Cardanol anacardic acid

Anacardium occidentalle L. Cashew nut shell Anacardic acid, Cardanol, Brazil, Tanzania, Kenya, Nigeria... 

The structures of anacardic acid, cardol, cardanol, and 2-methyl cardol are given in Fig. 9. Each component... 

In the phenolic lipids such as the alkylphenols from Anacardium occidentals, semi-synthetic transformations have been described which exploit the functionality of the component phenols, cardanol, cardol and anacardic acid (ref. 104). A number of reactions are shown for... 

This is one of the most widely distributed plants cultivated to obtain cashew nut. The phenolic lipid is only a by-product known as cashew nut shell liquid (CNSL). The nut, attached to the base of the cashew nut apple consists of an ivory-colored kernel covered by a thin brown membrane (testa) and enclosed by an outer porous shell, the mesocarp which is about 3 mm thick with a honey-comb structure where the reddish brown liquid (CNSL) is stored [91]. The major components of CNSL are a phenolic acid, anacardic acid, a dihydric phenol, cardol with traces of mono hydric phenol, cardanol, and 2-methyl cardol [92-95]. 

AR occur in cashew nut shells as a fraction of other oil components like cardols, cardanols and anacardic acid. A comparative study on the extraction of cashew nut shell liquid (CNSL) was presented by Shobha and Ravindranath (50). The study involved the extraction of the cashew nut shell by supercritical CO2 or pentane. The pentane extraction was carried out on 50g steamed or fresh cashew nut shells in lOOmL solvent. Supercritical CO2 extraction was performed on 300g freshly broken cashew nut shells at 25 MPa and 40 C with the CO2 flow kept at 4-5Kg/h for 17,5h with extract collection every 2.5h. The resorcinolic lipid fraction obtained by supercritical CO2 represented 82% of the equivalent obtained by pentane extraction of fresh cashew nut shells and 70% of the extraction of steamed material. Despite this appreciable variation on the ratio of the total cardols and cardanols from one mediod to other, the relative proportion of the enomers in each group was very similar (50). Generally, the extraction yield obtained by supercritical CO2 was lower (= 60%) than that obtained by the classical solvent extraction methods (50), however, the product was nearly colorless. One of the major problems in the industrial application of CNSL is the very dark brown color of the solvent extracted product. 

ABSTRACT This review is concerned with non-isoprenoid phenolic lipids typified by compounds biosynthesised by the polyketide pathway. Botanical, biological and entomological sources of such phenolic lipids are described which contain monohydric phenols, notably cardanol and relatives, dihydric phenols such as cardols, alk(en)ylresorcinols,urushiols and phenolic acids, particularly anacardic acids. Some recently investigated mixed types of dihydric phenolic lipids are included. Separatory methods are briefly reviewed. Synthetic methods for the saturated and unsaturated members of the three main classes of interest in structure/activity studies are summarised. Biological properties of members of the three main classes are given and discussed. 

Early experimentation with Anacardium occidentale and cardols present in Australian species indicated that susceptibility to cardols was more prevalent than to anacardic acids or cardanols. However, more recent studies with Ginkgo biloba have found that anacardic acids were good sensitisers, while cardanols failed to induce allergic contact dermatitis [297]. 

A full biosynthetic pathway has to account for the simultaneous formation of cardol, 2-methylcardol, anacardic acid, some cardanol and for the different unsaturation pattern of anacardic acid and cardanol which are similar with a relatively low 40% of triene compared with cardol and 2-methylcardol where the the triene constituent is more than 75%. Scheme 1 summarises known ring formation stages and speculative ones. 

In the cardanol, cardol, urushiol and anacardic acid series, all of which have 8,11-unsaturation, two alternative synthons namely Cg and Cg units may be involved in alkyne routes for the formation of the second double bond. A summary is shown of alkyne, Wittig, and alkylation routes. 

Since cardanols can be obtained from anacardic acids and cardols from orsellinic acids, the methods outlined have a general applicability to a range of phenolic lipids. Reference has been made largely to the phenols of the Anacardiacae but the methods are likely to be applicable to other phenolic systems, and those with methylene-interrupted structures at different side-chain positions. Alkynes and phosphorans have both proved invaluable in synthetic studies but attention should be drawn to the very elegant use of ailenic compounds in the polyethenoid (arachidonic) series (ref. 168) which has a potential application with phenolic lipids. Methods for the synthesis of leukotrienes are also relevant for the methylene group-interrupted structures of phenolic lipids (169). 

The anacardic acids in the natural CNSL of the raw nut shell are decarboxylated and the resultant cardanol liberated supplements the hot technical CNSL in the bath through the bursting of the outer shell and, after an ideally short period, flows continuously out of the system. The spent processed nuts with the inner shell still intact also pass out of this system and after removal of the superficial CNSL by centrifugation or adsorption are shelled by an automatic procedure in Brazilian and East African technology or manually in Indian practice. 

