C. Coiffard

Comparison of cytotoxicity of various surfactants tested on normal human fibroblast cultures using the neutral red test, MTT assay and LDH release.

We used the neutral red test, MTT assay and lactate dehydrogenase (LDH) release to compare the potential cytotoxicity of six surfactants belonging to different classes—three non‐ionic surfactants (Triton ×100, octylphenoxypolyethoxy alcohol, from Orion; Tween 60, polyoxyethylene (20) sorbitan monostearate, from ICI Speciality Chemicals; Tween 80, polyoxyethylene (20) sorbitan monolaurate, from Labosi), two anionic surfactants (Texapon K1298, sodium lauryl sulphate, from Henkel; Texapon N40, sodium laurylether sulphate, from Henkel) and one cationic surfactant (benzethonium chloride, from Siber Hegner)—on human fibroblast cultures. According to the LC50 (μg ml−1), the tested surfactants can be classified in the following order of increasing cytotoxicity: Tween 80 < Texapon N40 < Tween 60 < Texapon K1298 < Triton ×100 < benzethonium chloride. Copyright

High-performance liquid chromatographic method for the comparison of the photostability of five sunscreen agents

Sunscreen agents are commonly used in cosmetic products to filter out noxious radiation in sunlight. A convenient high-performance liquid chromatographic (HPLC) method for the quantification of five sunscreens after irradiation has been selected. We used this analytical method to compare the photostability of benzophenone-3, PEG-25 PABA, octyl dimethyl PABA, 4-methylbenzylidene camphor and butyl methoxydibenzoylmethane, at levels in the range of 25-60 microM. The assay was carried out, using a C8 column with a methanol--water mobile phase. The detector was set at a wavelength of 300 nm. The assay was linear with the following limits: 0.2 microgram ml-1 for benzophenone-3, 1 microgram ml-1 for PEG-25 PABA, 0.15 microgram ml-1 for octyl dimethyl PABA, 0.1 microgram ml-1 for methylbenzylidene camphor and 0.05 microgram ml-1 for butyl methoxydibenzoylmethane. The half-lives calculated indicate a very good photostability of the sunscreens studied and permit to classify amongst themselves.

In vitro correlation between two colorimetric assays and the pyruvic acid consumption by fibroblasts cultured to determine the sodium laurylsulfate cytotoxicity

The target of this research was to determine the cytotoxicity of sodium laurylsulfate on single-layer cultures of human fibroblasts, using two colorimetric methods (neutral red and MTT tests) and the evaluation of the pyruvic acid consumption by the cells. For the determination of the cytotoxicity by colorimetric tests, we have determined the absorbance at 540 nm using a spectrophotometer. Pyruvic acid, present in the culture medium, is the mitochondrias C3 energetic metabolite. So, a measure of the cells consumption of pyruvic acid was developed. The reaction is as follows: Pyruvic acid + NADH --> Lactic acid + NAD+ and the enzyme employed is the LDH (lactate dehydrogenase). This method can be used to measure cytotoxicity, proliferation, and the cells activation. The method is rapid, precise, and lacks any toxic byproduct. The absorbance was measured using a spectrophotometer at 340 nm. The consumption of pyruvic acid follows upon the fibroblasts growth. Sodium laurylsulfate cytotoxicity test after 24 h shows that the NR colorimetric test and the pyruvic acid consumption are correctly correlated (r = 0.91, alpha = 0.05). This dosage can be used to study the barrier properties of the corneocyte layer without destroying the artificial skin.

Free amino acid analysis of five microalgae

The HPLC separation of fluorescent o-phtaldialdehyde (OPA) derivatives has been applied to the assay of free amino acids from five microalgae commonly used in aquaculture: Tetraselmis suecica, Skeletonema costatum, Chaetoceros calcitrans, Thalassiosira sp. and Isochrysis galbana, as part an assessment of their potential use in cosmetic products. Thirteen free amino acids were analyzed using High Performance Liquid Chromatography. There were considerable differences between species. However, four amino acids were responsible for more than 60% total concentration in all species: ASP, GLU, ARG and TYR; the next most important (accounting for less than 30%) were: ALA, VAL, PHE and LYS.

Monoammonium glycyrrhizinate stability in aqueous buffer solutions

The objective of this research is to evaluate the thermal stability of monoammonium glycyrrhizinate. Thermodegradation of solutions of monoammonium glycyrrhizinate at various temperatures (50, 70 and 90 degrees C) was studied. This degradation appeared to follow first-order kinetics independently of temperature and was found to be pH dependent. The experiments revealed an activation energy (Ea) of about 33 kJ mol-1 and a t 90% of about 3 years at 20 degrees C in a pH range from 7 to 9. So it can be concluded that monoammonium glycyrrhizinate is stable in a pH range from 7 to 9. It can be interesting for use in oral care or in food industry.

Effect of pH on Sodium Usnate Thermostability in Dilute Aqueous Solutions

The objective of this study is the evaluation of sodium usnate thermostability. To this end, we used an isothermal method at four temperatures (40, 50, 60, and 70°C). The thermodegradation of dilute aqueous solutions of sodium usnate was studied at various pH values. This degradation appeared to follow first‐order kinetics. Under the best stability conditions (pH = 8), the experiments gave a t90% of 54.58 days, and a t90% of 359.07 days at 20°C.

Photodegradation study of sodium usnate solution: influence of pH.

Photodegradation of 2.6 x 10(-5) M aqueous solutions of sodium usnate at various pH was studied. Photodegradation appeared to follow first-order kinetics and was found to be pH dependent. The degradation rate constant was calculated to be 9.20 x 10(-4) min-1, 5.93 x 10(-4) min-1, 9.69 x 10(-4) min-1, and 9.88 x 10(-4) min-1 at pH 6, pH 7, pH 8, and pH 9, respectively.

Influence of temperature on the degradation of climbazol in aqueous diluted solutions

Abstract The objective of this research is to evaluate the stability of climbazol. Thermodegradation of solutions of climbazol at various temperatures (50, 70 and 90°C) was studied. This degradation appeared to follow first-order kinetics whatever the temperature. The experiments revealed an activation energy Ea of 5.4 kcal mol−1 and a time necessary to obtain a decrease of 10% of the initial concentration, t90%, of 81.9 days for climbazol in aqueous diluted solution at 20°C.