http://naturalingredient.org/wp/wp-content/uploads/Burt_Essential_Oils_A_Review_2004.pdf

Essential oils: their antibacterial properties and potential applications in foods--a review.

For decades, studies of endocrine-disrupting chemicals (EDCs) have challenged traditional concepts in toxicology, in particular the dogma of “the dose makes the poison,” because EDCs can have effects at low doses that are not predicted by effects at higher doses. Here, we review two major concepts in EDC studies: low dose and nonmonotonicity. Low-dose effects were defined by the National Toxicology Program as those that occur in the range of human exposures or effects observed at doses below those used for traditional toxicological studies. We review the mechanistic data for low-dose effects and use a weight-of-evidence approach to analyze five examples from the EDC literature. Additionally, we explore nonmonotonic dose-response curves, defined as a nonlinear relationship between dose and effect where the slope of the curve changes sign somewhere within the range of doses examined. We provide a detailed discussion of the mechanisms responsible for generating these phenomena, plus hundreds of examples from...

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Hormones and endocrine-disrupting chemicals: Low-dose effects and nonmonotonic dose responses

LEARNING The objectives of BIOS 781 are to present: OBJECTIVES: 1. basic population and quantitative genetic principles, including classical genetics, chromosomal theory of inheritance, and meiotic recombination 2. an exposure to QTL mapping methods of complex quantitative traits and linkage methods to detect co-segregation with disease 3. methods for assessing marker-disease linkage disequilibrium, including case-control approaches 4. methods for genome-wide association and stratification control.

Genetic Data Analysis

Plants have a penchant for perfuming the atmosphere around them. Since antiquity it has been known that both floral and vegetative parts of many species emit substances with distinctive smells. The discovery of the gaseous hormone ethylene 70 years ago brought the realization that at least some of

/pdf/biochemistry-of-plant-volatiles-5959ugu5bg.pdf

Biochemistry of Plant Volatiles

Chitosan based edible films and coatings: A review

Peppermint (Mentha × piperita L.) was independently transformed with a homologous sense version of the 1-deoxy-d-xylulose-5-phosphate reductoisomerase cDNA and with a homologous antisense version of the menthofuran synthase cDNA, both driven by the CaMV 35S promoter. Two groups of transgenic plants were regenerated in the reductoisomerase experiments, one of which remained normal in appearance and development; another was deficient in chlorophyll production and grew slowly. Transgenic plants of normal appearance and growth habit expressed the reductoisomerase transgene strongly and constitutively, as determined by RNA blot analysis and direct enzyme assay, and these plants accumulated substantially more essential oil (about 50% yield increase) without change in monoterpene composition compared with wild-type. Chlorophyll-deficient plants did not afford detectable reductoisomerase mRNA or enzyme activity and yielded less essential oil than did wild-type plants, indicating cosuppression of the reductoisomerase gene. Plants transformed with the antisense version of the menthofuran synthase cDNA were normal in appearance but produced less than half of this undesirable monoterpene oil component than did wild-type mint grown under unstressed or stressed conditions. These experiments demonstrate that essential oil quantity and quality can be regulated by metabolic engineering. Thus, alteration of the committed step of the mevalonate-independent pathway for supply of terpenoid precursors improves flux through the pathway that leads to increased monoterpene production, and antisense manipulation of a selected downstream monoterpene biosynthetic step leads to improved oil composition.

https://www.pnas.org/content/pnas/98/15/8915.full.pdf

Metabolic engineering of essential oil yield and composition in mint by altering expression of deoxyxylulose phosphate reductoisomerase and menthofuran synthase.

Strategies for transgenic manipulation of monoterpene biosynthesis in plants.

Lavenders and their essential oils have been used in alternative medicine for several centuries. The volatile compounds that comprise lavender essential oils, including linalool and linalyl acetate, have demonstrative therapeutic properties, and the relative abundance of these metabolites is greatly influenced by the genetics and environment of the developing plants. With the rapid progress of molecular biology and the genomic sciences, our understanding of essential oil biosynthesis has greatly improved over the past few decades. At the same time, there is a recent surge of interest in the use of natural remedies, including lavender essential oils, in alternative medicine and aromatherapy. This article provides a review of recent developments related to the biosynthesis and medicinal properties of lavender essential oils.

