Asiatic acid, madecassic acid, and asiaticoside, terpenoids with an ursane skeleton, were tested separately and in combination on skin human fibroblast collagen I synthesis in vitro. In the absence of ascorbic acid, the mixture as well as each individual component stimulated collagen I synthesis to a similar extent. In the presence of ascorbic acid, the level of collagen I secretion was higher for each individual component and for the mixture. A comparison of asiaticoside and asiatic acid shows that the sugar moiety of the molecule does not seem to be necessary for this biological activity.

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The internal stratum corneum lipid composition was investigated in relation to depth in vivo in healthy human volunteers by extraction following one, three or five strippings. Automated multiple development high-performance thin-layer chromatography (AMD-HPTLC) and gas chromatography (GC) followed by normalized principal component analysis showed a decrease in the amount of lipids extracted after one, three and five strippings. Between levels 0, 1, 3 and 5 the stratum corneum lipid composition showed an increase in phospholipids and cholesterol-3-sulphate at level 3, a decrease in ceramide, cholesterol and free fatty acids after level 1, and a slight decrease in sterol esters at level 3. Lipids extracted after three strippings displayed a characteristic composition with an increase in the proportion of phospholipids and cholesterol-3-sulphate. Free fatty acid analysis in relation to depth revealed a decrease in the amounts of C14:0, C16:0, C16:1, C18:0 and C18:1 between levels 1 and 5 and an increase in the C24:0. A decrease in the unsaturated/saturated chain ratio with depth was also observed, reflecting a greater decrease in unsaturated than saturated free fatty acids. A decrease in the ratios of free fatty acids to cholesterol and free fatty acids to ceramides after three and five strippings, respectively, and previously reported results, confirm the importance of this level of stratum corneum lipids in skin barrier properties.

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