No abstract

The aim of this work is to develop a new generation of repellent products with a long-lasting protection based on a natural component, para-menthane-3,8-diol (PMD). The active is first rendered soluble in a surfactantless microemulsion (H(2)O/(i)PrOH/PMD) and then in classical microemulsions. The presence of self-associated nanostructures is detected by dynamic light scattering (DLS). A synergetic system of surfactants (Cremophor) RH40 and Texapon N70) is used. Additionally, 2-ethylhexane-1,3-diol and ethyl (-)-(S)-lactate are incorporated. The final product contains, as main components, 46% of H(2)O, 25% of (i)PrOH, 20% of non-H(2)O-soluble PMD, and only 4% of surfactants. Investigations of lasting protection on human volunteers are carried out using a cage test bioassay protocol and Aedes aegypti mosquitoes. A complete protection of 315 min is found on the test persons using the surfactantless microemulsion. An extension is observed with the final formulation to reach a mean of complete protection of 385 min. This study demonstrates that alternative formulations using a natural active instead of synthetic chemicals like N,N-diethyl-m-methylbenzamide (DEET) can be efficient for human protection against mosquitoes.

In order to reduce the risk of getting infected with any epidemic disease transmitted by mosquitoes, repellent products are often used to protect populations at risk. The repellent potential of 19 essential oils from the island of Corsica, France, was evaluated in a bio-assay with the mosquito Aedes aegypti, in order to assess the 'space repellent' properties of these oils. Lavendula stoechas, Helichrysum italicum (leaves) and Laurus nobilis oils showed a capability of reducing the attractivity of a human finger for yellow fever mosquitoes in a Y-tube olfactometer. In addition to the behavioural studies on mosquitoes, two tests on the olfactory perception of these 19 oils were performed, involving 25 female and 25 male human volunteers. The aspects studied were the 'hedonic dimension' of these oils and their acceptance as a final fragrance for a repellent formulation. The experiments yielded promising results concerning both aspects for three oils, from Calamintha nepeta, Laurus nobilis and Rosmarinus officinalis, with minor differences between male and female participants. Laurus nobilis oil was the only oil tested fulfilling both properties: a spatial repellent effect on Aedes aegypti and acceptance by the volunteers for its integration in a repellent product. Thermogravimetric analysis showed that Calamintha nepeta oil has a slower evaporation rate in comparison to the Laurus nobilis and Rosmarinus officinalis oils.

A new set of beta-amino acids that carry various crown ether receptors on their side chains of the general formula (S)-beta(3)-HDOPA(crown ether) (HDOPA: homo-3,4-dihydroxyphenylalanine; (crown ether): [15]crown-5 ([15-C-5]), [18]crown-6 ([18-C-6]), [21]crown-7 ([21-C-7]), 1,2-Benzo-[24]crown-8 ([Benzo-24-C-8]) and (R)-Binol-[20]crown-6 ([(R)-Binol-20-C-6])) was prepared. Peptides that are based on these new crowned beta-amino acids combined with (1S,2S)-ACHC (2-aminocyclohexanecarboxylic acid), which is known to be a potent 3(14)-helix inducer, to the hexamer level, with two crowned residues at the i and i+3 positions of the main-chain, were synthesized in solution by stepwise coupling using Boc-N(alpha)-protection (Boc: tert-butoxycarbonyl) and the EDC/HOAt C-activation method. Their conformational analysis was performed by using FTIR absorption, NMR and CD spectroscopy techniques. Our results are in full agreement with a 3(14)-helix conformation.