CNSL used in polymerisation with formaldehyde as for example in friction dusts may not require elaborate analysis. Nevertheless interest in the industrial chemical uses of phenolic lipids has led to a study of quantitative methods of analysis by a variety of chromatographic methods. For cashew phenols these were first based on GLC. Thus the (15 3), (15 2), (15 1) and (15 0) constituents of methyl anacardate, cardol and cardanol have been separated by GLC on PEGA columns (ref.206), the free phenols (anacardic acid as methyl anacardate) by GLC on SE30 (ref207) and the hydrogenated anf fully methylated phenols on Dexsil and PEGA columns (ref.208). A further number of stationary phases have been investigated... 

METHOD ANACARDIC ACID CARDOL 2-METHYLCARDOL CARDANOL... 

The development of improved separational processes for obtaining pure (mixed) cardanol and cardol from technical CNSL has encouraged experimentation in chemical instead of polymer uses for these component phenols as well as for anacardic acid, by extraction from natural CNSL. Some of the earlier chemistry has been reviewed (ref. 2). Most of the more recent uses particularly for cardanol, but also cardol and anacardic add, stem from the conception of their semi-synthetic applications as readily available replenishable resources (refs. 278, 279). As with CNSL, the reactions considered in this section are concerned with the hydroxyl group of the side chain and substitution in the ring. 

Reduction of isoanacardic aldehyde gave a methylol which could also be synthesised directly from cardanol together with formation of some of the 4,6-bis-methylol. The monomethylol compound isoanacardic alcohol was an effective solvent extractant for the borate anion (ref. 279, 293). The isomeric compound, anacardic alcohol (ref. 88) was similarly obtained from anacardic acid (ref. 180). This In conjunction with the teriary amine Aliquat 336 was highly effective for the solvent extraction of the borate anion (ref. 293). Both these substances were comparable in properties to the 2,6-bis(hydroxymethyl) derivatives of 4-t nonylphenol and to 4-t octyl-2-chloro-6-hydroxymethylphenol (ref. 294). 

The extract was subjected to silica gel and alumina column chromatography to give fractions containing anacardic acid, bilobol and cardanol. Further purification with an ODS column furnished anacardic... 

They play a very important role in plants and also in plant-derived foods. They are one of the most important sources of bioactive compounds in the human diet [12], Accumulating clinical and epidemiological evidences have shown that phenolics might participate in prevention of various diseases associated with oxidative stress [13,14], Phenolic compounds could serve as a major determinant of antioxidant potential of foods because of their ability to donate a hydrogen atom or an electron in order to form stable radical intermediates. The major phenolics found in cashew are anacardic acids, cardanols, cardols, tocopherols, and other minor phenolic constituents. 

Cashew nut and its coproducts are rich sources of long-chain alkyl substituted saUcyhc add and resorcinol derivatives, namely anacardic acids, cardanols, cardols, and 2-methylcardols (Figure 10.1). The content of different alkyl substituted phenols, including anacardic adds, cardanols, and... 

FIGURE 10.1 Chemical structures of anacardic acids, cardanols, cardols, and 2-methylcardols found in cashew nut and its coproducts. 

Anacardic acids are 6-alkylsalicylic acids with different alkyl chain lengths and degrees of unsaturation. Cashew is the most important natural source of anacardic acids. Anacardic acids are found not only in cashew nut shell oil, but also in the nut and fruit juice made from cashew apple [20]. Anacardic acids are relatively nonpolar hydrophobic substances. Their structures are illustrated in Figure 10.1. They are insoluble in water, but well soluble in organic solvents such as ethanol or dimethyl sulfoxide (up to lOmg/mL). The cardanols might be formed by thermal decarboxylation of the anacardic acids [19]. 

Anacardic acid Cardol Cardanol 2-Methyl cardol... 

Meanwhile, also phenol-substituted Upids are the focus of catalytic transformations within the framework of sustainable chemistry. Typical examples are anacardic acid, cardol, 2-methylcardol, and the industrially most important compound cardanol (Figure 6.12). These phenols have preferentially Cjg side chains with a varying number of double bonds [17]. The compounds are manufactured from cashew nut oil (cashew nut shell liquid or CNSL). Currently, an annual production of450 0001 is estimated, which is continuously increasing. 

In the determination of carbamate insecticide residues, the parent phenols were coupled with diazotized p-nitroaniline and the azo dye isolated (29). In a combined TLCVGLC procedure for quantitative determination of the polyunsaturated constituents of the cashew phenols following an initial TLC separation, the eluted phenols, cardanol, 2-methylcardol, and a small proportion of anacardic acid each containing mono-, di-, and triene constituents were examined by GLC (30). 

Long-chain alkylphenols have been investigated extensively (33) by both adsorption and reversed-phase partition methods (34). The cashew phenols (from Anacardium occidentale) comprise cardanol (1), cardol (2), 2-methylcardol (3), and anacardic acid (4), each existing as a mixture of the saturated, 8 -monoene, 8 ,11 -diene, and 8 ,1 l ,14 -trieneconstituents. In ammoniated solvent [light petroleum-diethyl ether-ammonia (60 40 2)] the acidic compound anacardic acid remained practically on the baseline, whereas in an acidic solvent [light petroleum-diethyl ether-formic acid (70 30 1)] it migrated toward the solvent front as an intramolecularly bonded substance. In natural cashew nut shell liquid the phenols and their unsaturated constituents have the values 0.20 (cardol). 

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