/pdf/biosynthesis-and-therapeutic-properties-of-lavandula-2n4qylg379.pdf

Biosynthesis and therapeutic properties of Lavandula essential oil constituents.

(+)-Pulegone is a central intermediate in the biosynthesis of (-)-menthol, the most significant component of peppermint essential oil. Depending on environmental conditions, this branch point metabolite may be reduced to (-)-menthone en route to menthol, by pulegone reductase (PR), or oxidized to (+)-menthofuran, by menthofuran synthase (MFS). To elucidate regulation of pulegone metabolism, we modified the expression of mfs under control of the CaMV 35S promoter in transformed peppermint plants. Overexpression and cosuppression of mfs resulted in the respective increase or decrease in the production of menthofuran, indicating that the control of MFS resides primarily at the level of transcription. Significantly, in both WT peppermint as well as in all transformed plants, the flux of (+)-pulegone through PR correlated negatively with the essential oil content of menthofuran, such that menthofuran, and pulegone increased, or decreased, in concert. These results suggested that menthofuran itself might influence the reduction of pulegone. Although (+)-menthofuran did not inhibit (+)-PR activity, stem feeding with menthofuran selectively decreased pr transcript levels in immature leaves, thereby accounting for decreased reductase activity and increased pulegone content. These data demonstrate that the metabolic fate of (+)-pulegone is controlled through transcriptional regulation of mfs and that menthofuran, either directly or indirectly, influences this process by down-regulating transcription from pr and/or decreasing pr message stability. The ability to reduce both menthofuran and pulegone levels is of commercial significance in improving essential oil quality; however, the physiological rationale for such complex regulation is presently unclear.

https://www.pnas.org/content/pnas/100/24/14481.full.pdf

Menthofuran regulates essential oil biosynthesis in peppermint by controlling a downstream monoterpene reductase

Peppermint (Mentha × piperita L.) was transformed with various gene constructs to evaluate the utility of metabolic engineering for improving essential oil yield and composition. Oil yield increases were achieved by overexpressing genes involved in the supply of precursors through the 2C-methyl-D-erythritol 4-phosphate (MEP) pathway. Two-gene combinations to enhance both oil yield and composition in a single transgenic line were assessed as well. The most promising results were obtained by transforming plants expressing an antisense version of (+)-menthofuran synthase, which is critical for adjusting the levels of specific undesirable oil constituents, with a construct for the overexpression of the MEP pathway gene 1-deoxy-D-xylulose 5-phosphate reductoisomerase (up to 61% oil yield increase over wild-type controls with low levels of the undesirable side-product (+)-menthofuran and its intermediate (+)-pulegone). Elite transgenic lines were advanced to multiyear field trials, which demonstrated consistent oil yield increases of up to 78% over wild-type controls and desirable effects on oil composition under commercial growth conditions. The transgenic expression of a gene encoding (+)-limonene synthase was used to accumulate elevated levels of (+)-limonene, which allows oil derived from transgenic plants to be recognized during the processing of commercial formulations containing peppermint oil. Our study illustrates the utility of metabolic engineering for the sustainable agricultural production of high quality essential oils at a competitive cost.

https://www.pnas.org/content/pnas/108/41/16944.full.pdf

Soheil S. Mahmoud

Papers

Metabolic engineering of essential oil yield and composition in mint by altering expression of deoxyxylulose phosphate reductoisomerase and menthofuran synthase.

Strategies for transgenic manipulation of monoterpene biosynthesis in plants.

Biosynthesis and therapeutic properties of Lavandula essential oil constituents.

Menthofuran regulates essential oil biosynthesis in peppermint by controlling a downstream monoterpene reductase

Improving peppermint essential oil yield and composition by metabolic engineering