Characterisation of alkylphenols in pistachio (Pistacia vera L.) kernels

Pistachio kernels were extracted with n-hexane and the oil obtained was saponified with methanolic KOH. The extracted unsaponifiable matter was fractionated on Thin Layer Chromatography (TLC) plates. The band with R(f) = 0.47, analysed by Gas Chromatography-Mass Spectrometry (GC-MS), showed the presence of long-chain alkylphenols: this is the first time that alkylphenols are reported in pistachio kernels. To elucidate the structures, Nuclear Magnetic Resonance (NMR) and GC-MS analyses (on the trimethylsilyl derivatives) were used. Sixteen different 3-alkylphenols (cardanols) with a saturated, monounsaturated and diunsaturated chain were detected. A reaction with dimethyl disulphide was successfully used to determine the double bond position in the monounsaturated compounds. Three phenols were new natural compounds. The most abundant cardanols were 3-(8-pentadecenyl)-phenol, 3-(10-pentadecenyl)-phenol, 3-pentadecyl-phenol and 3-(10-eptadecenyl)-phenol. Total amount of cardanols in the oils (mean of five samples) was roughly evaluated as 440 +/- 95 mg kg(-1). (C) 2009 Elsevier Ltd. All rights reserved.