Monolaurin

PHARMACOLOGICAL ACTIVITIES AND CLINICAL TRIALS Acquired immunodeficiency syndrome activity. Coconut oil and monolaurin —a coconut oil byproduct— were administered to 12 women and 3 men who were in the early stage of human immunodeficiency virus infection. Ten patients took different doses of monolaurin, and five patients took coconut oil. It was believed that the treatment would lead to higher CD4 counts and a lower viral load. The trial was abandoned because it received only lukewarm approval from the governmenC s ... 

Monolaurin Dried 1-Monomyristin Dried Anthranilic acid Fr o S Arachic acid Fr °°... 

The antifungal properties of fatty acids and several of their derivatives such as amides and methyl esters have been reviewed (113) as have their antimicrobial activities (114). Monolaurin (the ester of 1 auric acid and glycerol) is the most potent lipid derivative tested to date with regard to antibiotic activity. 

A similar effect was noted in separate investigations by another group [108], Oil-in-water HIPEs, where the oil phase contained aromatic or halogenated liquids, were difficult or impossible to form, with nonionic surfactants. This was postulated to be as a result of interactions between the polar ethylene oxide groups of the surfactant and the aromatic or halogenated solvents, which are more polar than hydrocarbons. Water-in-oil systems also displayed this tendency [21] however, w/o HIPEs with m-xylene as the oil phase [13] could be produced with monolaurin as nonionic emulsifier, due to stronger intermolecu-lar interactions at the interface. 

Index Entries Monolaurin immobilized lipase esterification experimental design solvent-free medium. 

The objective of the present work was to study the synthesis of monolaurin by direct lipase-catalyzed esterification between glycerol and lauric acid without any solvent or surfactant. The effects of lauric acid/ glycerol molar ratio, enzyme concentration, and temperature were studied using an experimental design. The reuse of the commercial immobilized lipase, to reduce the process cost, was also investigated. 

The effects of different variables on a process can be determined using experimental design methodology, which employs a reduced, but meaningful, number of experiments (10). The statistical analysis of monolaurin molar fraction (Ymon) was made by means of a two-level-three-factors central composite design with six star points and six central points. The experimental data were analyzed using STATISTICA for Windows, release 5.5, produced by StatSoft. 

An experimental design technique was used to identify the best conditions to produce monolaurin. The basic idea was to devise a small set of... 

A central composite design for three factors was used to generate 20 combinations. The effects of independent variables—acid/glycerol molar ratio (R), temperature (T), and enzyme concentration (E)—on the response (i.e., the monolaurin molar fraction at 4 h) were investigated. The upper and lower limits of each variable were chosen based on published data and preliminary studies (12,13). Actual independent variables or factors and their corresponding coded levels are presented in Table 1. 

The enzymatic synthesis of monolaurin was quantified in terms of molar fraction of each component in the nonpolar phase (lauric acid, mono-, di-, and trilaurin), and monolaurin molar fraction was chosen to define the best reaction conditions. The selectivity parameter, defined as the ratio between concentrations of monolaurin and total concentration of reaction products (mono-, di-, and trilaurin), was also evaluated. 

Table 2 presents the analysis of the main effects and interactions of the factors (linear and quadratic) for the chosen response and their statistical significance (p value). It can be observed that the main factor E (linear and quadratic) and two main factors (R and T quadratic) are the important ones with a statistically significant effect on the response of monolaurin molar fraction (p < 0.05). 

A useful plot for identifying factors that are important is a Pareto chart. The graph in Fig. 1 shows the t-test values in the horizontal axis and also includes a vertical line to indicate the p value (an effect that exceeds the vertical line maybe considered significant). As observed in the Pareto chart, enzyme concentration is the most significant variable influencing monolaurin molar fraction. 

Figure 2 shows the three-dimensional plot for the response of monolaurin molar fraction vs temperature ratio and enzyme concentration at a molar ratio of 1.0 and reaction time of 4 h. The highest Ymm values were reached at temperatures between 54 and 56°C and an enzyme concentra-... 

Data analysis led to the optimal conditions 55.5°C, molar ratio of 1.0, and enzyme concentration of 4.3% (w/w) corresponding to monolaurin molar fraction (43.3%). The best measured values are closer than those obtained from the statistical analysis. ANOVA demonstrated that modeling was successful with a coefficient of determination (R2) of 0.964. The plot... 

Fig. 3. Influence of variables (R, T, and E) on monolaurin molar fraction and monolaurin selectivity after 4-h reaction.

According to Fig. 1, the enzyme concentration is the variable presenting higher statistical importance on monolaurin synthesis. Therefore,... 

Fig. 4. Comparison of experimental and calculated values of monolaurin molar fraction.

The effect of temperature on monolaurin synthesis was also statistically significant. The best temperature tested was 55°C. Figure 6 shows the effect of temperature on monolaurin molar fraction during 6 h of reaction using a concentration of enzyme preparation of 3.0% (w/w) and substrate molar ratio of 1.0. An increase in temperature (above 55°C) did not favor... 

Fig. 5. Effect of Lipozyme IM-20 concentration on molar fraction in monolaurin for synthesis performed at 55°C using R = 1.0.

Fig. 6. Effect of temperature on monolaurin synthesis (molar fraction) carried out for 6 h with lauric acid /glycerol molar ratio of 1 and 3.0% (w/w) Lipozyme IM-20.

Considering the results presented, the best experimental conditions used for monolaurin synthesis were 55°C, an enzyme concentration of 3% (w/w), and use of the stoichiometric molar ratio of reagents. Figure 7 shows the nonpolar phase for monolaurin synthesis under these conditions. The final product, obtained after 6 h of reaction, was 45.5% monolaurin, 26.8% dilaurin, 3.1% trilaurin, and 24.6% lauric acid. 

Machado et al. (1) studied the synthesis of monolaurin from lauric acid and glycerol employing commercial Beta, Y, and Mordenite zeolites as catalysts. The optimized conditions for the monolaurin synthesis... 

A fully central comp osite design was applied to optimize monolaurin synthesis. A three factorial design was proven effective to establish the influence of the variables on the monolaurin synthesis. The central composite design procedure was adopted to optimize variables affecting the monolaurin molar fraction. 

Statistical analysis showed that within the experimental range considered, the most important factor was enzyme concentration. The temperature also affected the monolaurin molar fraction. This factor had a negative influence. According to these results, the maximum monolaurin molar fraction (43.3%) was achieved at 55°C, a molar ratio of 1.0, and an enzyme concentration of 4.3% (w/w) within the range studied. 

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