Alkyl Esters of L-Ascorbic Acid: From Synthesis to Applications

MARÍA LAURA FANANI; RAQUEL V. VICO; LUCIANO BENEDINI; EMMA PARSONS

Ascorbic Acid: Properties, Synthesis and Applications

Nova Science Publishers, Inc.

Lugar: Hauppauge, N.Y.; Año: 2016;

Antioxidants are important additives in food, cosmetics and pharmaceutics, and vitamin C being one of the best positioned for industrial applications. The usage of native L-ascorbic acid is limited to water containing media because its hydrophilic nature. To overcome this issue an extensive effort has been made to develop new amphiphilic derivatives capable to be applied in lipophilic environments. The alkyl derivatives obtained through esterification of the primary hydroxyl group of L-ascorbic acid with different reagents are the most widely studied compounds from the synthetic, physicochemical and pharmaceutical point of view as well as are those most used in commercial formulations. This book chapter offers a comprehensive revision of the bibliography regarding the main pathways to synthesize these alkyl derivatives, involving enzyme catalysis and esterification in acidic or alkaline media to obtain the alkanoyl-6-O-ascorbic acid esters (ASCn). This information is presented together with their stability properties. Besides its antioxidant properties, the ASCn family has been used in different pharmacological preparations per its amphiphilic nature. The presence of the acyl chain provides the capacity to self-organize into micelles and coagel when suspended in water. The knowledge of the phase behaviour of surfactants in aqueous media is relevant for the understanding of the properties of these systems and is vital for the numerous industrial applications. These, along with a revision of surface properties of the ASCn family are developed in this chapter. The ASCn amphiphiles, when self-organized at the air-water interface form Gibbs and Langmuir monolayers with a large variety of stability, phase states and surface textures depending on the length of the acyl chain moiety and ionization conditions. Furthermore, the different members of ASCn family have some differences in its effectiveness for determined pharmaceutical purposes. Then, the physicochemical properties of each member of this drug family may be determinant for their efficacy in those pharmaceutical processes, in particular those related to surface phenomena and interaction with biomembranes. Cell membranes are the first contact of lipophilic drugs with cells and often form a reservoir. Then, the drug/membrane interaction is a fundamental condition for its pharmacological function and a potential regulatory point. Here are revised some attempts made to experimentally explore the interaction and general physicochemical effect of the ASCn family members when they are incorporated into model lipid membranes under controlled conditions.Finally, some approaches in the use of ASCn in biomedicine were revised. Those attempts were based mainly on I) their antioxidant capability because the presence of ASCn derivatives in formulations could prevent degradation of drugs sensitive to light exposure, oxidizing or reactive oxygen compounds and/or II) the capacity of ASCn to form micelles, coagels and liquid crystals, which can modify some properties of the medium and act as drug delivery nanostructures. The new strategies in the use of ASCn comprise examples from liposome-based encapsulated nanoparticles to novel adjuvant activity of ASCn liquid crystals with high immunological efficiency.