Biocatalytic synthesis of ascorbyl esters and their biotechnological applications

Abstract

Ascorbyl fatty acid esters act both as antioxidants and surfactants. These esters are obtained by acylation of vitamin C using different acyl donors in presence of chemical catalysts or lipases. Lipases have been used for this reaction as they show high regioselectivity and can be used under mild reaction conditions. Insolubility of hydrophilic ascorbic acid in non-polar solvents is the major obstacle during ascorbic acid esters synthesis. Different strategies have been invoked to address this problem viz. use of polar organic solvents, ionic liquids, and solid-phase condensation. Furthermore, to improve the yield of ascorbyl fatty acid esters, reactions were performed by (1) controlling water content in the reaction medium, (2) using vacuum to remove formed volatile side product, and (3) employing activated acyl donors (methyl, ethyl or vinyl esters of fatty acids). This mini-review offers a brief overview on lipase-catalyzed syntheses of vitamin C esters and their biotechnological applications. Also, wherever possible, technical viability, scope, and limitations of different methods are discussed.

Lipase-Catalyzed Synthesis of Ascorbyl Oleate in Acetone: Optimization of Reaction Conditions and Lipase Reusability

“…Injection volume of reaction mixture, fifteen times diluted, was 10 μL. Methanol/H 3 PO 4 , 100/0.1 v/v , was used as eluent with a flow rate of 1 mL min 1 . Product was detected by UV detector at 235 nm.…”

“…At present, synthetic antioxidants such as BHT butylated hidroxytoluene and BHA butylated hidroxyanisole are being used to prevent oxidation of lipids in these products, but their application is questionable because of their potential toxicity 1 . Natural antioxidants which could be used as adequate substitute for this purpose are fatty acid esters of vitamin C, since they are lipophilic in distinction to vitamin C , their free radical scavenging capacity is high, their usage does not pass on any additional odor, flavor, and color to the product, and their degradation forms are not toxic unlike synthetic antioxidants 1 3 .…”

Enzymatic lipophilization of vitamin C with linoleic acid: Determination of antioxidant and diffusion properties of L-ascorbyl linoleate

“…Products with high lipid content are susceptible to deterioration caused by oxidation of unsaturated fatty acids which they contain. To alter polarity of L-ascorbic acid and improve its stability while saving its beneficial properties, variety of L-ascorbyl fatty acid esters were so far synthesized via esterification and transesterification using sulfuric acid (Cousins et al, 1977;Nickels and Hackenberger, 1986) or lipases as catalysts (Karmee, 2009;Stojanović et al, 2013a). At this moment, L-ascorbyl palmitate and stearate are being commercially produced in chemically catalyzed processes.…”

“…According to literature data, the most efficient biocatalyst of the process is lipase isoenzyme B from Candida antarctica (Karmee, 2009;Stojanović et al, 2013a). Liquid enzyme preparations are not adequate for application, due to negative influence of water present in reaction medium on equilibrium position.…”

“…Liquid enzyme preparations are not adequate for application, due to negative influence of water present in reaction medium on equilibrium position. Immobilized enzymes are almost exclusively applied since they could be easily separated from reaction mixture and reused in repetitive reaction cycles leading to decrease of process costs and increase of commercial competitiveness (Karmee, 2009 However, just like the other PUFAs, it is prone to autooxidation, which could be prevented by transforming it into ascorbyl ester (Adamczak and Bornscheuer, 2009). Its ascorbyl ester is valuable substance for food, cosmetic, and pharmaceutical industry owing to its nutritional, antioxidant, bleaching, skin conditioning, and skin protecting function (Ando et al, 1992;Song et al 2004).…”