摘要:

SynopsisThis paper assesses the suitability of UVB induced skin erythema measured by reflectance spectrophotometry in humans as a model for differentiating topical efficacy of free radical scavengers. Two different formulations (aqueous gels and O/W emulsions) of each active compound (tocopherol, tocopherol acetate, superoxide dismutase (SOD), glutathione, ascorbyl palmitate) were tested on healthy human volunteers before and after skin exposure to UVB radiation. Skin erythema was monitored by calculating erythema index values from the skin spectral data obtained using a reflectance spectrophotometer. The free radical scavengers tested were not able to inhibit UVB induced skin erythema from both formulations when they were topically applied before UVB irradiation. Applying the free radical scavenger formulations after skin exposure to UVB radiation, glutathione and SOD showed the best ability in inhibiting the induced erythema (percentage inhibition 53.3 and 41.6%, respectively from gels). Tocopherol and tocopherol acetate inhibited UVB skin erythema by 27% while ascorbyl palmitate showed a poor efficacy. For all the active compounds tested, no significant difference was observed comparing the results obtained from gels to those from emulsions. Liposomal gel formulations containing the free radical scavengers which showed the best activity (SOD and glutathione) were prepared and topically applied after skin exposure to UVB radiation. SOD and glutathione liposomal formulations were more effective than the corresponding conventional gels. The proposed model, if validated by further studies, could be useful for differentiating the effectiveness of free radical scavengers in inhibiting photoaging due to long‐term sunlight skin exposur

ISSN:0142-5463    

DOI:10.1111/j.1467-2494.1995.tb00113.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryOpto‐thermal transient radiometry (OTTER) is a non‐invasive measurement technique, well suited forin vivoskin research. Its excitation and detection wavelengths can be selected to give a high sensitivity to stratum corneum hydration. This is demonstrated with measurements of hydration changes resulting from occlusion with a neoprene cover and with a topical application of an occlusive preparation. In the former case, the hydration was found to recover to normal levels upon exposure to atmospheric conditions in a characteristic time of 15 min. In the latter case, a topical application of petroleum jelly was found to lead to a doubling of stratum corneum hydration over 2h. This ability to measure hydration changes in the presence of topical hydrating agents is thought to be a particularly valuable property of the OTTER technique. With a different choice of excitation and detection wavelengths, OTTER can be used to measure skin thickness, from the surface down to the vascular bed. This technique was used to measure a skin thickness map of the ventral surface of the forearm of a volunteer, showing distinct thickening near the wrist and ulna. Another use of this technique is the study of changes in subcutaneous blood distribution associated with erythema. As a demonstration of this, blood distribution changes brought about by the topical application of a salicylate/nicotinate preparation were studied. The main finding is that the subcutaneous blood spreads towards the surface, with the mean depth decreasing from 63 μm to

ISSN:0142-5463    

DOI:10.1111/j.1467-2494.1995.tb00114.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

SummaryFrom initial rate studies of morpholine nitrosation in aqueous media by nitrite ion in the presence of formaldehyde at pH 5–7 and 25°C, four potential pathways are revealed for the concurrent formation of nitrosamine contaminants in cosmetic and toiletry products. Three of the pathways involve conventional electrophilic nitrosation by XNO reagents of both neutral amine andN‐hydroxymethylamine compounds obtained by prior reaction with formaldehyde. The fourth pathway involves a nucleophilic reaction by nitrite ion with the iminium ion derived fromN‐hydroxymethylamine. For morpholine, reactionviaXNO reagents is substantial at pH 5 only, whereas the iminium ion pathway is pre‐eminent at pH 7. The concurrent formation of nitrosamines by mechanistically different pathways implies that combinations of nitrosation inhibitors are necessary to minimize contamination of cosmetic and toiletry products. For these different pathways, novel inhibitory compounds are described which fulfil the usual acceptance criteria for cosmetic and toiletry materials. The efficacy of these compounds is assessed againstN‐nitrosomorpholine formation in the presence of formaldehyde. These include erythorbate, ascorbate, pentanedione and pyranone compounds for the XNO pathways (pH 6) and neutral organic and inorganic salts for the iminium ion pathways (pH 7). Preliminary results for both a bath gel and a cream‐base formulation deliberately adulterated with morpholine, diethanolamine, nitrite and a preservative which releases low levels of formaldehyde on decomposition show better than 90% inhibition of nitrosamines by selected pairs of inhibitor compounds on storage at 40°C over several months. This novel technology is the subject of a worldwide paten

ISSN:0142-5463    

DOI:10.1111/j.1467-2494.1995.tb00115.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY