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Aquaporins: Stimulation by Vitamins, Steroids and Sugar Alcohols
By: Bud Brewster, C&T magazine
Posted: October 30, 2008, from the November 2008 issue of Cosmetics & Toiletries.
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A 2006 LVMH patent9 disclosed that by selecting particularly polar solvent media for the plant Ajuga turkestanica it is possible to obtain ecdysteroids and other active ingredients whose associations make it possible to improve the differentiation of keratinocytes, which in turn makes it possible to improve the hydration of the skin and obtain a particularly effective antiaging activity. Furthermore, the inventors observed that the extracts and the associations of these ingredients are particularly effective in regulating the water fluxes in the epidermis, an activity that the inventors relate to the activity of the extracts in the regulation and/or functionality of AQP3, thereby affording a better hydration of the basal layers of the epidermis. Examples of formulations containing ecdysteroids were previously reported.10
A sugar alcohol—also known as a polyol—is a hydrogenated form of carbohydrate whose carbonyl group (aldehyde or ketone, reducing sugar) has been reduced to a primary or secondary hydroxyl group. Sugar alcohols are commonly used for replacing sucrose in foodstuffs. Examples of sugar alcohols include glycerol, also known as glycerin, as well as glycol, xylitol, sorbitol and others. It has been known since 1994 that AQP3 is an aquaglyceroporin, meaning that it is permeable to both water and glycerin. Curiously, Japanese researchers recently identified a regulator factor for the transcription of AQP3, whose expression is repressed by insulin.11
A recent Beiersdorf patent12 discloses cosmetic and dermatological preparations comprising aquaporin stimulators, especially glyceryl glycosides, and the use thereof for improving moisturization of the skin. A glycoside is any of a group of sugar derivatives, widely distributed in plants, that upon hydrolysis yields a sugar and one or more other substances. Many plants store important chemicals in the form of inactive glycosides; when these chemicals are needed, the glycosides are brought in contact with water and an enzyme, and the sugar part is broken off, making the chemical available for use. In a glyceryl glycoside, the sugar part is bound to glycerol by a condensation reaction.
“The particular glyceryl glycoside preferred by Beiersdorf is glyceryl glucoside, a term used in the specific case of glucose bound to glycerin,” said Cathrin Scherner, PhD, senior research scientist, Active Ingredient Profiles at Beiersdorf Research Center, in Hamburg, Germany.
“Glucose is linked to glycerin by a glycosidic bond of the amoneric oxygen. These kinds of monosaccharides are characterized by their hydrophilicity,” Scherner told C&T magazine. “Glyceryl glycosides have been widely known for many years. In particular, extremophile plants and different cyanobacteria produce glyceryl glycosides for osmotic adjustment in order to be able to survive in extremely dry or salty environmental conditions.” Structures of two glyceryl glucosides are shown in Figure 1. Some organisms produce the 1-O-isomer; others produce the 2-O-isomer.