Vitamin C is a natural anti-aging and whitening bioactive ingredient that has been widely used in cosmetic and dermatological products thanks to its favorable effects on the skin [1
], which include radicals scavenging, collagen biosynthesis, and the suppression melanin formation [2
]. The strong antioxidant properties and the ability to prevent skin aging make ascorbic acid, also known as vitamin C, one of the most interesting active ingredients for the cosmetic industry. However, its employment in products for topical use (skin care, deodorants, hair dyes, etc.) is severely limited because of its instability. In fact, ascorbic acid tends to rapidly degrade due to an oxidation process, causing a consequent decline in the title and then the loss of activity [6
]. Various strategies have been pursued in order to avoid this problem, for instance the exclusion of oxygen or the use of air impermeable packaging, and the use of carrier and release systems [7
] that protect the vitamin C from oxygen, water, and other components that may be included in the cosmetic formulation. A very stable form of ascorbic acid is vitamin C ascorbyl tetraisopalmitate (VC-IP). VC-IP (Figure 1
) is stable at high temperatures and has good solubility in oils. It exhibits excellent percutaneous absorption and effectively converts into free vitamin C in the skin to perform various physiological functions [8
]. VC-IP is approved as a quasi-drug active in Japan (at 3 wt %). It is also registered in Korea as a functional ingredient for skin lightening at 2 wt % concentration.
VC-IP is an oil-soluble raw material in the form of a colorless to pale yellow liquid, and for this reason some cosmetic applications are precluded. In fact, it is difficult to dissolve VC-IP in water or use it in compact formulations for make-up and color cosmetics. Therefore, it could be very interesting and strategic to find a formulation of VC-IP in powder form in order to expand the field of application of this raw material. The idea of this study is to include VC-IP in a solid matrix in order to develop a new cosmetic raw material in micro-powder form. This strategy could allow the easy dispersion of the active ingredient both in water and oil phases of semisolid formulations, as well as allow its direct use in compacts and other solid formulations for color cosmetic applications. The confinement of the active ingredient further decreases the oxidative degradation of VC-IP, because even in case of formation of by-product radicals, it is likely that the radicals recombine, bringing the molecule to the initial state. Thus, this strategy can greatly improve the stability of VC-IP. Moreover, the use of a carrier to vehiculate VC-IP can successfully improve the release of the active ingredient, producing a formulation with modified and prolonged delivery. Taking into account that VC-IP is a neutral molecule among the different types of solid drug carriers [10
], Cyclodextrin and mesoporous SBA-15 have been chosen as the best candidates for the purpose of this work. Cyclodextrin are cyclic (α-1,4)-linkedoligosaccharides of α-d
-glucopyranose, containing a relatively hydrophobic central cavity and hydrophilic outer surface. During the past two decades, cyclodextrin and their derivatives have attracted considerable interest in the pharmaceutical field because of their potential ability to form complexes with a variety of drug molecules. Cyclodextrin are used to increase the solubility of water-insoluble drugs through the formation of inclusion complexes. The hydrophobic cavity of cyclodextrin is capable of trapping a variety of molecules to produce inclusion complexes [13
]. Three types of cyclodextrin that are most known and widely used and are α, β, and Υ. The difference between them is the dimension of the cavity [13
]. Υ-cyclodextrin was chosen because it offers the biggest cavity, which was considered adept to host the active ingredient of VC-IP, which is an ester in which ascorbic acid is covalent linked to four palmitates, (C 16), with a big steric hindrance.
SBA-15 (Santa Barbara Amorphous type material) is an ordered mesoporous silicate. Due to its unique properties, it appears to be an ideal solution for the encapsulation of pharmaceutical drugs, proteins, and other biogenic molecules. In addition, it is very effective in terms of the enhancement of active dissolution [14