Influence of Sex Ratio and Density on the Comparative Repellency of IR3535® Against Caged Aedes, Anopheles, and Culex Mosquitoes.

Studies on topical repellent efficacy conducted with caged mosquitoes in the laboratory are important to both the development and regulation of insect repellents. Guidelines for laboratory studies stipulate specific densities, sex ratios, and biting rates, whereas those for field studies are governmentally required before a promising repellent can be registered for human use. These protocols stipulate minimum biting rates alone. Relatively little is known, however, about the influence of mosquito density and sex ratio on their biting propensity, either in the field or laboratory. Using Environmental Protection Agency guidelines for cage testing, we studied the influence of mosquito density and sex ratio in laboratory repellency tests of the biopesticide Ethyl butylacetylaminopropionate (IR3535™) (20%) against three mosquito species (Aedes aegypti, Anopheles aquasalis, and Culex quinquefasciatus). DEET [3-(N-acetyl-N-butyl) aminopropionic acid ethyl ester] (20%) in a laboratory prepared formulation was used as a comparison article. Studies were conducted by trained investigators at the BioAgri Laboratories in Brazil. We found that higher mosquito density generally decreased protection time, but that the influence of sex ratio was more complex. The presence of male mosquitoes increased protection times against Aedes and Anopheles perhaps because mate-seeking males interfered with female feeding. Interestingly, by contrast, protection times decreased against Culex in the presence of males. Such considerations may potentially assist in improving the match between cage and field testing under a broader range of conditions that permit more accurate labeling of repellents for safe and effective use by consumers.

Sebusuppressive efficacy of the antioxidant bis-ethylhexyl hydroxydimethoxy benzylmalonate in the treatment of oily and blemished skin.

The aim of this study was to assess the effect of 2% bis-ethylhexyl hydroxydimethoxy benzylmalonate (HDBM; RonaCare(®) AP) as an active ingredient in the treatment of oily and blemished skin. This study was carried out as a randomized, placebo-controlled, single-blind study on 44 test subjects with blemished skin over a period of 8 weeks. Sebum measurement, skin inflammation/redness scoring by an expert, photographic documentation and a self-assessment with regard to skin improvement, and tests of skin compatibility and galenic characteristics were performed. Treatment with 2% HDBM resulted in a significant reduction of sebum excretion and showed efficacy against inflamed/red lesions also shown by photographic documentation. Efficacy and galenic performance of 2% HDBM were judged to be superior to the placebo emulsion. Additionally, 2% HDBM was well tolerated; approximately 80% of the test subjects rated the compatibility as good to very good.

The multifunctional role of ectoine as a natural cell protectant.

The protective properties of ectoine, formerly described for only extremophilic microorganisms, can be transferred to human skin. Our present data show that the compatible solute ectoine protects the cellular membrane from damage caused by surfactants. Transepidermal water loss measurements in vivo suggest that the barrier function of the skin is strengthened after the topical application of an oil in water emulsion containing ectoine. Ectoine functions as a superior moisturizer with long-term efficacy. These findings indicating that ectoine is a strong water structure-forming solute are explained in silico by means of molecular dynamic simulations. Spherical clusters containing (1) water, (2) water with ectoine, and (3) water with glycerol are created as model systems. The stronger the water-binding activity of the solute, the greater the quantity of water molecules remaining in the cluster at high temperatures. Water clusters around ectoine molecules remain stable for a long period of time, whereas mixtures of water and glycerol break down and water molecules diffuse out of the spheres. On the basis of these findings, we suggest that the hydrogen bond properties of solutes are not solely responsible for maintaining the water structure form. Moreover, the particular electrostatic potential of ectoine as an amphoteric molecule with zwitterionic character is the major cause for its strong affinity to water. Because of its outstanding water-binding activity, ectoine might be especially useful in preventing water loss in dry atopic skin and in recovering skin viability and preventing skin aging.