Synthesis of Eugenol Esters by Lipase-Catalyzed Reaction in Solvent-Free System

Abstract

Enzymatic esterification of eugenol is a matter of great scientific and technological interest due to the well-known drawbacks of the chemical-catalyzed route as well as the potential use of produced compounds as natural antimicrobials. This work reports the maximization of eugenil acetate production by esterification of eugenol and acetic anhydride in a solvent-free system using Novozym 435 as catalyst. The antimicrobial activity of eugenol and eugenil acetate was also determined. The operating conditions that maximized eugenil acetate production were 50 °C, eugenol to acetic anhydride of 1:3, 150 rpm, and 5.5 wt% of enzyme, with a conversion of 99 %. A kinetic study was performed to assess the influence of substrates molar ratio, enzyme concentration, and temperature on eugenil acetate yield. Results show that an excess of anhydride, low enzyme concentration (1 wt%), and 60 °C afforded nearly complete conversion after 6 h of reaction. The highest antimicrobial activity of eugenil acetate was observed against Acinetobacter sp. (48.66 mm) at concentration of 20 μL. Results indicate that the esterification of eugenol improved its antimicrobial properties. New experimental data on enzymatic esterification of eugenol and acetic anhydride are reported in this work, showing a promising perspective to overcome the inconvenient of the chemical-catalyzed route for obtaining antimicrobial natural compounds.

Antimicrobial and Antioxidant Activities of Clove Essential Oil and Eugenyl Acetate Produced by Enzymatic Esterification

“…Similar results were obtained by Chiaradia et al [6]. The authors demonstrated that after the first 30 min of reaction, the highest conversions were obtained for the enzyme concentrations of 1, 5.5, and 10 %, respectively, and 20, 46, and 51 %.…”

“…Although a number of works were presented in the literature about the biological properties of clove oil and eugenol [6][7][8], a lack was found related to the evaluation of the antimicrobial and antioxidant potential of eugenol esters obtained by enzymatic catalysis for further application in food and cosmetic industries. Several works relate the synthesis of esters from acids and anhydrides by enzymatic catalysis in organic and solvent-free systems; however, just a few use eugenol as substrates [9][10][11][12][13].…”

Antimicrobial Activity and Chemical Composition of Two Essential Oils and Eugenol from Flower Buds of

“…Taking into consideration that in our study the only major difference between the two EOs (freshly prepared and commercial) is the presence of eugenyl acetate, one is tempted to attribute the higher overall antimicrobial activity of the freshly hydrodistilled/dried EO to its presence. This assumption finds support in recent study by Chiaradia and co-workers [56] who synthesized pure eugenyl acetate by lipase-catalyzed reaction in solvent-free system and tested its antimicrobial activity in parallel with eugenol employing diffusion disk technique. The eugenyl acetate led to an increase in the antimicrobial activity (16 bacteria tested) when compared to pure eugenol (i.e the acetylation of eugenol improved its antimicrobial properties).…”

Toxicity of clove essential oil and its ester eugenyl acetate against Artemia salina

“…These results are similar to other studies from the literature. Chiaradia et al (2012) achieved a conversion of about 99% in the esterification of eugenol and acetic anhydride using a commercial immobilized lipase from Candida antarctica as catalyst, at acetic anhydride to eugenol molar ratio of 3:1, enzyme concentration of 5.5 wt% (based on the total mass of substrates), 50 °C in 6 hours of reaction. Chaibakhsh et al (2012) synthesized eugenyl caprylate using Lipozyme TL IM as catalyst in solvent-free system, and obtained a maximum reaction yield of 72.2% at 65 °C, 250 rpm, 100 mg of enzyme, caprylic acid do eugenol molar ratio of 1:2 after 4.5 hours of reaction.…”

“…The oil also presents other components of terpenes source as β-cariofilen, α-humulen and eugenyl acetate (Chaieb et al, 2007;Dzamic et al, 2009). Eugenol has different biological properties confirmed: bactericide (Moon et al, 2011), antifungal (Rana et al, 2011), larvicidal (Pandey et al, 2013), antioxidant (Chiaradia et al, 2012;Vanin et al, 2014), anti-inflammatory (Daniel et al, 2009), among others.…”