A novel hydroxamic acid-containing antibiotic produced by a Saharan soil-living Streptomyces strain

During screening for potentially antimicrobial actinobacteria, a highly antagonistic strain, designated WAB9, was isolated from a Saharan soil of Algeria. A polyphasic approach characterized the strain taxonomically as a member of the genus Streptomyces. The strain WAB9 exhibited a broad spectrum of antimicrobial activity toward various multidrug-resistant micro-organisms. A PCR-based assay of genomic potential for producing bioactive metabolites revealed the presence of PKS-II gene. After 6 days of strain fermentation, one bioactive compound was extracted from the remaining aqueous phase and then purified by HPLC. The chemical structure of the compound was determined by spectroscopic (UV-visible, and (1)H and (13)C NMR) and spectrometric analysis. The compound was identified to be 2-amino-N-(2-amino-3-phenylpropanoyl)-N-hydroxy-3-phenylpropanamide, a novel hydroxamic acid-containing molecule. The pure molecule showed appreciable minimum inhibitory concentration values against a selection of drug-resistant bacteria, filamentous fungi and yeasts. Significance and impact of the study: This study presents the isolation of a Streptomyces strain, named WAB9, from a Saharan soil in Algeria. This strain was found to produce a new hydroxamic acid-containing molecule with interesting antimicrobial activities towards various multidrug-resistant micro-organisms. Although hydroxamic acid-containing molecules are known to exhibit low toxicities in general, only real evaluations of the toxicity levels could decide on the applications for which this new molecule is potentially most appropriate. Thus, this article provides a new framework of research.

Improved synthesis of hyaluronic acid hydrogel and its effect on tissue augmentation

HA-HMDA hydrogels were developed by direct amide bond formation between the carboxyl groups of hyaluronic acid (HA) and hexamethylenediamine (HMDA) with an optimized carboxyl group modification in the preliminary experiment. However, these HA-HMDA hydrogels transformed into an unstable liquid form after steam sterilization, and were problematic for application to actual dermal filler. A new method to overcome the problem of the previously developed HA-HMDA hydrogels is to prepare them by adjusting the pH in this study. Not only are these improved HA-HMDA hydrogels prepared with lower amounts of cross-linking and activation agents compared to the previously developed hydrogels, but they also maintain a stable form after steam sterilization. These improved HA-HMDA hydrogels showed higher viscoelasticity and longer lasting effects than the previous ones, despite the fact that the amount of the HMDA used as a cross-linking agent as well as 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide (EDC) and 1-hydroxybenzotriazole monohydrated (HOBt) used as activation agents were substantially reduced. According to an in vivo test using a wrinkled mouse model, the improved HA-HMDA hydrogels exhibited significantly improved tissue augmentation effects compared to a positive control of Restylane, which is widely used for the tissue augmentation throughout the world. Furthermore, histological analysis revealed excellent biocompatibility and safety of the improved synthesized HA-HMDA hydrogels.

Inhibitory effect of N-adamantyl-3,4-dihydroxybenzamide on melanogenesis in melan-a cells and brown guinea pigs

To find novel depigmenting agents, a new synthetic compound, N-adamantyl-3,4-dihydroxybenzamide (NADB) was produced and the effects on melanogenesis were investigated. Our results showed that NADB reduced melanin synthesis in a dose-dependent manner in melan-a cells. Tyrosinase activity was also reduced by NADB treatment in melan-a cells. However, NADB did not inhibit tyrosinase activity directly in a cell-free system. Treatment of melan-a cells with NADB caused a marked decrease in protein and mRNA levels of tyrosinase along with tyrosinase-related protein 1 and dopachrome tautomerase. To determine whether NADB reduces skin pigmentation, the dorsal skin of brown guinea pigs was shaved and irradiated with UV for 3 weeks using a solar simulator. Then NADB (2 or 1% in propylene glycol:ethanol:water = 5:3:2) was applied topically twice daily for 4 weeks. Visual inspection and Fontana-Masson staining both demonstrated that NADB resulted in lower skin pigmentation and total epidermal melanin in comparison to vehicle-treated areas. These findings suggest that NADB is useful in the treatment of hyperpigmentation.

Ion-trap tandem mass spectrometric analysis of squalene monohydroperoxide isomers in sunlight-exposed human skin

We previously discovered that squalene monohydroperoxide (SQ-OOH) was produced on human forehead skin and suggested that skin squalene (SQ) may be the principal target lipid for oxidative stress (e.g., sunlight exposure). Because of its six double bonds, SQ peroxidation can yield various positional hydroperoxide isomers. However, the structural characterization of skin SQ-OOH isomers has never been reported. Here, we prepared pure SQ-OOH isomers and developed an analytical method for SQ-OOH isomers using a quadrupole/linear ion-trap mass spectrometer (QTRAP) MS/MS system. Collision-induced dissociation produced specific fragment ions for each SQ-OOH isomer, which permitted discrimination between SQ-OOH isomers by multiple reaction monitoring (MRM). When lipid extract from human forehead skin was subjected to LC-MS/MS with MRM, individual SQ-OOH isomers could be separated and detected with a sensitivity of 0.05 ng/injection. The total concentration of SQ-OOH isomers in forehead skin was approximately 956 microg/g skin lipids, but it increased up to 2,760 microg/g skin lipids after 3 h of sunlight exposure. The LC-MS/MS method was useful for investigating the peroxidation mechanisms of SQ as well as SQ-OOH-mediated skin disorders.