"Gold" Pressed Essential Oil: An Essay on the Volatile Fragment from Citrus Juice Industry By-Products Chemistry and Bioactivity.

Present essay explores the potentials of Citrus juice industry's by-products as alternative bioactive natural products resources. Four crude Cold Pressed Essential Oils (CPEOs), derived from orange, lemon, grapefruit, and mandarin, were studied. All CPEOs were subjected to water distillation, in order to obtain the volatile fragment, which was further fractionated with respect to distillation period in two parts, concluding to eight samples. These samples along with the four original CPEOs were assessed in relation to their phytochemical content and their repellent and larvicidal properties against Asian Tiger Mosquito. The volatiles recovery rates ranged from 74% to 88% of the CPEO. Limonene presented a significant increase in all samples ranging from 8% to 52% of the respective CPEO's content and peaked in mandarin's 2nd volatile fragment which comprised 97% of the essential oil. The refinement process presented clear impacts on both bioassays: a significant increase in larvicidal potency was observed, annotated best by the improvement by 1100% and 1300% of the grapefruit volatile fractions; repellence testing provided only one significant result, the decrease of landings by 50% as a response to mandarin's second volatile fraction. The applied methodology thus may be considered for the improvement of Citrus juice industry's by-products chemistry and bioactivity.

Seasonal variation and bioactivity of the essential oils of two Juniperus species against Aedes (Stegomyia) albopictus (Skuse, 1894).

The seasonal variation in respect to the yield and chemical composition of 24 essential oils (EOs) isolated from various parts (leaves and fruits) of two indigenous Greece Juniperus species (family Cupressaceae), namely Juniperus drupacea and Juniperus phoenica, were determined by GC and GC/MS analysis. The larvicidal properties of these EOs were evaluated against 3rd and early 4th instar larvae of Aedes (Stegomyia) albopictus (Skuse, 1894) at one screening dose (29 mg L(-1)). Moreover, the repellent activity against adult mosquitoes was also evaluated at one screening dose. The analytical data indicated that the EOs mainly consisted of monoterpenes, mostly cyclic and only occasionally aliphatic and to a lesser percent diterpenes. The EOs yield was sharply increased when the plant material was subjected to pre-treatment before steam distillation. Finally, the influence of plant material collection period on their yield and chemical content was also determined. Bioactivity assessments indicated that three EOs possess very potent larvicidal properties and 12 EOs display significant repellent activities since they were proved to be "DEET-like." Therefore, they represent an inexpensive source of natural mixtures of larvicidal and repellent mixture of natural compounds, with potentials for application for utilization in mosquito control schemes in order to prevent the expansion of viral infections.

Essential oils of indigenous in Greece six Juniperus taxa: chemical composition and larvicidal activity against the West Nile virus vector Culex pipiens.

The chemical composition of 14 essential oils (EOs), obtained from various parts (leaves, fruits, wood) of the six indigenous in Greece Juniperus family taxa, was determined by GC and GC/MS analysis. The insecticidal properties of these EOs were evaluated against Culex pipiens L. larvae of 3rd and early 4th instars, in order to delineate the relationship between the phytochemical content of the EOs and their larvicidal activities. The analytical data indicated that the EOs mainly consisted of monoterpenes, mostly cyclic and only occasionally aliphatic, and to a lesser percent, of diterpenes. The larvicidal bioassays against C. pipiens larvae revealed that the most active EO was derived from the wood of Juniperus drupacea and contains mainly non-oxygenated monoterpenes and a significant amount of diterpenes, displaying the highest chemodiversity. Its initial LC(50) value was 26.47 mg L(-1). On the contrary, the EO isolated from J. phoenicea berries, which consisted of monoterpenes (non-oxygenated, cyclic), was the less active displaying an LC(50) value of 96.69 mg L(-1). In respect to the contained phytochemicals, myrcene was assayed as the most toxic, displaying an LC(50) value of 33.83 mg L(-1), while the four isomers of pinene abundant in all EOs were less active exhibiting LC(50) values ranging from 70.40 to 94.88 mg L(-1). Results herein reveal that the EOs isolated from the studied Juniperus family taxa represent an inexpensive source of natural mosquito control mixtures.

Chemical composition and larvicidal activity of essential oils from six Apiaceae family taxa against the West Nile virus vector Culex pipiens.

The chemical compositions of essential oils (EOs) obtained from six different taxa of the Apiaceae family, Apioideae subfamily, belonging to three tribes and six different genuses were determined by gas chromatography and gas chromatography-mass spectrometry analyses. All examined plants grow naturally in different habitats throughout Greece. The insecticidal properties of these EOs were evaluated against Culex pipiens L. larvae of third and early fourth instars in order to delineate the relationship between the EOs phytochemical content and larvicidal activity. The analytical data indicated that the EOs are mainly consisted of monoterpenes, mostly cyclic and only occasionally aliphatic. The larvicidal bioassay results indicated that the oil of Oenanthe pimpinelloides L., which contains mainly nonoxygenated monoterpenes, possesses the highest activity against Cx. pipiens larvae, displaying a LC(50) value of 40.26 mg/L. On the contrary, the EO of Elaeoselinum asclepium (L.) Bertol, which is consisted of pinenes and oxygenated monoterpenes, was the less active (LC(50) value of 96.96 mg/L). These results reveal that the nonoxygenated monoterpenes possess potent insecticidal activities against Cx. pipiens L. and the EO of O. pimpinelloides L. represents an inexpensive source of natural pest control mixture.

A newly developed assay to study the minimum inhibitory concentration of Satureja spinosa essential oil.

AIMS: The minimum inhibitory concentration (MIC) of Satureja spinosa essential oil against Staphylococcus aureus, Escherichia coli O157:H7, Listeria monocytogenes, Salmonella enterica, Salmonella serovar Enteritidis PT4 and Bacillus cereus was comparatively assessed with an established optical density method as well as a novel impedimetric method. METHODS AND RESULTS: The impedimetric analysis takes into account information of microbial growth, such as detection time, maximum conductance, and slope of the conductance curve. For each pathogen two levels of inoculation were studied, a high (10(5) CFU ml(-1)) and a low level (10(2) CFU ml(-1)). Non-linear regression analysis was used to fit the data using a modification of a previously published model, from which a more exact value can be obtained for the MIC. Both methods gave similar MICs as shown by t-test statistical analysis. Salm. Enteritidis seems to be the least sensitive to the action of S. spinosa essential oil followed by L. monocytogenes, E. coli, B.cereus and Staph. aureus. The MICs of low inoculum were lower than that of high inoculum. CONCLUSIONS: The new impedimetric assay of MIC of essential oils can be considered a reliable rapid method for screening antimicrobial effectiveness of natural additives. SIGNIFICANCE AND IMPACT OF THE STUDY: Determination of the minimum inhibitory concentration of an essential oil with the simple conductance technique and further study of the mode of action of its components is a good combination for obtaining additional knowledge for industrial application of such natural additives.