Determination of the component phenols in natural and technical cashew nut-shell liquid by gas-liquid chromatography

Abstract

The component phenols In the lndustrlally useful technlcal cashew nut-shell liquid and In the natural product have untll now only been estimated. By the use of gas-llquld chromatographlc methods, they have been determined wlth much Improved preclslon. The maln dlfflcultles In the analysis lie In the widely dlfferlng proportions of the component phenols whlch exlst In different levels of unsaturatlon, and In overcoming thelr nonvolatlllty. By the use of the methyl ethers of the hydrogenated technlcal and natural products which can be quantltatlvely obtained, symmetrlcal peaks were obtained which enabled standard lntegratlon procedures to be applled and the component phenols to be quantltatlvely determined. The method Is quicker to operate than any preceding method. On polyethylene glycol adlpate columns, the mean results (wlth standard devlatlons) for the CIS phenols In natural cashew nut-shell llquld were 82.0 f 1.05% anacardlc acid, 13.8 f 0.79% cardol, 2.6 f 0.16% 2-methylcardol and 1.6 f 0.17% cardanol. For technical cashew nut-shell liquid, the mean results were 83.0 f 0.51% cardanol, 14.3 f 0.58% cardol, 2.7 f 0.34% 2-methylcardol. The principal component phenols in cashew nut-shell liquid (CNSL) from Anacardium occidentale are anacardic acid (I, R1 = R2 = R3 = H, R4 = C02H, n = 0, 2,4,6) (1-3), cardol (I, R2 = R3 = Rq = H, R1 = OH, n = 0, 2, 4, 6) ( 4 ) , 2-methylcardol (I, Rs = R4 = H, R1 = OH, R2 = CH3, n = 0, 2, 4,6) (5, 6 ) , and cardanol (I, R1 = R2 = R3 = R4 = H, n = 0, 2, 4, 6) (7).The natural product is thermally decarboxylated to yield the industrially useful (8, 9) "technical CNSL", containing mainly cardanol. The initial column chromatographic separations of cardanol methyl ether from methylated technical CNSL on alumina and its subsequent resolution on, a more active column into the saturated, monoene, diene, and triene constituents were described by Symes and Dawson (7). Technical CNSL has been separated on silica gel (8) and also natural CNSL (9) after removal of anacardic acid by the lead salt procedure and by preliminary passage through alumina (6). Column chromatographic methods have, however, tended to be estimations rather than determinations of the phenolic composition. Other physical techniques used have been argentation TLC ( 3 ) and, less effectively, low temperature crystallization (2).An adsorption thin layer chromatographicluv spectrophotometric method was effective for determination of the phenolic composition of natural CNSL (5), although technical CNSL caused difficulties.A gas-liquid chromatographic determination with the stationary phase SE-30 has been employed for technical and natural CNSL after hydrogenation of the unsaturated side chains and conversion of (15:O) anacardic acid to the volatile methyl ester (10). Insufficient resolution of (15:O) cardol and 2-methylcardol and skewed peaks has led to the desirability of converting all the (150) phenols to volatile derivatives. A variety of these have been examined and this present account is concerned with the (15:O) methyl e...

Anacardiaceae Lindl.

“…Disease Genesis-The caustic oil of Anacardium is composed of approximately 82% anacardic acid, 13.8% cardol, 2.6% 2 -methyl cardol, and 1.6% cardanol (Tyman 1976). The irritant and allergenic potency ranges in descending order from cardol to anacardic acid and anacardols (Keil et al 1945a;Wasserman and Dawson 1948).…”

Compositional studies on technical cashew nutshell liquid (cnsl) by chromatography and mass spectroscopy

“…Methylation: Methylation was carried out as described (11). The filtered reaction mixture was thoroughly washed 663 664 JOURNAL OF THE AMERICAN OIL CHEMISTS' SOCIETY with water and concentrated to give an approximately 10% solution of the methyl ether.…”

“…Thin layer chromatography was carried out as described (11,13) on Kieselgel G (Merck). All separated component phenols for GLC or MS examination were stored until required in tightly stoppered containers at -20 C. C, 100-t20; 5% SE52, Diatomite C, 100-120; 3% OV17, Diatomite M, 60-80; 3% Dexsil 300, Diatomite M, 60-80; 3% PEGA, Diatomite M, 60-80; 5% APL, Diatomite M, 60-80.…”

“…The original GLC procedure (11) for quantitative analysis of the unsaturated constituents of the component phenols as methyl ethers on 2% PEGA is more time consuming for the examination of a range of samples than a recently developed procedure (13) based on mass spectroscopy (MS) which shows close agreement (15).…”

“…Early work based on thin layer chromatorgraphy (TLC) combined with ultraviolet spectrophotometry for the analysis of component phenols of natural CNSL proved difficult to apply quantitatively to technical CNSL (10). Gas liquid chromatography (11) of the hydrogenated and methylated component phenols was found useful for natural and technical CNSL, and the four constituents (n = 0,2,4,6,I,II,III,IV) of each component phenol, separated by preliminary TLC, were then determined by GLC (12) and later by mass spectroscopy (13).…”