Serum biochemical profile, enzymatic activity and lipid peroxidation in organs of laying hens fed diets containing cashew nut shell liquid
In addition, animals subjected to stress due to environmental temperature have a higher concentration of malondialdehyde (MDA) in plasma and tissues due to the production of free radicals (Klasing, 1998) and reactive substances to oxygen, presenting correlation with the loss of steroidogenic functions, resulting in a decrease in laying egg production.
Accordingly, supplementation of vitamins and antioxidant additives can be an important way to mitigate the adverse effects of heat stress in birds (Naziroglu et al., 2000; Hashizawa et al., 2013). In this regard, among other additives, organic acids with antioxidant activity in vitro have been evaluated in the feeding of laying hens.
The cashew nut shell liquid (CNSL) is a viscous, oily, caustic, dark‐brown substance that can be extracted from the cashew nut (Chaves et al., 2010), in which it accounts for 25% of the total weight. According to Trevisan et al. (2006), CNSL is one of the sources richest in isoprenoid phenolic lipids such as anacardic acid (derived from salicylic acid), cardols and methyl‐cardols (derived from resorcinol), and cardanols (a monophenol).
A variety of biological properties, including antioxidant and antibiotic activities (Andrade et al., 2011; López et al., 2012), have been reported for CNSL compounds. Morais et al. (2010) observed that anacardic acid has a gastro‐protective effect associated with the antioxidant mechanisms. Toyomizu et al. (2000) found that anacardic acid shows antioxidant activity in the prevention of oxidative damages in the mitochondria of the liver of rats. Soiefer and Rauckman (2001) showed that the crude extract of Anacardium occidentale caused moderate acute toxicity in rats. Moreover, Azad et al. (2013) found that the addition of CNSL in the diet for broilers fed diets containing CNSL and exposed to chronic heat stress did not result in protection against oxidative damage in muscle, indicating that the antioxidant activity may depend on the components present in the CNSL.
The compound concentration in CNSL depends on the extraction process. Natural CNSL extracted by solvents contains anacardic acid (60–65%), cardol (15–20%), cardanol (10%) and traces of 2‐methyl‐cardol (Kumar et al., 2002). In turn, technical CNSL is obtained by heating in industrial process (190–200 °C for 3 h in hot bath) of cashew nuts for human consumption (Andrade et al., 2011), resulting in decarboxylation of compounds, changing the composition of CNSL to a higher content of cardanol (83–84%), less cardol (8–11%), polymeric material remaining at 10% and traces of 2‐methyl‐cardol (Ikeda et al., 2002). An alternative way for obtaining the technical CNSL consists in heating cashew nuts for 45 min in an oven at 175 °C, reducing the process of decarboxylation due to the lower exposure to heat and resulting in a compound containing more than 49% anacardic acid (Trevisan et al., 2006).
In this sense, CNSL has aroused great interest in research studies in chemical and biological fields due to its high concentration of anacardic acid. The other components of CNSL also been highlighted in many industrial applications, but the presence of cardols and cardanols can be a problem to the use of CNSL as a source of anacardic acid, as their effects on animals are not known.
Although anacardic acid does not act as a scavenger of free radicals, the antioxidant capacity of this compound can be structured in chelating ability with metals, reducing the concentration of these in the catalysis of enzymes responsible for the peroxidation (Hemshekhar et al.