Abstract
In this research, eugenyl acetate, a compound with flavoring, antioxidant, and antimicrobial properties, was obtained from essential oil of clove (Syzygium aromaticum) via liquid lipase-mediated acetylation. Clove essential oil was extracted by drag water vapor from dry flower buds and its physic-chemical characteristics were analyzed. For the enzymatic synthesis, an extensive evaluation of reaction parameters was accomplished through employment of distinct reaction temperatures, acetic anhydride to eugenol molar ratios, enzyme loads, and three different lipases (a lyophilized enzyme produced by solid-state fermentation of sunflower seed with Penicillium sumatrense microorganism and other two commercial lipases - Lipozyme TL 100L and CALB L). The product eugenyl acetate was confirmed by 1H-NMR, 13C-NMR Distortionless Enhancement by Polarization Transfer (DEPT 135), and Heteronuclear Multiple Bond Correlation (HMBC). Through optimized conditions (55 °C, acetic anhydride to eugenol molar ratio of 1:1, 10 wt% of Lipozyme TL 100L), 91.80% of conversion after 2 h was achieved to the eugenyl acetate production. With the results obtained, it was possible to conclude that the use of lipases in liquid formulation is a promising alternative for the synthesis of essential esters largely applied on food, cosmetic, and pharmaceutical industries.
Highlights
Esters with low molecular weight represent an important chemical class of compounds derived from short-chain acids such as acetates, propionates and butyrates [1, 2]
An extensive evaluation of reaction parameters was accomplished through employment of distinct reaction temperatures, acetic anhydride to eugenol molar ratios, enzyme loads and three different lipases
With lipase loads inferior than 7 wt%, even using a high eugenol to acetic anhydride molar ratio, it was not possible to obtain satisfactory conversions, corroborating the hypothesis presented previously in the Pareto Diagram (Figure 1) that this variable is not significant for the eugenyl acetate (EA) conversion. Such finding allowed us to deduce that a minimum eugenol to acetic anhydride molar ratio of 1: 1 is the ideal to be used in the process
Summary
Esters with low molecular weight represent an important chemical class of compounds derived from short-chain acids such as acetates, propionates and butyrates [1, 2]. Such importance is due to the fact of numerous characteristics that allow its application in a wide area of industrial sectors that include food, pharmaceutical, energy, among others [3]. Eugenyl acetate (4-allyl2-methoxifenol acetate) is a phenylpropanoid with pale yellow aspect belonging to class of compounds named vanilloids [4] It is derivate from eugenol (2-allyl-4-methoxyphenol), which can be obtained by extraction from essential oil of clove (Syzygium aromaticum) [5]. Eugenol is the major component of the essential oil of clove with composition that range between 76 and 95 wt% [6,7,8]
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