Ionic Liquid‐Assisted Solubilization for Improved Enzymatic Esterification of Phenolic Acids

Abstract

Lipophilic derivatives of phenolic acids could greatly extend their applications in the lipophilic bioenvironment and food processing, therefore, developing an efficient lipophilization reaction system constitutes an interesting topic of biocatalysis. Low solubility of phenolic acids in most enzyme-benign solvents represents the main reason for the inefficiency of enzymatic production of lipophilic phenolic derivatives. This work reports a novel approach to improve Candida antartica lipase B (Novozym 435) catalyzed lipophilization of phenolic acids by means of ionic liquids (IL), trioctylmethylammonium trifluoroacetate (tOMA.TFA) assisted solubilization of the substrate. In this approach, the IL plays two major roles, namely, to dissolve phenolic acids at high concentration so as to create a homogeneous system with another substrate-1-octanol, and to be benign to the enzyme to keep the biocatalyst active; which is proved itself to be a correct strategy as improved conversion and volumetric productivity are obtained. The results showed that dosage of IL (denoted as the volume ratio of 1-octanol/tOMA.TFA), concentration of dihydrocaffeic acid (DHCA) and temperature are the key parameters governing the reaction efficiency. A maximum conversion of DHCA was achieved at the ratio of 1-octanol/tOMA.TFA 12:1 (v/v) (1-octanol/ DHCA, 38:1 (mol/mol)). A temperature of 70°C was correct to obtain optimal conversion of DHCA. Even though the conversion of DHCA was higher at lower concentrations of DHCA, the overall volumetric productivity (reaction rate) was much higher when a high concentration of DHCA (1.6 M) was applied, due to IL-assisted solubilization of DHCA. Remarkable enhancement of the conversions of ferulic and caffeic acids were achieved, when the same reaction approach (tOMA.TFA assisted solubilization) was applied to these two phenolic acids, indicating the general applicability of this novel approach.

Synthesis of novel octyl sinapate to enhance antioxidant capacity of rapeseed–linseed oil mixture

“…In addition, the antioxidant effect of CA, DHCA and FA esters in fish oil enriched mayonnaise and milk emulsions was estimated . Also an increase in the AC of alkyl phenolates with increasing alkyl chain length up to octyl phenolates was observed in previous reports . However, further alkyl chain elongation caused a decrease in AC of the phenolipids obtained.…”

“…In recent years, various esters of PAs were synthesised using a different type of esterification, in which the lipophilicity was essentially improved by an introduction of an additional alkyl side chain. Several PAs [CA, dihydrocaffeic (DHCA), cinnamic acid (CinA) FA, SA, CoumA] were extensively chemically and/or enzymatically modified by the grafting of various alcohols (methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, decanol, tetradecanol, dodecanol, hexadecanol, octadecanol, eicosanol) to obtain the lipophilised phenolics . Some reports demonstrated a novel approach to improve enzymatic synthesis of lipophilic cinnamic derivatives (1‐octyl dihydrocaffeate, 1‐pentyl, 1‐hexyl and 1‐heptyl ferulates) by using ionic liquid assisted solubilisation or reactor system, respectively .…”

“…Several PAs [CA, dihydrocaffeic (DHCA), cinnamic acid (CinA) FA, SA, CoumA] were extensively chemically and/or enzymatically modified by the grafting of various alcohols (methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, decanol, tetradecanol, dodecanol, hexadecanol, octadecanol, eicosanol) to obtain the lipophilised phenolics . Some reports demonstrated a novel approach to improve enzymatic synthesis of lipophilic cinnamic derivatives (1‐octyl dihydrocaffeate, 1‐pentyl, 1‐hexyl and 1‐heptyl ferulates) by using ionic liquid assisted solubilisation or reactor system, respectively . Additionally, response surface methodology was applied to optimise the conditions (temperature, time, enzyme‐to‐substrate ratio, alcohol‐to‐phenolic acid ratio) of enzymatic lipophilisation of CA, DHCA and FA using ethanol, butanol, hexanol, octanol, decanol and dodecanol in order to the optimal conversion .…”

One-pot esterification and amidation of phenolic acids

“…[5][6][7][8][9] The esterification and amidation of phenolic acids are practical techniques to improve their solubility and emulsification properties as well as enhance their antioxidant and antidiabetic activities. [10][11][12][13][14][15][16] The amidation of selected hydroxycinnamic acids and hydroxybenzoic acids improved their antioxidant activities. 14 The serine esters of phenolic acids exhibited superior antioxidative activity in heterogeneous systems.…”

Functional Ionic Liquids Catalyzed the Esterification of Ricinoleic Acid with Methanol to Prepare Biodiesel: Optimization by Response Surface Methodology

“…Ionic liquids (IL), as novel environmental friendly catalysts, due to non-volatile, thermal stability, and easy separation, have been used as green solvents and catalysts in many reactions [15,[20][21][22][23][24][25]. In this work, IL were used as catalysts and RA was used as acyl donor for biodiesel preparation.…”