react to their environment, and can, therefore, be considered as a remarkable model for these types of studies.

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Heavy metal hyperaccumulating plants: How and why do they do it? And what makes them so interesting?

Nicoletta Rascio^{a, ,} and Flavia Navari-Izzo^b

^a Department of Biology, University of Padova, via U. Bassi 58/B, I-35121 Padova, Italy

^b Department of Chemistry and Agricultural Biotechnologies, University of Pisa, via San Michele degli Scalzi 2, I-56124 Pisa, Italy

Received 26 May 2010;

revised 25 August 2010;

accepted 26 August 2010.

Available online 15 September 2010.

Abstract

The term “hyperaccumulator” describes a number of plants that belong to distantly related families, but share the ability to grow on metalliferous soils and to accumulate extraordinarily high amounts of heavy metals in the aerial organs, far in excess of the levels found in the majority of species, without suffering phytotoxic effects. Three basic hallmarks distinguish hyperaccumulators from related non-hyperaccumulating taxa: a strongly enhanced rate of heavy metal uptake, a faster root-to-shoot translocation and a greater ability to detoxify and sequester heavy metals in leaves. An interesting breakthrough that has emerged from comparative physiological and molecular analyses of hyperaccumulators and related non-hyperaccumulators is that most key steps of hyperaccumulation rely on different regulation and expression of genes found in both kinds of plants. In particular, a determinant role in driving the uptake, translocation to leaves and, finally, sequestration in vacuoles or cell walls of great amounts of heavy metals, is played in hyperaccumulators by constitutive overexpression of genes encoding transmembrane transporters, such as members of ZIP, HMA, MATE, YSL and MTP families. Among the hypotheses proposed to explain the function of hyperaccumulation, most evidence has supported the “elemental defence” hypothesis, which states that plants hyperaccumulate heavy metals as a defence mechanism against natural enemies, such as herbivores. According to the more recent hypothesis of “joint effects”, heavy metals can operate in concert with organic defensive compounds leading to enhanced plant defence overall.

Heavy metal contaminated soils pose an increasing problem to human and animal health. Using plants that hyperaccumulate specific metals in cleanup efforts appeared over the last 20 years. Metal accumulating species can be used for phytoremediation (removal of contaminant from soils) or phytomining (growing plants to harvest the metals). In addition, as many of the metals that can be hyperaccumulated are also essential nutrients, food fortification and phytoremediation might be considered two sides of the same coin. An overview of literature discussing the phytoremediation capacity of hyperaccumulators to clean up soils contaminated with heavy metals and the possibility of using these plants in phytomining is presented.

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Exploring multiple drug and herbicide resistance in plants—Spotlight on transporter proteins

Sarah S. Conte and Alan M. Lloyd

^a University of Massachusetts Amherst, United States ^b University of Texas at Austin, United States

Abstract

Multiple drug resistance (MDR) has been extensively studied in bacteria, yeast, and mammalian cells due to the great clinical significance of this problem. MDR is not well studied in plant systems, although plant genomes contain large numbers of genes encoding putative MDR transporters (MDRTs). Biochemical pathways in the chloroplast are the targets of many herbicides and antibiotics, yet very little data is available regarding mechanisms of drug transport across the chloroplast membrane. MDRTs typically have broad substrate specificities, and may transport essential compounds and metabolites in addition to toxins. Indeed, plant transporters belonging to MDR families have also been implicated in the transport of a wide variety of compounds including auxins, flavonoids, glutathione conjugates, metal chelators, herbicides and antibiotics, although definitive evidence that a single transporter is capable of moving both toxins and metabolites has not yet been provided. Current understanding of plant MDR can be expanded via the characterization of candidate genes, especially MDRTs predicted to localize to the chloroplast, and also via traditional forward genetic approaches. Novel plant MDRTs have the potential to become endogenous selectable markers, aid in phytoremediation strategies, and help us to understand how plants have evolved to cope with toxins in their environment.

Research highlights

Multiple drug resistance (MDR) is not well studied in plant systems. The chloroplast is the target for many drugs and herbicides. The role of chloroplast transport proteins in MDR should be explored further. Novel plant MDRTs have the potential to become endogenous selectable markers, aid in phytoremediation strategies, and help us to understand how plants have evolved to cope with toxins in their environment.

Keywords: Multiple drug resistance (MDR); Herbicide resistance; Antibiotic resistance; Transport; Chloroplast

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