*2.5.2. Mechanism of action*

In particular, enzymes appear to be very effective for the synthesis of molecules involving the grafting of a lipophilic moiety or a hydrophilic one. This review will be described and discussed in some of the recent works in the field of enzyme-assisted acylation of fatty acids with phenolic compounds in order to modify the hydrophilic/lipophilic properties of the initial molecules to obtain new products with multifunctional properties combining, for example, antimicrobial, antioxidant and emulsifying properties. The enzymatic synthesis of phenolic lipids has been reported previously in Refs. [10, 45, 47–49]. A lot of enzymes can be used in the synthesis of PL and selectivity is the most important characteristics of enzymes used in phenolic lipid synthesis. Lipase is the most enzymes used in this type of process because of high selectivity, lower overall reaction time and fewer side reactions when compared with chemical methods [50]. An example of a synthesis reaction catalyzed by the lipase is shown in **Figure 4**. This overwhelming interest is based largely on consumers' desire to maintain overall well-being with minimal effort and an industries' ability to respond to this need. Furthermore, with the consumption of manufactured foods continually on the rise, there is a distinct advantage to providing more healthful choices for consumers. The concept of a natural phenolic lipid composed of a longchain aliphatic and phenolic moiety readily fits this mold, particularly since the inclusion of unsaturated lipids into these compounds could result in additional nutritional benefits. Lipases

96 Phenolic Compounds - Natural Sources, Importance and Applications

constitute the most important group of biocatalysts for biotechnological applications.

Lipase enzymes are defined as glycerol ester hydrolyses that can hydrolyze tri-, di-, and monoacylglycerols [52, 53]. Lipases are soluble in water as a result of their protein nature, but it could act on lipids, which are water insoluble, at the interface between oil and water [53, 54] and catalyze esterification and transesterification in addition to the hydrolytic activity on TAG [55–57]. Lipases are originated from a wide variety of sources including animals, plants and microorganisms. Animal lipases include pregastric esterase, pancreatic lipase, and lingual lipases [53]. Plants such as wheat germ and castor beans also contain lipases [58, 59]. Finally, microbial sources including yeast (*Candida* and *Geotrichum*), molds (*Rhizopus*, *Aspergillus*), and bacteria (*Bacillus*, *Pseudomonas*) [60]. Lipases are widely used because of their ready availability, low cost of production, utility in food, biotechnology, and pharmacology [61]. Novel biotechnological applications have been successfully established using lipases for the synthesis phenolic lipids, the production of pharmaceuticals, agrochemicals, and flavor compounds [52, 62, 63]. Moreover, the use of lipases in the food industry is increasing due to

**Figure 4.** Enzymatic synthesis reaction capsiates (fatty vanillyl alcohol acid ester) catalyzed by lipase Novozym 435® [51].

the need for the production of esters, biodegradable polyesters, and specific FAs [64].

**2.5. Lipases**

*2.5.1. Definition, sources, and applications*

Lipase-catalyzed reactions have been gained a lot of interest over the last years; the major reason for this is that lipase can promote either ester formation or ester hydrolysis. Moreover, lipase can control the acylation and deacylation to produce specific fatty acids and triacylglycerols (i.e., phenolic lipids). Lipase-catalyzed reactions can be classified into three groups which are hydrolysis, esterification, and transesterification [65].
